kysely-typegen/src/index.ts

import type { Kysely, TableMetadata as KyselyTableMetadata } from "kysely"

export type TableMetadata = KyselyTableMetadata
export interface EnumMetadata {
  name: string
  values: string[]
}

export abstract class KyselyTypegenDialect {
  public abstract readonly database: Kysely<any>
  public abstract readonly scalars: Record<string, string>

  public async getTables(): Promise<TableMetadata[]> {
    const tables = await this.database.introspection.getTables()
    return tables.sort((a, b) => {
      return a.name.localeCompare(b.name)
    })
  }
  public getTablesTypegen(tables: TableMetadata[], enums: EnumMetadata[]): string[] {
    const enumNames = new Set(
      enums.map((enumMetadata) => {
        return enumMetadata.name
      }),
    )
    const result: string[] = []
    for (const table of tables) {
      const interfaceName = table.name
      result.push(`export interface ${interfaceName} {`)
      const columns = [...table.columns].sort((a, b) => {
        return a.name.localeCompare(b.name)
      })
      for (const column of columns) {
        const isEnum = enumNames.has(column.dataType)
        const baseType = isEnum ? column.dataType : (this.scalars[column.dataType] ?? "unknown")
        let columnType = column.isNullable ? `${baseType} | null` : baseType
        if (column.hasDefaultValue || column.isAutoIncrementing) {
          columnType = `Generated<${columnType}>`
        }
        result.push(`  ${column.name}: ${columnType}`)
      }
      result.push("}", "")
    }
    return result
  }

  protected abstract getEnumsMap(): Promise<Map<string, string[]>>
  public async getEnums(): Promise<EnumMetadata[]> {
    const enumsMap = await this.getEnumsMap()
    const enums: EnumMetadata[] = []
    for (const [name, values] of enumsMap) {
      enums.push({ name, values })
    }
    return enums.sort((a, b) => {
      return a.name.localeCompare(b.name)
    })
  }
  public getEnumsTypegen(enums: EnumMetadata[]): string[] {
    const result: string[] = []
    for (const enumMetadata of enums) {
      const enumName = enumMetadata.name
      result.push(
        `export type ${enumName} = ${enumMetadata.values
          .map((value) => {
            return `"${value}"`
          })
          .join(" | ")}`,
        "",
      )
    }
    return result
  }

  public abstract typegen(): Promise<{
    lines: string[]
    enums: EnumMetadata[]
    tables: TableMetadata[]
  }>
}
export class KyselyTypegenPostgresDialect extends KyselyTypegenDialect {
  public database: KyselyTypegenDialect["database"]

  // These types have been found through experimentation in Adminer and in the 'pg' source code.
  public readonly scalars: Record<string, string> = {
    bit: "string",
    bool: "boolean",
    box: "string",
    bpchar: "string",
    bytea: "Buffer",
    cidr: "string",
    date: "Timestamp",
    float4: "number",
    float8: "number",
    inet: "string",
    int2: "number",
    int4: "number",
    int8: "Int8",
    json: "Json",
    jsonb: "Json",
    line: "string",
    lseg: "string",
    macaddr: "string",
    money: "string",
    numeric: "Numeric",
    oid: "number",
    path: "string",
    polygon: "string",
    text: "string",
    time: "string",
    timestamp: "Timestamp",
    timestamptz: "Timestamp",
    timetz: "string",
    tsquery: "string",
    tsvector: "string",
    uuid: "string",
    varbit: "string",
    varchar: "string",
    xml: "string",
  }

  public constructor(input: { database: KyselyTypegenDialect["database"] }) {
    super()
    this.database = input.database
  }

  protected async getEnumsMap(): Promise<Map<string, string[]>> {
    const rows = await this.database
      .withoutPlugins()
      .selectFrom("pg_type as type")
      .innerJoin("pg_enum as enum", "type.oid", "enum.enumtypid")
      .innerJoin("pg_catalog.pg_namespace as namespace", "namespace.oid", "type.typnamespace")
      .select(["type.typname as enumName", "enum.enumlabel as enumValue"])
      .execute()
    const enums = new Map<string, string[]>()
    for (const row of rows) {
      const data = row as { enumName: string; enumValue: string }
      enums.set(
        data.enumName,
        [...(enums.get(data.enumName) ?? []), data.enumValue].sort((a, b) => {
          return a.localeCompare(b)
        }),
      )
    }
    return enums
  }

  /**
   * Generate TypeScript types based on the database schema, including tables and enums.
   */
  public async typegen(): Promise<{
    lines: string[]
    enums: EnumMetadata[]
    tables: TableMetadata[]
  }> {
    const [tables, enums] = await Promise.all([this.getTables(), this.getEnums()])
    const lines: string[] = [
      `// This file was automatically generated by \`kysely-typegen\`.`,
      "// Do not edit this file manually.",
      "",
      'import type { ColumnType } from "kysely"',
      "",
      "export type Generated<T> = T extends ColumnType<infer S, infer I, infer U> ? ColumnType<S, I | undefined, U> : ColumnType<T, T | undefined, T>",
      "",
      "export type Timestamp = ColumnType<Date, Date | string, Date | string>",
      "",
      "export type Numeric = ColumnType<string, number | string, number | string>",
      "",
      "export type Int8 = ColumnType<string, bigint | number | string, bigint | number | string>",
      "",
      "export type Json = JsonValue",
      "",
      "export type JsonArray = JsonValue[]",
      "",
      "export interface JsonObject {",
      "  [x: string]: JsonValue | undefined",
      "}",
      "",
      "export type JsonPrimitive = boolean | number | string | null",
      "",
      "export type JsonValue = JsonArray | JsonObject | JsonPrimitive",
      "",
    ]
    lines.push(...this.getEnumsTypegen(enums))
    lines.push(...this.getTablesTypegen(tables, enums))
    lines.push("export interface DB {")
    for (const table of tables) {
      lines.push(`  ${table.name}: ${table.name}`)
    }
    lines.push("}")
    return { lines, enums, tables }
  }
}