feature: extend readme with docs and meta info (#4)

add installation, usage, todos, support, contributors, and license sections to readme

Author: yss14

README.md

@@ -1,2 +1,175 @@
 # postgres-schema-builder
-Simple postgres schema builder leveraging Typescript's type system to enable typesafe queries
+Simple postgres schema builder for Node.JS leveraging Typescript's type system to enable typesafe queries
+
+[![Build Status](https://travis-ci.com/yss14/postgres-schema-builder.svg?branch=master)](https://travis-ci.com/yss14/postgres-schema-builder)
+[![Dependabot Status](https://api.dependabot.com/badges/status?host=github&repo=yss14/postgres-schema-builder)](https://dependabot.com)
+
+## Installation
+`npm i postgres-schema-builder` or `yarn add postgres-schema-builder`
+
+## Usage
+
+If you need a reference project which uses `postgres-schema-builder`, have a look at [musicshare](https://github.com/yss14/musicshare/tree/master/projects/backend/src/database).
+
+### Schema definition
+
+The recommended way to define your database schema is to export a namespace indicating the schema version. The namespace itself contains the table definitions.
+
+```typescript
+// DatabaseV1.ts
+import { TableSchema, ColumnType, NativeFunction, ForeignKeyUpdateDeleteRule, JSONType } from "postgres-schema-builder"
+
+export namespace DatabaseV1 {
+    const baseSchema = TableSchema({
+		date_added: { type: ColumnType.TimestampTZ, nullable: false, defaultValue: { func: NativeFunction.Now } },
+		date_removed: { type: ColumnType.TimestampTZ, nullable: true },
+	})
+
+	export const users = TableSchema({
+		...baseSchema,
+		user_id: { type: ColumnType.Integer, primaryKey: true, unique: true },
+        name: { type: ColumnType.Varchar, nullable: false },
+        settings: { type: JSONType<ISomeSettingsInterface>(), nullable: false },
+    })
+
+    export const user_emails = TableSchema({
+        user_id_ref: {type: ColumnType.Integer, primaryKey: true, nullable: false, foreignKeys: [{ targetTable: 'users', targetColumn: 'user_id', onDelete: ForeignKeyUpdateDeleteRule.Cascade }]},
+        email: { type: ColumnType.Varchar, primaryKey: true, nullable: false },
+    })
+    
+    // ...more tables
+}
+```
+
+All available `ColumnType`s can be found in the (`table.ts file`)[https://github.com/yss14/postgres-schema-builder/blob/master/src/table.ts#L78].
+
+### Interfaces and Table API
+
+After defining the tables of our schema, we can create and export an interface for each table, which contains each column as `key`, as well as the respective TypeScript type infered from the column's `ColumnType`.
+
+Furthermore, we can also create a table object for each table entry of our schema, which provides useful API methods for typesafe queries.
+
+```typescript
+// tables.ts
+import { TableRecord, Table } from "postgres-schema-builder"
+import { DatabaseV1 } from "./DatabaseV1"
+
+export const Tables = DatabaseV1
+
+export interface IUserDBResult extends TableRecord<typeof Tables.users> { }
+export interface IUserEMailDBResult extends TableRecord<typeof Tables.user_emails> { }
+// ...more interfaces, for each table one interface
+
+export const UsersTable = Table(Tables, 'users')
+export const UserEMailsTable = Table(Tables, 'user_emails')
+// ...more table objects, for each table one object
+```
+
+### Queries
+
+Now, we can use our exported table objects to create typesafe queries.
+
+```typescript
+import { SQL } from "postgres-schema-builder"
+import { UsersTable, UserEMailsTable} from "./tables.ts"
+
+UsersTable.create() // table create statement
+UsersTable.drop() // table drop statement
+
+UsersTable.insert(['name'])(['Fresh Herrmann']) // insert new entry
+UsersTable.insert(['name'])([null]) // compiler error, since name is not nullable
+UsersTable.insertFromObj({
+	name: 'Fresh Herrmann',
+	date_added: new Date(),
+	settings: {a: 42, b: 'no'},
+})
+
+UsersTable.select('*', ['user_id'])([42]) // select all columns where user_id=42
+UsersTable.select(['user_id', 'name'], ['name'])(['Fresh Herrmann']) // select only user_id and name where name='Fresh Herrmann'
+
+UsersTable.selectAll('*') // select all entries from users
+UsersTable.selectAll(['name']) // select all names from users
+
+UsersTable.update(['name'], ['user_id'])(['Freshly Fresh Herrmann'], [42]) // update entry's name where user_id=42
+
+UsersTable.delete(['user_id'])([1]) // delete where user_id=1
+UsersTable.delete(['user_id'])(['abcd']) // compiler error, since user_id has type number
+
+// create custom query using a join
+const query = SQL.raw<typeof Tables.users & typeof Tables.user_emails>(`
+	SELECT *
+	FROM ${UsersTable.name} u
+	INNER JOIN ${UserEMailsTable.name} e ON u.user_id = e.user_id_ref
+	WHERE u.date_removed IS NULL
+		AND u.user_id = $1;
+`, [42])
+```
+
+### Database Client
+
+`postgres-schema-builder` also provides a small database client to perform our typesafe and custom queries.
+
+```typescript
+import { DatabaseClient } from "postgres-schema-builder"
+import { Pool } from "pg"
+import { UsersTable, Tables} from "./tables.ts"
+import { config } from "./some-config.ts"
+
+const database = DatabaseClient(
+	new Pool({
+		host: config.database.host,
+		port: config.database.port,
+		user: config.database.user,
+		password: config.database.password,
+		database: config.database.database,
+	})
+);
+
+// single query statements
+await database.query(
+    UsersTable.create()
+)
+await database.query(
+    UsersTable.insertFromObj({
+        name: 'Fresh Herrmann',
+        date_added: new Date(),
+        settings: { a: 42, b: 'no' },
+    })
+)
+const dbResults = await database.query(UsersTable.selectAll('*'))
+
+// batch queries
+const insertStatements = someDataArray.map(entry => UsersTable.insertFromObj(entry))
+
+await database.batch(insertStatements)
+
+// leverage transaction creating your database schema
+const createTableStatements = composeCreateTableStatements(Tables) // performs a topological sort on your tables defined in <Tables>
+
+await database.transaction(async (client) => {
+	createTableStatements.forEach(createTableStatement => client.query({ sql: createTableStatement }))
+});
+```
+
+## Todos
+
+* Improve and extend docs
+* Allow `insert` and `insertFromObj` returning the inserted data
+* Enable client to perform multiple queries
+* Introduce database management object enabling schema versioning with migrations
+* Extend test cases and improve code coverage
+
+## Support
+
+### Node.js
+Currently, this package is automatically tested under Node.js versions `8 - 13`.
+All build artifact are compiled to ES6.
+
+### PostgreSQL
+Tested under `v9.6`, might work for newer versions as well.
+
+## Contributors
+* Yannick Stachelscheid ([@yss14](https://github.com/yss14))
+
+## License
+This project is licensed under the [MIT](LICENSE) license.