added whole content

2025-05-04 15:26:41 +07:00 · 2022-11-03 10:38:11 +06:00 · 2022-11-03 10:38:11 +06:00 · dd104eed49
commit dd104eed49
parent 07a306a6f4
70 changed files with 5962 additions and 19 deletions
--- a/content/Blockchain/Common
+++ b/content/Blockchain/Common
@ -0,0 +1,192 @@
+- Simple #dapp example for tests: [https://metamask.github.io/test-dapp/](https://metamask.github.io/test-dapp/)
+- Interaction with smart contracts described in [Smart contracts](Smart%20contracts.md)
+
+## Connecting to node
+
+If #Metamask extension installed, `Web3.givenProvider` is available in global window. You can use [Infura](https://infura.io) or your node instead:
+
+```typescript
+import Web3 from 'web3';
+
+// URL of your node
+const PROVIDER_URL = 'https://...';
+
+export const web3 = new Web3(Web3.givenProvider || PROVIDER_URL);
+``` 
+
+## Getting wallet balance
+
+```typescript
+const getBalance = async (address: string) => {
+    return await web3.eth.getBalance(address);
+}
+```
+
+## Getting wallet address
+
+```typescript
+// first we need to authorize
+const authorize = async () => {
+  await web3.currentProvider.request({ method: 'eth_requestAccounts' });
+}
+
+// then we can get wallet address
+const getCurrentAddressUser = () => {
+    return web3.currentProvider.selectedAddress;
+}
+```
+
+## Sending transaction
+
+Sending `value` tokens with `memo` as value:
+
+```typescript
+
+const transfer = async ({ 
+  from, 
+  to, 
+  value, 
+  memo, 
+  privateKey, 
+  gasLimit = 44000 
+}) => {
+    const nonce = await web3.eth.getTransactionCount(from);
+    const gasPrice = await web3.eth.getGasPrice();
+    
+    const rawTx = {
+      from,
+      to,
+      value: web3.utils.toHex(Web3.utils.toWei(value, 'ether')),
+      gasLimit: web3.utils.toHex(gasLimit),
+      gasPrice: web3.utils.toHex(gasPrice),
+      nonce: web3.utils.toHex(nonce),
+      data: memo,
+    };
+    
+    const privateKeyBuffer = EthUtil.toBuffer(privateKey);
+    
+    const tx = new Transaction(rawTx);
+    
+    tx.sign(privateKeyBuffer);
+    const serializedTx = tx.serialize();
+    
+    return this.web3.eth.sendSignedTransaction(
+      `0x${serializedTx.toString('hex')}`
+    );
+}
+```
+
+## Estimating transaction FEE
+
+Useful to get fixed amount of tokens from user with pre-estimated fee.
+
+```typescript
+import { web3 } from '.';
+
+const estimateFee = async ({
+    from,
+    to,
+    value,
+    memo,
+}) => {
+    const gasPrice = await web3.eth.getGasPrice();
+    const gasLimit = await web3.eth.estimateGas({
+      from,
+      to,
+      value: web3.utils.toHex(web3.utils.toWei(value, 'ether')),
+      data: web3.utils.asciiToHex(memo),
+    }).call();
+    
+    return web3.utils.fromWei(
+      BigInt(gasPrice.toString())
+        .multiply(BigInt(gasLimit.toString()))
+        .toString()
+    );
+}
+```
+
+## Subscribing to wallet address change
+
+```typescript
+import { web3 } from '.';
+
+web3.currentProvider.on('accountsChanged', callback);
+```
+
+
+## Watching network change
+
+```typescript
+ethereum.on('chainChanged', handler: (chainId: string) => void);
+```
+
+## Adding custom token to wallet
+
+```typescript
+window.ethereum
+  .request({
+    method: 'wallet_watchAsset',
+    params: {
+      type: 'ERC20',
+      options: {
+        address: '0xb60e8dd61c5d32be8058bb8eb970870f07233155',
+        symbol: 'FOO',
+        decimals: 18,
+        image: 'https://foo.io/token-image.svg',
+      },
+    },
+  })
+  .then((success) => {
+    if (success) {
+      console.log('FOO successfully added to wallet!')
+    } else {
+      throw new Error('Something went wrong.')
+    }
+  })
+  .catch(console.error)
+  ```
+
+## Changing network to custom 
+
+Checking current chainId:
+
+```typescript
+const getChainID = async () => {
+    return ethereum.request({ method: 'eth_chainId' })
+}
+```
+
+Asking wallet to change current network:
+
+```typescript
+try {
+  await window.ethereum.request({
+    method: 'wallet_switchEthereumChain',
+    params: [{ chainId: '0x03' }], // ropsten chainID (3) in hex
+  });
+} catch (switchError) {
+  // This error code indicates that the chain has not been added to MetaMask.
+  if (error.code === 4902) {
+    try {
+      await window.ethereum.request({
+        method: 'wallet_addEthereumChain',
+        params: [{ 
+          chainId: '0x03', // ropsten chainID (3) in hex
+          chainName: 'Ropsten Test Network', 
+          nativeCurrency: { 
+              name: 'ETH',
+              symbol: 'ETH',
+              decimals: 18
+          }, 
+          rpcUrls: ['https://ropsten.infura.io/v3/9aa3d95b3bc440fa88ea12eaa4456161'], 
+          blockExplorerUrls: ['https://ropsten.etherscan.io'] 
+        }] ,
+      });
+    } catch (addError) {
+      // handle "add" error
+    }
+  }
+  // handle other "switch" errors
+}
+```
+
--- a/content/Blockchain/Smart
+++ b/content/Blockchain/Smart
@ -0,0 +1,248 @@
+For common functions see [Common typescript examples](Common%20typescript%20examples.md). 
+
+## Getting smart contract instance
+
+Useful for calling smart contract methods:
+
+```typescript
+import { Contract } from 'web3-eth-contract';
+import { web3 } from '.';
+
+const getContract = (abi: object, address?: string): Contract => {
+  const abiFromJson = JSON.parse(JSON.stringify(abi));
+  return new web3.eth.Contract(abiFromJson, address);
+};
+
+export default getContract;
+```
+## Executing contract method
+
+Contract has **read** and **write** methods. To get a list of methods, you can paste contract address on  [https://etherscan.io/ ETH](https://etherscan.io/token/0xdac17f958d2ee523a2206206994597c13d831ec7#readContract) or any other service.
+
+ **Read** methods doesn't require spending **gas**. **Write** methods cost some amount of **gas**, hence they will be executed with confirmation from user.
