kysely-typegen/src/index.ts

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

export type TableMetadata = KyselyTableMetadata
export type ColumnMetadata = TableMetadata["columns"][number]
export interface EnumMetadata {
  name: string
  values: string[]
}

export interface IntrospectedEnums {
  named: EnumMetadata[]
  inline: Map<string, string[]>
}

const PREAMBLE_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",
  "",
]

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

  public constructor(input: { database: Kysely<any> }) {
    this.database = input.database
  }

  public async getTables(): Promise<TableMetadata[]> {
    const tables = await this.database.introspection.getTables()
    return tables.sort((a, b) => {
      return a.name.localeCompare(b.name)
    })
  }

  protected normalizeDataType(dataType: string): string {
    return dataType
  }

  protected resolveColumnType(
    table: TableMetadata,
    column: ColumnMetadata,
    scalars: Record<string, string>,
    inlineEnums: Map<string, string>,
  ): string {
    const inlineUnion = inlineEnums.get(`${table.name}.${column.name}`)
    if (inlineUnion != null) {
      return inlineUnion
    }
    const dataType = this.normalizeDataType(column.dataType)
    return scalars[dataType] ?? "unknown"
  }

  protected formatColumnComment(comment: string): string[] {
    const trimmedComment = comment.trim()
    if (trimmedComment.length === 0) {
      return []
    }
    const lines = trimmedComment.replaceAll("*/", "*\\/").split(/\r?\n/u)
    if (lines.length === 1) {
      return [`  /** ${lines[0]} */`]
    }
    return [
      "  /**",
      ...lines.map((line) => {
        return line.length === 0 ? "   *" : `   * ${line}`
      }),
      "   */",
    ]
  }

  public getTablesTypegen(
    tables: TableMetadata[],
    enums: EnumMetadata[],
    inlineEnums: Map<string, string>,
  ): string[] {
    const scalars: Record<string, string> = { ...this.scalars }
    for (const enumMetadata of enums) {
      scalars[enumMetadata.name] = enumMetadata.name
    }
    const result: string[] = []
    for (const table of tables) {
      result.push(`export interface ${table.name} {`)
      const columns = [...table.columns].sort((a, b) => {
        return a.name.localeCompare(b.name)
      })
      for (const column of columns) {
        const baseType = this.resolveColumnType(table, column, scalars, inlineEnums)
        let columnType = column.isNullable ? `${baseType} | null` : baseType
        if (column.hasDefaultValue || column.isAutoIncrementing) {
          columnType = `Generated<${columnType}>`
        }
        if (column.comment != null) {
          result.push(...this.formatColumnComment(column.comment))
        }
        result.push(`  ${column.name}: ${columnType}`)
      }
      result.push("}", "")
    }
    return result
  }

  protected async introspectEnums(): Promise<IntrospectedEnums> {
    return { named: [], inline: new Map() }
  }

  public async getEnums(): Promise<{ enums: EnumMetadata[]; inlineEnums: Map<string, string> }> {
    const { named, inline } = await this.introspectEnums()
    const enums = [...named].sort((a, b) => {
      return a.name.localeCompare(b.name)
    })
    const inlineEnums = new Map<string, string>()
    for (const [key, values] of inline) {
      inlineEnums.set(key, this.formatEnumUnion(values))
    }
    return { enums, inlineEnums }
  }

  protected formatEnumUnion(values: string[]): string {
    return [...values]
      .sort((a, b) => {
        return a.localeCompare(b)
      })
      .map((value) => {
        return `"${value}"`
      })
      .join(" | ")
  }

  public getEnumsTypegen(enums: EnumMetadata[]): string[] {
    const result: string[] = []
    for (const enumMetadata of enums) {
      result.push(
        `export type ${enumMetadata.name} = ${this.formatEnumUnion(enumMetadata.values)}`,
        "",
      )
    }
    return result
  }

  public async typegen(): Promise<{
    lines: string[]
    enums: EnumMetadata[]
    inlineEnums: Map<string, string>
    tables: TableMetadata[]
  }> {
    const [tables, { enums, inlineEnums }] = await Promise.all([this.getTables(), this.getEnums()])
    const lines: string[] = [
      ...PREAMBLE_LINES,
      ...this.getEnumsTypegen(enums),
      ...this.getTablesTypegen(tables, enums, inlineEnums),
      "export interface DB {",
      ...tables.map((table) => {
        return `  ${table.name}: ${table.name}`
      }),
      "}",
    ]
    return { lines, enums, inlineEnums, tables }
  }
}