+
+### Example for #Metamask without private key
+
+```typescript
+// see example below
+import { getContract } from '.';
+
+// ABI of contract
+const CONTRACT_ABI = { /* ... */ };
+ // address for contract
+const CONTRACT_ADDRESS = '0xdea164f67df4dbfe675d5271c9d404e0260f33bb';
+
+export const executeContractMethod = async ({}) => {
+  // getting contract
+  const contract = getContract(CONTRACT_ABI, CONTRACT_ADDRESS);
+  
+  // Calling write method
+  try {
+    // authorizing with Metamask
+    await web3.currentProvider.request({ method: 'eth_requestAccounts' });
+    // getting wallet address
+    const addressUser = web3.currentProvider.selectedAddress;
+    // calling "store" store method for contract
+    // payload should include `from` address, that matches
+    // current user's wallet
+    await contract.methods.store(0, 'Parameter').send({
+      from: addressUser,
+    });
+  } catch (e) {
+    throw new Error(e);
+  }
+  
+  // calling read method
+  try {
+    // this method can return data
+    const result = await contract.methods.retrieve().call();
+  } catch (e) {
+    throw new Error(e);
+  }
+}
+```
+
+### Node.js and React Native example
+
+```typescript
+// see example below
+import { getContract } from '.';
+
+// ABI контракта
+const CONTRACT_ABI = { /* ... */ };
+// contract address
+const CONTRACT_ADDRESS = '0xdea164f67df4dbfe675d5271c9d404e0260f33bb';
+// getting contract
+const contract = getContract(CONTRACT_ABI, CONTRACT_ADDRESS);
+// account's private key
+const privateKey = '...';
+
+// write-methods requires private key
+const executeContractMethod = async (val: number) => {
+    const transaction = contract.methods.store(val);
+    const account = web3.eth.accounts.privateKeyToAccount(privateKey);
+    const options = {
+      to: CONTRACT_ADDRESS,
+      data: transaction.encodeABI(),
+      gas: await transaction.estimateGas({ from: account.address }),
+      gasPrice: await web3.eth.getGasPrice(),
+    };
+    const signed = await web3.eth.accounts.signTransaction(
+      options,
+      privateKey,
+    );
+    await web3.eth.sendSignedTransaction(signed.rawTransaction!);
+};
+```
+
+### Calling a batch of contract's methods
+
+Function calls batch of requests, returning array of results. For example:
+
+```typescript
+  const requests = [
+   contract.method.balanceOf().call,
+   contract.method.getStaked().call
+  ]
+
+  const result = await makeBatchRequest(request);
+```
+
+```typescript
+const web3 = new Web3(Web3.givenProvider || PROVIDER_URL);
+
+const makeBatchRequest = (calls: any[]) => {
+  try {
+    const web3 = getWeb3NoAccount();
+    const batch = new web3.BatchRequest();
+
+    const promises = calls.map((call) => {
+      return new Promise((resolve, reject) => {
+        batch.add(
+          call.request({}, (err, result) => {
+            if (err) {
+              reject(err);
+            } else {
+              resolve(result);
+            }
+          })
+        );
+      });
+    });
+
+    batch.execute();
+
+    return Promise.all(promises);
+  } catch {
+    return null;
+  }
+};
+
+export default makeBatchRequest;
+```
+
+## Subscribing to smart contract events
+
+There're different ways to subscribe for contract events. For all of them you will need following variables:
+
+```typescript
+  import Web3 from 'web3';
+  const web3 = new Web3('YOUR_RPC_ENDPOINT_HERE');
+  const ABI = 'YOUR ABI HERE';
+  const CONTRACT_ADDRESS = 'YOUR CONTRACT ADDRESS HERE';
+  const myContract = new Web3.Contract(ABI, CONTRACT_ADDRESS);
+```
+
+### By accessing contract.events
+
+```typescript
+referralProgramContract.events
+  .RegisterUser()
+  .on('connected', (subscriptionId: string) => {
+    console.log(`| UserRegistered | events | ${subscriptionId}`);
+  })
+  .on(
+    'data',
+    async (event: {
+      removed: boolean;
+      returnValues: RegisterUserResponseInterface;
+    }) => {
+      try {
+        if (event.removed) {
+          return;
+        }
+        const { user, referrer } = event.returnValues;
+        console.log(user, referrer);
+      } catch (e) {
+        console.log(`| ONCE | ${e}`);
+      }
+    },
+  )
+  .on('error', (error: ErrnoException) => {
+    console.log(error);
+  });
+```
+
+### With filtering
+
+We're listening to `Transfer` event here:
+
+```typescript
+  let options = {
+    filter: {
+        value: [],
+    },
+    fromBlock: 0
+  };
+
+  myContract.events.Transfer(options)
+    .on('data', event => console.log(event))
+    .on('changed', changed => console.log(changed))
+    .on('error', err => throw err)
+    .on('connected', str => console.log(str))
+```
+
+### Common Subscribe method
+
+Filtering options can also be specified:
+
+```typescript
+  let options = {
+    fromBlock: 0,
+    address: ['address-1', 'address-2'],    //Only get events from specific addresses
+    topics: []                              //What topics to subscribe to
+  };
+
+  let subscription = ('logs', options, (err,event) => {
+      if (!err)
+      console.log(event)
+  });
+
+  subscription.on('data', event => console.log(event))
+  subscription.on('changed', changed => console.log(changed))
+  subscription.on('error', err => { throw err })
+  subscription.on('connected', nr => console.log(nr))
+```
+
+### Getting event history
+
+Getting history for `Transfer` events for specific values. More info can be found [here](https://web3js.readthedocs.io/en/v1.2.11/web3-eth-subscribe.html#)
+
+```typescript 
+  //example options(optional)
+  let options = {
+    filter: {
+        // only get events where transfer value was 1000 or 1337
+        value: ['1000', '1337']    
+    },
+    // number | "earliest" | "pending" | "latest"
+    fromBlock: 0,                  
+    toBlock: 'latest'
+  };
+
+  myContract.getPastEvents('Transfer', options)
+    .then(results => console.log(results))
+    .catch(err => throw err);
+
+```
+
--- a/content/CSS/Automatic
+++ b/content/CSS/Automatic
@ -0,0 +1,45 @@
+Grid, that places items by density. Pure #css solution. Can be used with items, that take different amount of rows/columns.
+
+```scss
+$cell: 250px;
+$gap: 20px;
+
+.grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax($cell, 1fr));
+  grid-auto-rows: 256px;
+  grid-auto-flow: row dense;
+  grid-column-gap: $gap;
+  grid-row-gap: $gap;
+}
+```
+
+### Basic elements with double height or width
+
+```scss
+.h-2 { // takes 2 columns
+	grid-column-end: span 2;
+}
+
+.v-2 { // takes 2 rows
+	grid-row-end: span 2;
+}
+```
+
+### Header, that fills all columns
+
+```scss
+.full-width {
+  grid-row: 1 / 2; // height: 1 row
+  grid-column: 1 / -1;
+}
+```
+
+### Stamp element, that takes 3 rows in the top right corner
+
+```scss
+.top-right {
+  grid-row: 1 / 3; // height here
+  grid-column: -2 / -1; // width here
+}
+```
--- a/content/CSS/Sass
+++ b/content/CSS/Sass
@ -0,0 +1,19 @@
+Say, we need to color `n` items by specific colors, which depend on its position. #SCSS supports [iteration over lists](https://sass-lang.com/documentation/at-rules/control/each) for that purposes:
+
+```scss
+@mixin color-per-child($colors) {
+  @each $color in $colors {
+    &:nth-child(#{index(($colors), ($color))}) {
+      color: $color;
+    }
+  }
+}
+```
+
+Usage is simple:
+
+```scss
+.item {
+  @include color_per_child((#ded187, #dbde87, #bade87, #9cde87, #87deaa));
+}
+```
--- a/content/CSS/Test
+++ b/content/CSS/Test
@ -0,0 +1,20 @@
+To test if browser supports some #CSS rules, do following:
+
+```css
+@supports (backdrop-filter: blur(5px)) {
+	backdrop-filter: blur(5px);
+}
+```
+
+This `@mixin` will only apply rule if browser support backdrop filtering:
+
+```scss
+@mixin can_backdrop {
+  @supports (
+    (-webkit-backdrop-filter: blur(5px)) or 
+    (backdrop-filter: blur(5px))
+  ) {
+    @content;
+  }
+}
+```
--- a/content/Docker/Building
+++ b/content/Docker/Building
@ -0,0 +1,15 @@
+Sample #Dockerfile for static Typescript builds such a #nextjs, #gatsby or #nuxt:
+
+```Dockerfile
+FROM node:16-alpine as builder
+WORKDIR /app
+COPY package.json yarn.lock ./
+RUN yarn
+COPY . .
+
+# your generate command here
+RUN yarn generate
+
+FROM nginx
+COPY --from=builder /app/dist /usr/share/nginx/html
+```
--- a/content/Docker/Drone-ci.md
+++ b/content/Docker/Drone-ci.md
@ -0,0 +1,98 @@
+Can be used with [Private docker registry](Private%20docker%20registry.md) to deploy things using #docker.
+
+## Pushing to private docker_registry
+
+You should specify `global_docker_login`, `global_docker_password`, `global_docker_registry` organizations variables in your **drone**. And `docker_repo` variable for your repo as `docker.yourdomain.com/your-image`.
+
+This is example of  `.droneci` for [private docker registry](Private%20docker%20registry.md): 
+
+```yaml
+kind: pipeline
+name: build
+type: docker
+
+platform:
+  os: linux
+  arch: amd64
+
+steps:
+  - name: build-master
+    image: plugins/docker
+    when:
+      branch:
+        - master
+    settings:
+      dockerfile: Dockerfile
+      tag:
+        - ${DRONE_BRANCH}
+      username:
+        from_secret: global_docker_login
+      password:
+        from_secret: global_docker_password
+      registry:
+        from_secret: global_docker_registry
+      repo:
+        from_secret: docker_repo
+```
+
+## Docker-compose file for drone-ci
+
+The `drone` service is ui itself and `drone-agent` is runner for builds, that can be started on different machine (or machines).
+
+Change `secret_id`, `rpc_secret` and `drone.url` to something you like.
+
+```yaml
+version: "3"
+
+services:
+  drone:
+    container_name: drone
+    image: drone/drone:latest
+    environment:
+      - DRONE_GITHUB_CLIENT_ID=secret_id
+      - DRONE_GITHUB_CLIENT_SECRET=client_secret
+      - DRONE_RPC_SECRET=rpc_secret
+      - DRONE_SERVER_HOST=drone.url
+      - DRONE_USER_CREATE="username:user,admin:true"
+      - DRONE_SERVER_PROTO=https
+      - DRONE_TLS_AUTOCERT=false
+      - DRONE_GIT_ALWAYS_AUTH=false
+      - DRONE_LOGS_DEBUG=true
+      - DRONE_LOGS_TRACE=true
+    restart: always
+    volumes:
+      - ./data:/data
+    ports:
+      - 8090:80
+  drone-agent:
+    container_name: drone__agent
+    image: drone/agent:latest
+    command: agent
+    restart: always
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+    environment:
+      - DRONE_RPC_SERVER=https://drone.url
+      - DRONE_RPC_SECRET=rpc_secret
+```
+
+## Caching builds
+
+Haven't checked that yet, but there's a [manual](https://laszlo.cloud/the-ultimate-droneci-caching-guide) from [Laszlo Fogas](https://laszlo.cloud/) about that.
+
+## Get user info
+
+```shell
+export DRONE_SERVER=https://drone.url
+export DRONE_TOKEN=password
+drone info
+```
+
+## Mark user as trusted
+
+Sometimes it won't help, then connect to drone database with sqlite and change user's trusted flag to `1`.
+
+```shell
+drone repo update $1 --trusted=true && drone repo info $1
+```
+
--- a/content/Docker/Github
+++ b/content/Docker/Github
@ -0,0 +1,44 @@
+To deploy github pages with [Drone-ci](Drone-ci.md) you will need `.drone.yml` as specified below. You also should define secrets  `github_username` and `github_token` (get it [here](https://github.com/settings/tokens)) in your drone's repository setup.
+
+Github repository should be named as `yourname.github.io` and it could be accessed at https://yourname.github.io/. Otherwise it'll be available at https://yourname.github.io/repo-name/, what you might not like.
+
+You should create branch named `gh-pages` in that repo and setup GH Pages at `https://github.com/<yourusername>/<yourusername>.github.io/settings/pages`.
+
+This config will update `gh-pages` branch in your project, which will contain only generated content. I know, that's bad, but there's no better way to do that with generic drone plugins.
+
+```yaml
+kind: pipeline
+name: build
+type: docker
+
+platform:
+  os: linux
+  arch: amd64
+
+steps:
+  - name: build
+    image: node:16
+    commands:
+      - yarn
+      - yarn generate
+      - rm -rf ./docs
+      - mv ./.output/public ./docs
+      - touch ./docs/.nojekyll
+  - name: publish
+    image: plugins/gh-pages
+    settings:
+      target_branch: gh-pages
+      username:
+        from_secret: github_username
+      password:
+        from_secret: github_token
+```
+
+Here we're moving `./.output/public` to `./docs`, because #nuxt creates symlink for `docs` and git can't work with that.
+
+Also we create `.nojekyll` at the root of repo, so github's internal engine won't [ignore files that start with underscore](https://github.blog/2009-12-29-bypassing-jekyll-on-github-pages/).
+
+## Additional reading
+
+- [Drone Github Pages Documentation](https://plugins.drone.io/plugins/gh-pages)
+- [Bypassing Jekyll on GitHub Pages](https://github.blog/2009-12-29-bypassing-jekyll-on-github-pages/)
--- a/content/Docker/Private
+++ b/content/Docker/Private
@ -0,0 +1,71 @@
+Suitable to work with [Drone-ci](Drone-ci.md) for hosting private #docker images.
+
+## Sample docker-compose for custom docker registry
+
+This one brings up private docker registry with ui. First you'll need to generate password for it:
+
+```shell
+docker run \
+  --entrypoint htpasswd registry:2 \
+  -Bbn user mypassword > auth/registry.password
+```
+
+```yaml
+version: "3"
+services:
+  registry:
+    container_name: docker__registry
+    image: registry:2
+    ports:
+    - 5000:5000
+    restart: always
+    environment:
+      - REGISTRY_STORAGE_FILESYSTEM_ROOTDIRECTORY=/data
+      - REGISTRY_AUTH=htpasswd
+      - REGISTRY_AUTH_HTPASSWD_REALM=Registry
+      - REGISTRY_AUTH_HTPASSWD_PATH=/auth/registry.password
+      - REGISTRY_HTTP_SECRET=password
+      - REGISTRY_STORAGE_DELETE_ENABLED=true
+    volumes:
+      - ./registry/auth:/auth
+      - ./registry/data:/data
+  ui:
+    container_name: docker__ui
+    image: parabuzzle/craneoperator:latest
+    ports:
+    - 80:80
+    restart: always
+    environment:
+      - REGISTRY_HOST=registry
+      - REGISTRY_PORT=5000
+      - REGISTRY_PROTOCOL=http
+      - ALLOW_REGISTRY_LOGIN=true
+      - REGISTRY_ALLOW_DELETE=true
+      - USERNAME=registry
+      - PASSWORD=password
+```
+
+## Squash layers on registry
+
+Sometimes you need to squash all layers in docker registry to free up disk space.
+
+1. Run this command to mark oldest layers
+
+```shell
+# Try this first
+docker run \
+  --rm anoxis/registry-cli \
+  -r https://registry.url \
+  -l user:password \
+  --delete \
+  --num 2
+
+# Then this 
+docker run -it \
+    -v /path/to/registry/data:/registry \
+    -e REGISTRY_URL=https://registry.url \
+    -e DRY_RUN="false" \
+    -e REGISTRY_AUTH="user:password" \
+    mortensrasmussen/docker-registry-manifest-cleanup
+```
+
--- a/content/Docker/Refresh
+++ b/content/Docker/Refresh
@ -0,0 +1,17 @@
+## Setting up watchtower 
+
+[Watchtower](https://containrrr.dev/watchtower/) will automatically pull updated #docker containers. Can be used with [Private docker registry](Private%20docker%20registry.md) and [Drone-ci](Drone-ci.md).
+
+```yaml
+version: "3"
+
+services:
+  watchtower:
+    container_name: docker__watchtower
+    image: v2tec/watchtower
+    restart: always
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+      - /home/user/.docker/config.json:/config.json
+    command: --interval 60 image_1 image_2
+```
--- a/content/Docker/Seed
+++ b/content/Docker/Seed
@ -0,0 +1,15 @@
+If you need to seed `.sql` dump in #docker container, just run this command. Also you can try to [rsync file with SSH](/linux/Rsync%20file%20with%20SSH) to get it from remote host.
+
+```shell
+#####
+# usage: ./script.sh "/path/to/dump.sql"
+#####
+
+DUMP_PATH=$1
+CONTAINER="db"
+USER=root
+PASSWORD=password
+DB=database
+
+cat "$DUMP_PATH" | docker exec -i $CONTAINER mysql -u$USER -p$PASSWORD $DB
+```
--- a/content/Docker/Wait
+++ b/content/Docker/Wait
@ -0,0 +1,29 @@
+[wait-for-it.sh](https://github.com/vishnubob/wait-for-it) doing a great job of waiting for different services to become alive, but on #MacOs #docker is binding port on container start, seconds before #mysql is ready to accept connections
+
+This script waits for first successful query from database or exits with non-zero status after timeout.
+
+Don't forget to change `$query` for the actually working one.
+
+```shell
+# Waits for mysql to become actually available
+wait_for_mysql() {
+  query="SELECT count(*) FROM users"
+  
+  timeout=180 # 3 minutes limit
+  i=0
+  
+  while ! docker exec -it "$1" mysql --user="$2" --password="$3" -e "$query" $4 >/dev/null 2>&1; do
+    sleep 1;
+
+    i=$(($i+1))
+    if [[ ${i} -ge ${timeout} ]]; then
+      echo "[Error] can't properly query MySQL after ${i} secs"
+      exit 1;
+    fi
+  done
+}
+
+# usage: wait_for_mysql miin-mysql-dev root password database
+```
+
+[Wait for redis](Wait%20for%20redis.md)
--- a/content/Docker/Wait
+++ b/content/Docker/Wait
@ -0,0 +1,24 @@
+[wait-for-it.sh](https://github.com/vishnubob/wait-for-it) doing a great job of waiting for different services to become alive, but on #MacOs #docker is binding port on container start, seconds before redis is ready to accept connections
+
+This script waits for first successful ping or exits with non-zero status after 3 minutes.
+
+```shell
+# Waits for redis to become actually available
+wait_for_redis() {
+  timeout=180 # 3 minutes
+  i=0
+  while ! docker exec -it "$1" redis-cli -h localhost -p 6379 -a "$2" ping | grep "PONG" >/dev/null 2>&1; do
+    sleep 1;
+
+    i=$(($i+1))
+    if [[ ${i} -ge ${timeout} ]]; then
+      echo "[Error] can't properly ping Redis container after ${i} secs"
+      exit 1;
+    fi
+  done
+}
+
+# usage: wait_for_redis miin-redis-dev password
+```
+
+[Wait for mysql](Wait%20for%20mysql.md)
--- a/content/Frontend/React
+++ b/content/Frontend/React
@ -0,0 +1,48 @@
+Use #oauth2 login with React-Native
+
+## Common OAuth2 providers
+
+Can be handled by [react-native-app-auth](react-native-app-auth) by redirecting to url `com.yourapp://oauth2provider`. 
+
+### Example for #Google
+
+```typescript
+import { authorize } from 'react-native-app-auth';
+
+const GOOGLE_OAUTH_CLIENT = '...';
+
+// ...
+const authState = await authorize({
+  issuer: 'https://accounts.google.com',
+  clientId: `${GOOGLE_OAUTH_CLIENT}.apps.googleusercontent.com`,
+  redirectUrl: `com.yourapp:/oauth2redirect/google`,
+  scopes: ['openid', 'profile'],
+  dangerouslyAllowInsecureHttpRequests: true,
+});
+```
+
+### Example for #Yandex
+
+```typescript
+const YANDEX_OAUTH_CLIENT = '...';
+const YANDEX_OAUTH_SECRET = '...'; // better hide it somehow
+const APP_ID = 'com.yourapp';
+
+const authState = await authorize({
+  serviceConfiguration: {
+    authorizationEndpoint: `https://oauth.yandex.ru/authorize?response_type=code&client_id=${YANDEX_OAUTH_CLIENT}&redirect_uri=${APP_ID}:/oauth2redirect`,
+    // TODO: replace it with your own backend to secure client_secret:
+    tokenEndpoint: `https://oauth.yandex.ru/token?grant_type=authorization_code&client_id=${YANDEX_OAUTH_CLIENT}&client_secret=${YANDEX_OAUTH_SECRET}`,
+  },
+  clientId: YANDEX_OAUTH_CLIENT,
+  redirectUrl: `${APP_ID}:/oauth2redirect`,
+  scopes: ['login:info', 'login:avatar'],
+  dangerouslyAllowInsecureHttpRequests: true,
+});
+
+callback(authState.accessToken);
+```
+
+## Apple ID login
+
+[react-native-apple-authentication](https://github.com/invertase/react-native-apple-authentication) has its own [documentation](https://github.com/invertase/react-native-apple-authentication/tree/main/docs) on setting up OAuth using Apple ID.
--- a/content/Frontend/React
+++ b/content/Frontend/React
@ -0,0 +1,60 @@
+Sometimes you need to keep scroll position of `FlatList` in React Native after some user interactions.
+
+```typescript
+// interact() is doing some stuff, that changes FlatList scroll size
+type Props = { interact: () => void; }
+
+const SomeList: FC<Props> = ({ interact }) => {
+  const scrollPosition = useRef(0);
+  const scrollHeight = useRef(0);
+  
+  // set it to `true` before interaction and back to `false` right after
+  const shouldKeepScrollPosition = useRef(false);
+
+  const onScroll = useCallback(
+    (event: NativeSyntheticEvent<NativeScrollEvent>) => {
+      scrollPosition.current = event.nativeEvent.contentOffset.y;
+    },
+    [],
+  );
+
+  const onContentSizeChange = useCallback((_: number, h: number) => {
+    if (!shouldKeepScrollPosition.current) {
+      scrollHeight.current = h;
+      return;
+    }
+
+    ref.current?.scrollToOffset({
+      offset: scrollPosition.current + (h - scrollHeight.current),
+      animated: false,
+    });
+
+    scrollHeight.current = h;
+  }, []);
+
+  // onInteraction wraps interaction to preserve scroll position
+  const onInteraction = useCallback(
+    () => {
+      shouldKeepScrollPosition.current = true;
+
+      setTimeout(() => {
+        interact();
+      }, 0);
+
+      setTimeout(() => {
+        shouldKeepScrollPosition.current = false;
+      }, 500);
+    },
+    [setSelectedSubThemes],
+  );
+  
+  return (
+    <FlatList
+      // ...required FlatList options
+      ref={ref}
+      onContentSizeChange={onContentSizeChange}
+      onRefresh={onRefresh}
+      onScroll={onScroll}
+    />
+  )
+}
--- a/content/Frontend/React
+++ b/content/Frontend/React
@ -0,0 +1,65 @@
+## Show android logcat
+
+```shell
+adb logcat com.application:I "*:S"
+```
+
+## Get .apk's SHA-256 
+
+```bash
+keytool -printcert -jarfile "$1"
+```
+
+## Assemble debug release on Android
+
+Packages release with bundled resources. 
+
+```shell
+npx react-native bundle \
+  --platform android \
+  --dev false \
+  --entry-file index.js \
+  --bundle-output android/app/src/main/assets/index.android.bundle \
+  --assets-dest android/app/src/main/res/
+
+cd android && ./gradlew assembleDebug
+
+# do your stuff
+
+./gradlew clean
+```
+
+## Send release to Android device
+
+```shell
+cd ./android \
+  && ./gradlew assembleRelease \
+  && adb install ./app/build/outputs/apk/release/app-release.apk
+```
+
+## Deep links
+
+- https://zarah.dev/2022/02/08/android12-deeplinks.html
+- https://developer.android.com/training/app-links/verify-site-associations#invoke-domain-verification
+- https://digitalassetlinks.googleapis.com/v1/statements:list?source.web.site=https://miin.ru&relation=delegate_permission/common.handle_all_urls
+
+### Open deep links
+
+```shell
+# ios 
+xcrun simctl openurl booted $1
+
+# android
+adb shell am start -W -a android.intent.action.VIEW -d $1 \
+com.application
+```
+
+### Reverify links on Android
+
+```shell
+PACKAGE="com.application"
+
+adb shell pm set-app-links --package $PACKAGE 0 all && \
+  adb shell pm verify-app-links --re-verify $PACKAGE
+```
+
--- a/content/Frontend/React/Axios
+++ b/content/Frontend/React/Axios
@ -0,0 +1,106 @@
+`<ApiProvider />` component, that will handle token refresh if needed. Refresh function should, probably, be passed through component props.
+
+```typescript
+import axios from "axios";
+import React, {
+  createContext,
+  FC,
+  PropsWithChildren,
+  useCallback,
+  useContext,
+  useEffect,
+  useRef,
+} from "react";
+
+interface APIProviderProps extends PropsWithChildren {
+  tokens: {
+    access: string;
+    refresh: string;
+  };
+  logout: () => void;
+}
+
+const APIContext = createContext({
+  client: axios.create({
+    baseURL: process.env.NEXT_PUBLIC_API_ENDPOINT,
+  }),
+});
+
+const APIProvider: FC<APIProviderProps> = ({ 
+	tokens, 
+	logout, 
+	children,
+}) => {
+  const client = useRef(
+    axios.create({
+      baseURL: process.env.NEXT_PUBLIC_API_ENDPOINT,
+    })
+  ).current;
+
+  const refreshTokens = useCallback<() => string>(() => {
+    // TODO: implement me
+    throw new Error("not implemented");
+  }, []);
+
+  useEffect(() => {
+    if (!tokens.access) {
+      return;
+    }
+
+    // append `access` token to all requests
+    const req = client.interceptors.request.use(
+      async (config) => {
+        config.headers = {
+          Authorization: `Bearer ${tokens.access}`,
+        };
+        return config;
+      },
+      (error) => {
+        Promise.reject(error);
+      }
+    );
+
+    // refreshing interceptor
+    const resp = client.interceptors.response.use(
+      (response) => {
+        return response;
+      },
+      async function (error) {
+        const originalRequest = error.config;
+
+        if (error.response.status === 401 && !originalRequest._retry) {
+          originalRequest._retry = true;
+
+          const newToken = refreshTokens;
+
+          return axios({
+            ...originalRequest,
+            headers: {
+              ...originalRequest.headers,
+              Authorization: "Bearer " + newToken,
+            },
+          });
+        }
+
+        logout();
+        return Promise.reject(error);
+      }
+    );
+
+    return () => {
+      axios.interceptors.request.eject(req);
+      axios.interceptors.request.eject(resp);
+    };
+  }, [client, tokens.access, tokens.refresh, refreshTokens, logout]);
+
+  return (
+    <APIContext.Provider value={{ client }}>
+	    {children}
+    </APIContext.Provider>
+  );
+};
+
+export const useAPI = () => useContext(APIContext).client;
+
+export { APIProvider };
+```
--- a/content/Frontend/React/Axios
+++ b/content/Frontend/React/Axios
@ -0,0 +1,32 @@
+If you need to cancel some request, use [axios with AbortController](https://axios-http.com/docs/cancellation). Previously axios used cancellation token, but now it's deprecated.
+
+`AbortController` can be used with a multiple requests to cancel them at once.
+
+```typescript
+import { useCallback, useRef } from "react";
+import axios from 'axios';
+
+const client = axios.create();
+
+export const useGetUsers = () => {
+  const controller = useRef(new AbortController());
+  
+  const get = useCallback(async () => {
+    const result = await client.get("/", {
+	    // params and props here
+		signal: controller.current.signal,
+    });
+
+    return result.data;
+  }, []);
+
+  const cancel = useCallback(() => {
+    controller.current.abort();
+    
+    // controller should be rewritten or all requests will fail
+    controller.current = new AbortController();
+  }, [controller]);
+
+  return { get, cancel };
+};
+```
--- a/content/Frontend/Vue/Adding
+++ b/content/Frontend/Vue/Adding
@ -0,0 +1,17 @@
+The topic's fully covered in the [official documentation](https://vuejs.org/guide/typescript/options-api.html#augmenting-global-properties) and in [Add global variable to window](Add%20global%20variable%20to%20window.md).
+
+For example, you want to add global `$http` and `$translate` services to all of project's components:
+
+```typescript
+// ~/index.d.ts or ~/custom.d.ts
+
+import axios from 'axios'
+
+declare module 'vue' {
+  interface ComponentCustomProperties {
+    $http: typeof axios
+    $translate: (key: string) => string
+  }
+}
+```
+
--- a/content/Frontend/Vue/Make
+++ b/content/Frontend/Vue/Make
@ -0,0 +1,16 @@
+By default [Nuxt Content Plugin](https://content.nuxtjs.org) not handling `==highlight==` links. To fix that we will create `Nitro` plugin:
+
+```typescript
+// ~/server/plugins/highlight.ts
+export default defineNitroPlugin((nitroApp) => {
+  nitroApp.hooks.hook("content:file:beforeParse", (file) => {
+    if (file._id.endsWith(".md")) {
+      file.body = file.body.replace(
+        /==([^=]+)==/gs,
+        `<span class="highlight">$1</span>`
+      );
+    }
+  });
+});
+```
+
--- a/content/Git/Force
+++ b/content/Git/Force
@ -0,0 +1,8 @@
+Forces #git to use https even if remote url is #SSH. Useful for the networks with blocked #ssh protocol.
+
+Put this inside your `~/.gitconfig`:
+
+```c
+[url "https://github.com"]
+	insteadOf = git://github.com
+```
--- a/content/Git/Git
+++ b/content/Git/Git
@ -0,0 +1,30 @@
+Shorthands for #git commands can be specified. Should be placed at `~/.gitconfig`.
+
+```c
+[alias]
+	flush = git clean-branches branch | grep -v master | xargs git branch -D
+	lol = log --oneline --graph
+	l = lol
+	c = commit -am
+	cv = commit --no-verify -am
+	p = push
+	pf = p --force-with-lease
+	ignore-now = update-index --skip-worktree
+```
+
+| **command**  | **description**   |
+|---|---|
+| `git flush` | drops all branches, except master |
+| `git lol` | shows log |
+|`git c` | commits with message |
+| `git cv` | commits without hooks |
+| `git p` | pushes |
+| `git pf` | push with --force and additional check |
+| `git ignore-now` | starts ignoring file from now on |
+
+
+
+
+
+
+
--- a/content/GraphQL/Apollo
+++ b/content/GraphQL/Apollo
@ -0,0 +1,79 @@
+Say, we have `gql` response like this and we wan't to have pagination with it. Let's merge it as it specified in [official documentation](https://www.apollographql.com/docs/react/caching/cache-field-behavior/#the-merge-function)
+
+```graphql
+query listItems(
+  filter: Filter, 
+  sort: String,
+  limit: Number,
+  offset: Number,
+): ItemList!
+
+input Filter {
+  name: String!
+  type: String!
+}
+
+type ItemList {
+  items: [Item!]!
+  totalCount: Int!
+}
+```
+
+We will setup `ApolloClient` with `typePolicies` to merge incoming data in cache:
+
+```typescript
+import { ApolloClient, InMemoryCache } from '@apollo/client';
+
+const client = new ApolloClient({
+  // ...
+  cache: new InMemoryCache({ typePolicies }),
+  // ...
+});
+
+export const typePolicies: TypePolicies = {
+  Query: {
+    fields: {
+      // query name
+      listItems: {
+        // apollo will serialize and use keyArgs as unique
+        // identifier in cache for every query
+        // consider choosing the right fields, 
+        // i.e. limit and offset won't work here
+        keyArgs: [
+          'sort', // primitive type
+          'filter', ['name', 'type'] // nested fields of `filter`
+        ],
+        merge: mergeItemsWithTotalCount,
+      },
+  }
+}
+```
+
+We will need merge function `mergeItemsWithTotalCount`, which will join results of query and cached data for specific key:
+
+```typescript
+/** merges all sources with { items: unknown[], totalCount: number } */
+const mergeItemsWithTotalCount = (existing, incoming, { args }) => {
+    // no existing data
+    if (!existing || !args?.offset || args.offset < existing.length) {
+      return incoming || [];
+    }
+
+    // If hook was called multiple times
+    if (existing?.items?.length && args?.offset < existing.items.length) {
+      return existing || [];
+    }
+
+    // merge cache and incoming data
+    const items = [...(existing?.items || []), ...(incoming?.items || [])];
+
+    // apply latest result for totalCount
+    const totalCount = incoming?.totalCount || existing?.totalCount;
+
+    return {
+      ...(incoming || existing || {}),
+      items,
+      totalCount,
+    };
+  };
+```
--- a/content/GraphQL/Refresh
+++ b/content/GraphQL/Refresh
@ -0,0 +1,157 @@
+If your GraphQL api needs token refresh option, you can pass custom fetch function for Apollo Client.
+
+```typescript
+export const createApolloClient = (
+  url: string,
+  logout: () => void,
+  getAuthorizationData: () => { authorization: string },
+  refreshToken: () => Promise<
+    { accessToken: string; refreshToken: string } | undefined
+  >,
+) =>
+  new ApolloClientBase({
+    // ...other options
+    link: ApolloLink.from([
+      // ...other options
+      setContext(async (_, { headers }) => {
+        return {
+          headers: {
+            ...headers,
+            ...getAuthorizationData(),
+          },
+        };
+      }),
+      new HttpLink({
+        uri: url,
+        fetch: fetchWithTokenRefresh(logout, refreshToken),
+      }),
+    ]),
+  });
+```
+
+Custom fetch function for this request. You should tune `hasUnauthorizedError` and 
+`isRefreshRequestOptions` to match your api.
+
+```typescript
+/** Global singleton for refreshing promise */
+let refreshingPromise: Promise<string> | null = null;
+
+/** Checks if GraphQl errors has unauthenticated error */
+const hasUnauthorizedError = (errors: Array<{ code?: ErrorCode }>): boolean =>
+  Array.isArray(errors) &&
+  errors.some(error => {
+    return error.status === 401; // Distinguish unauthorized error here
+  });
+
+/** Detects if customFetch is sending refresh request */
+const isRefreshRequestOptions = (options: RequestInit) => {
+  try {
+    const body = JSON.parse(options?.body as string);
+    return body.operationName === 'RefreshToken';
+  } catch (e) {
+    return false;
+  }
+};
+
+/** fetchWithTokenRefresh is a custom fetch function with token refresh for apollo */
+export const fetchWithTokenRefresh =
+  (
+    logout: () => void,
+    refreshToken: () => Promise<
+      { accessToken: string; refreshToken: string } | undefined
+    >,
+  ) =>
+  async (uri: string, options: RequestInit): Promise<Response> => {
+    // already refreshing token, wait for it and then use refreshed token
+    // or use empty authorization if refreshing failed
+    if (
+      !isRefreshRequestOptions(options) &&
+      refreshingPromise &&
+      (options.headers as Record<string, string>)?.authorization
+    ) {
+      const newAccessToken = await refreshingPromise
+        .catch(() => {
+          // refreshing token from other request failed, retry without authorization
+          return '';
+        });
+      
+      options.headers = {
+        ...(options.headers || {}),
+        authorization: newAccessToken,
+      };
+    }
+
+    return fetch(uri, options).then(async response => {
+      const text = await response.text();
+      const json = JSON.parse(text);
+
+      // check for unauthorized errors, if not present, just return result
+      if (
+        isRefreshRequestOptions(options) ||
+        !json?.errors ||
+        !Array.isArray(json.errors) ||
+        !hasUnauthorizedError(json.errors)
+      ) {
+        return {
+          ...response,
+          ok: true,
+          json: async () =>
+            new Promise<unknown>(resolve => {
+              resolve(json);
+            }),
+          text: async () =>
+            new Promise<string>(resolve => {
+              resolve(text);
+            }),
+        };
+      }
+
+      // If unauthorized, refresh token and try again
+      if (!refreshingPromise) {
+        refreshingPromise = refreshToken()
+          .then(async (tokens): Promise<string> => {
+            refreshingPromise = null;
+
+            if (!tokens?.accessToken) {
+              throw new Error('Session expired');
+            }
+
+            return tokens?.accessToken;
+          })
+          .catch(() => {
+            refreshingPromise = null;
+
+            // can't refresh token. logging out
+            logout();
+            throw new Error('Session expired');
+          });
+      }
+
+      // success or any non-auth error
+      return refreshingPromise
+        .then(async (newAccessToken: string) => {
+          // wait for other request's refreshing query to finish, when retry
+
+          return fetch(uri, {
+            ...options,
+            headers: {
+              ...(options.headers || {}),
+              authorization: newAccessToken,
+            },
+          });
+        })
+        .catch(async () => {
+          // refreshing token from other request failed, retry without authorization
+
+          return fetch(uri, {
+            ...options,
+            headers: {
+              ...(options.headers || {}),
+              authorization: '',
+            },
+          });
+        });
+    });
+  };
+
+```
--- a/content/Linux/Gitea
+++ b/content/Linux/Gitea
@ -0,0 +1,29 @@
+Self-hosted #git repositories with [gitea](https://gitea.io/ru-ru/) and #docker.
+
+## Setting up with docker-compose
+
+```yaml
+version: "3"
+
+networks:
+  gitea:
+    external: false
+services:
+  server:
+    image: gitea/gitea:latest
+    container_name: gitea
+    environment:
+      - USER_UID=1000
+      - USER_GID=1000
+    restart: always
+    networks:
+      - gitea
+    volumes:
+      - ./var/lib/gitea:/data
+      - ./etc/gitea:/etc/gitea
+      - /etc/timezone:/etc/timezone:ro
+      - /etc/localtime:/etc/localtime:ro
+    ports:
+      - "3000:3000"
+      - "222:22"
+```
--- a/content/Linux/Google
+++ b/content/Linux/Google
@ -0,0 +1,70 @@
+[Photo Prism](https://photoprism.app/) is a free alternative to Google photos, can be set up with #docker.
+
+## Docker compose file to run it
+
+Check out current [example](https://dl.photoprism.app/docker/docker-compose.yml) at photoprism's [documentation](https://docs.photoprism.app/getting-started/docker-compose/).
+
+```yaml
+version: '3.5'
+
+services:
+  photoprism:
+    container_name: photoprism__app
+    image: photoprism/photoprism:latest
+    depends_on:
+      - mariadb
+    restart: unless-stopped
+    security_opt:
+      - seccomp:unconfined
+      - apparmor:unconfined
+    ports:
+      - 2342:2342 # HTTP port (host:container)
+    environment:
+      PHOTOPRISM_ADMIN_PASSWORD: "password"
+      PHOTOPRISM_SITE_URL: "https://service.url/"
+      PHOTOPRISM_ORIGINALS_LIMIT: 5000
+      PHOTOPRISM_HTTP_COMPRESSION: "gzip"
+      PHOTOPRISM_DEBUG: "false"          
+      PHOTOPRISM_PUBLIC: "false"      
+      PHOTOPRISM_READONLY: "false"    
+      PHOTOPRISM_EXPERIMENTAL: "false"
+      PHOTOPRISM_DISABLE_CHOWN: "false"
+      PHOTOPRISM_DISABLE_WEBDAV: "false" 
+      PHOTOPRISM_DISABLE_SETTINGS: "false"
+      PHOTOPRISM_DISABLE_TENSORFLOW: "false"
+      PHOTOPRISM_DISABLE_FACES: "false"     
+      PHOTOPRISM_DISABLE_CLASSIFICATION: "false"
+      PHOTOPRISM_DARKTABLE_PRESETS: "false"     
+      PHOTOPRISM_DETECT_NSFW: "false"           
+      PHOTOPRISM_UPLOAD_NSFW: "true"            
+      PHOTOPRISM_DATABASE_DRIVER: "mysql"       
+      PHOTOPRISM_DATABASE_SERVER: "mariadb:3306"
+      PHOTOPRISM_DATABASE_NAME: "photoprism"    
+      PHOTOPRISM_DATABASE_USER: "root"         
+      PHOTOPRISM_DATABASE_PASSWORD: "insecure" 
+      PHOTOPRISM_SITE_TITLE: "PhotoPrism"
+      PHOTOPRISM_SITE_CAPTION: "Browse Your Life"
+      PHOTOPRISM_SITE_DESCRIPTION: ""
+      PHOTOPRISM_SITE_AUTHOR: ""
+      HOME: "/photoprism"
+    working_dir: "/photoprism"
+    volumes:
+      - "./data/originals:/photoprism/originals"    
+      - "./data/imports:/photoprism/import"
+      - "./data/storage:/photoprism/storage"
+  mariadb:
+    container_name: photoprism__db
+    restart: unless-stopped
+    image: mariadb:10.6
+    security_opt:
+      - seccomp:unconfined
+      - apparmor:unconfined
+    command: mysqld --innodb-buffer-pool-size=128M --transaction-isolation=READ-COMMITTED --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci --max-connections=512 --innodb-rollback-on-timeout=OFF --innodb-lock-wait-timeout=120
+    volumes:
+      - "./database:/var/lib/mysql" # Important, don't remove
+    environment:
+      MYSQL_ROOT_PASSWORD: insecure
+      MYSQL_DATABASE: photoprism
+      MYSQL_USER: photoprism
+      MYSQL_PASSWORD: insecure
+```
--- a/content/Linux/Resume
+++ b/content/Linux/Resume
@ -0,0 +1,5 @@
+Running this script will enter currently running `screen` session or will start new one.
+
+```shell
+( screen -r bash || ( screen -d bash && screen -r bash || screen -SAm bash bash ) )
+```
--- a/content/Linux/Rsync
+++ b/content/Linux/Rsync
@ -0,0 +1,16 @@
+Downloads file from #SSH with rsync and puts it in current folder.
+
+```bash
+#!/bin/bash
+
+PORT=22
+USER=user
+HOST=example.com
+REMOTE_PATH=/tmp
+REMOTE_FILE=sample.text
+DEST_PATH=./
+
+rsync -a -e "ssh -p $PORT" -P -v \
+	"$USER@$HOST:$REMOTE_PATH/$REMOTE_FILE" \
+	"$DEST_PATH"
+```
--- a/content/Linux/SSH.md
+++ b/content/Linux/SSH.md
@ -0,0 +1,13 @@
+## Config aliases for #SSH hosts
+
+#SSH config can be used to made aliases for different hosts. Should be put at `~/.ssh/config`. To simply call `ssh router` without parameters, use this:
+
+```
+Host router
+	HostName 192.168.0.1
+	IdentityFile ~/.ssh/id_rsa
+	User root
+	Port 22522
+```
+
+
--- a/content/Linux/Setting
+++ b/content/Linux/Setting
@ -0,0 +1,57 @@
+## Fallback url for SPA-s
+
+```nginx
+server {
+  # ...
+  location / {
+    # First attempt to serve request as file, then
+    # as directory, then fall back to displaying a 404.
+    try_files $uri $uri/ =404;
+  }
+  # ...
+}
+```
+
+## Set up for uploads
+
+```nginx
+server {
+  # ...
+  client_max_body_size 200M;
+  # ...
+}
+```
+
+## Reverse proxy for https 
+
+Given config forwards `https` traffic to `http` on port `8080` for https://next.vault48.org
+ with http2 support if possible.
+ 
+```nginx
+server {
+  listen 80;
+  server_name next.vault48.org;
+  return 301 https://next.vault48.org$request_uri;
+}
+
+server {
+  listen 443 ssl http2;
+  listen [::]:443 ssl http2;
+  
+  # managed by Certbot
+  ssl_certificate /etc/letsencrypt/live/vault48.org/fullchain.pem; 
+  ssl_certificate_key /etc/letsencrypt/live/vault48.org/privkey.pem; 
+  ssl_trusted_certificate /etc/letsencrypt/live/vault48.org/chain.pem;
+  
+  server_name next.vault48.org;
+  
+  location / {
+    proxy_redirect off;
+    proxy_set_header Host $host;
+    proxy_set_header X-Real-IP $remote_addr;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    
+    proxy_pass http://127.0.0.1:8080;
+  }
+}
+```
--- a/content/SQL/MySQL
+++ b/content/SQL/MySQL
@ -0,0 +1,37 @@
+## Install MariaDB on Ubuntu 20.04 LTS
+
+```bash
+sudo apt update
+sudo apt install mariadb-server
+sudo mysql_secure_installation
+```
+
+## Access Database from outside
+
+Open `/etc/mysql/mariadb.conf.d/50-server.cnf` and change the `bind-address` to:
+
+```nginx
+...
+bind-address = 0.0.0.0
+...
+```
+
+## Create Administrative User
+
+1. Create a new user `newuser` for the host `localhost` with a new `password`:
+
+```mysql
+CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'password';
+```
+
+2. Grant all permissions to the new user
+
+```mysql
+GRANT ALL PRIVILEGES ON * . * TO 'newuser'@'localhost';
+``` 
+
+3. Update permissions
+
+```mysql
+FLUSH PRIVILEGES;
+```
--- a/content/SQL/Postgress
+++ b/content/SQL/Postgress
@ -0,0 +1,105 @@
+## Install PostgreSQL 12 on Ubuntu 20.04 LTS
+
+```bash
+sudo apt update
+sudo apt install -y postgresql postgresql-contrib postgresql-client
+sudo systemctl status postgresql.service
+```
+
+## Initial database connection
+
+A local connection (from the database server) can be done by the following command:
+
+```bash
+sudo -u postgres psql
+
+psql (12.12 (Ubuntu 12.12-0ubuntu0.20.04.1))
+Type "help" for help.
+
+postgres=#
+```
+
+## Set password for postgres database user
+
+The password for the `postgres` database user can be set the the quick command `\password`
+or by `alter user postgres password 'Supersecret'`. A connection using the `postgres` user
+is still not possible from the "outside" hence to the default settings in the `pg_hba.conf`.
+
+### Update pg_hba.conf to allow postgres user connections with password
+
+In order to allow connections of the `postgres` database user not using OS user
+authentication, you have to update the `pg_hba.conf` which can be found under
+`/etc/postgresql/12/main/pg_hba.conf`.
+
+```shell
+sudo vi /etc/postgresql/12/main/pg_hba.conf
+
+...
+local   all             postgres                                peer
+...
+```
+
+Change the last section of the above line to `md5`.
+
+```
+local   all             postgres                                md5
+```
+
+A restart is required in order to apply the new configuration:
+
+```bash
+sudo systemctl restart postgresql
+```
+
+Now a connection from outside the database host is possible e.g.
+
+```bash
+psql -U postgres -d postgres -h databasehostname
+```
+
+## Creation of additional database users
+
+A database user can be created by the following command:
+
+```sql
+create user myuser with encrypted password 'Supersecret';
+CREATE ROLE
+
+postgres=# \du
+                                   List of roles
+ Role name |                         Attributes                         | Member of
+-----------+------------------------------------------------------------+-----------
+ myuser    |                                                            | {}
+ postgres  | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
+```
+
+## Creation of additional databases
+
+One can create new Postgres databases within an instance. Therefore you can use the `psql`
+command to login (see above).
+
+```sql
+CREATE DATABASE dbname OWNER myuser;
+CREATE DATABASE
+
+postgres=# \l
+                                  List of databases
+   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges
+-----------+----------+----------+-------------+-------------+-----------------------
+ dbname    | myuser   | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
+ postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
+ template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
+           |          |          |             |             | postgres=CTc/postgres
+ template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
+           |          |          |             |             | postgres=CTc/postgres
+```
+
+You can leave the `OWNER` section of the command, when doing so, the current user will become
+owner of the newly created database.
+
+To change the owner of an existing database later, you can use the following command:
+
+```sql
+postgres=# alter database dbname owner to myuser;
+ALTER DATABASE
+```
--- a/content/Typescript/Add
+++ b/content/Typescript/Add
@ -0,0 +1,50 @@
+Sometimes you want to add global variable to your `window`. That thing's called [global module augmentation](https://www.typescriptlang.org/docs/handbook/declaration-merging.html#global-augmentation).
+
+Say you need to call `window.doFancyThings()`. For that you should augment global `window` interface in `*.d.ts` file:
+
+```typescript
+declare global {
+  interface Window {
+    doFancyThings: () => void;
+  }
+}
+```
+
+This is useful for declaring global `window.ethereum` (or `window.web3`) in [blockchain](/blockchain/Common%20typescript%20examples) projects with typescript, which use wallet browser extensions. 
+
+## Augmenting existing interface
+
+For example, you have class `Sample` without any functionality:
+
+```typescript
+// Sample.ts
+
+export class Sample {
+  // nothing :-)
+}
+```
+
+Then you want extend it with `doFancyThings()` method. That can be achieved with said [module augmentation](https://www.typescriptlang.org/docs/handbook/declaration-merging.html#module-augmentation):
+
+```typescript
+// fancyThings.ts
+import { Sample } from "./Sample";
+
+declare module "./Sample" {
+  interface Sample {
+    doFancyThings: () => void;
+  }
+}
+```
+
+Now you can call `sample.doFancyThings()` by importing both `.ts` files:
+
+```typescript
+import { Sample } from "./sample";
+import "./fancyThings";
+
+const sample = new Sample();
+sample.doFancyThings(); // ok
+```
+
+This example is useful for [adding global properties to component](../Frontend/Vue/Adding%20global%20properties%20to%20component.md) in vue.js.
--- a/content/Typescript/Flatten
+++ b/content/Typescript/Flatten
@ -0,0 +1,38 @@
+This helper generates Typescript types for i18n dictionary json
+files by flattening it with period delimiter. Supports plural forms.
+
+Used for typing [i18n.js](https://www.npmjs.com/package/i18n-js) dictionaries;
+
+```typescript
+import en from './en.json';
+type TranslationPath = Flatten<typeof en>;
+
+const t = (key: TranslationPath, options?: TranslateOptions) =>
+    I18nLib.t(key, options);
+```
+
+Flatten type defined here:
+
+```typescript
+// This one based on answer from StackOverflow:
+// https://stackoverflow.com/questions/58434389/typescript-deep-keyof-of-a-nested-object
+
+export type Flatten<T, D extends number = 5> = [D] extends [never]
+  ? never
+  : T extends PluralForm // plural object
+  ? ''
+  : T extends object
+  ? { [K in keyof T]-?: Join<K, Flatten<T[K], Prev[D]>> }[keyof T]
+  : '';
+
+// Fix it for you plural form
+type PluralForm = Record<'one' | 'few' | 'many', string>;
+
+type Join<K, P> = K extends string | number
+  ? P extends string | number
+    ? `${K}${'' extends P ? '' : '.'}${P}`
+    : never
+  : never;
+
+type Prev = [never, 0, 1, 2, 3, 4, 5, ...Array<0>];
+```
--- a/content/Typescript/Type
+++ b/content/Typescript/Type
@ -0,0 +1,20 @@
+Useful for type checking at compile and run time:
+
+```typescript
+function isFish(pet: Fish | Bird): pet is Fish {
+  return (pet as Fish).swim !== undefined;
+}
+```
+
+Usage:
+
+```typescript
+const pet = getSmallPet();
+ 
+if (isFish(pet)) {
+  pet.swim();
+} else {
+  pet.fly();
+}
+```
+