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import type { Adapter } from "../adapters/adapter.ts";import { Colors, joinPath } from "../../deps.ts";import { Schema } from "./schema.ts";import { createMigrationTimestamp } from "../utils/date.ts";
export interface Migration {  up(schema: Schema): Promise<void>;  down(schema: Schema): Promise<void>;}
interface MigrationInfo {  migration: Migration;  name: string;  isExecuted: boolean;  batch: number;}
/** * Run migration classes */export class MigrationRunner {  constructor(    /** Migration files directory */    private migrationDir: string,    /** The database adapter to perform queries */    private adapter: Adapter,    /** The version of currently used Cotton */    private version: string,  ) {}
  /**   * Create a new migration script   *    * @param name the name of the migration   */  public async createMigrationFile(name: string): Promise<string> {    if (!name.match(/^[A-Za-z]+$/)) {      throw new Error(        `Invalid name for migration '${name}', name can only contain letters!`,      );    }
    // Create the migrations folder if not exists    await this.ensureMigrationDir();
    // Create a unique timestamps    const timestamp = createMigrationTimestamp();
    // Generate the file name    const fileName = `${this.migrationDir}/${timestamp + "_" + name}.ts`;
    // Write the file    await Deno.writeTextFile(      fileName,      `import { Schema } from "https://deno.land/x/cotton@${this.version}/mod.ts";\n\nexport async function up(schema: Schema) {\n  // Do something...\n}\n\nexport async function down(schema: Schema) {\n  // Do something...\n}\n`,    );
    console.log(`${Colors.green("Created:")} ${fileName}`);
    return fileName;  }
  /**   * Get all migration classes   */  private async getAllMigrationFiles(): Promise<MigrationInfo[]> {    const migrations: MigrationInfo[] = [];
    // Loop through all files    for await (const file of Deno.readDir(this.migrationDir)) {      if (file.isFile) {        let migration: Migration;
        try {          const fileContent = await import(            "file://" + joinPath(this.migrationDir, file.name)          );
          if (            typeof fileContent.up !== "function" ||            typeof fileContent.down !== "function"          ) {            throw new Error();          }
          migration = { up: fileContent.up, down: fileContent.down };        } catch {          throw new Error(`Failed to load '${file.name}' migration file!`);        }
        migrations.push({          migration,          name: file.name.split(".")[0],          batch: 0,          isExecuted: false,        });      }    }
    return migrations.sort((a, b) => (a.name > b.name) ? 1 : -1);  }
  /**   * Get all available migrations   */  public async getAllMigrations(): Promise<{    migrations: MigrationInfo[];    lastBatch: number;  }> {    await this.createMigrationsTable();
    const migrations = await this.adapter      .table("migrations")      .select("name", "batch")      .execute();    const migrationFiles = await this.getAllMigrationFiles();
    for (const migration of migrations) {      const migrationIndex = migrationFiles.findIndex((item) =>        item.name === migration.name      );      if (migrationIndex === -1) {        throw new Error(`Migration '${migration.name}' is missing!`);      }
      migrationFiles[migrationIndex].isExecuted = true;      migrationFiles[migrationIndex].batch = migration.batch as number;    }
    const lastBatch = migrationFiles.reduce((prev, current) =>      (prev.batch > current.batch) ? prev : current    );
    return {      migrations: migrationFiles,      lastBatch: lastBatch.batch,    };  }
  /**   * Execute a new batch of migrations   */  public async applyMigrations() {    const { migrations, lastBatch } = await this.getAllMigrations();
    for (const migration of migrations) {      if (!migration.isExecuted) {        try {          console.log(`${Colors.yellow("Migrating:")} ${migration.name}`);          await migration.migration.up(new Schema(this.adapter));          await this.adapter            .table("migrations")            .insert({ name: migration.name, batch: lastBatch + 1 })            .execute();          console.log(`${Colors.green("Migrated:")}  ${migration.name}`);        } catch {          throw new Error(`Failed to apply migration '${migration.name}'!`);        }      }    }  }
  /**   * Revert executed migrations from the last batch   *    * @param steps the number of migrations you want to revert   */  public async revertMigrations(steps?: number) {    let { migrations, lastBatch } = await this.getAllMigrations();
    if (typeof steps === "number" && migrations.length) {      migrations = migrations.slice(Math.max(migrations.length - steps, 0));    } else if (lastBatch > 0) {      migrations = migrations.filter((migration) =>        migration.batch === lastBatch      );    } else {      throw new Error("No migration to revert!");    }
    for (const migration of migrations) {      try {        console.log(`${Colors.yellow("Reverting:")} ${migration.name}`);        await migration.migration.down(new Schema(this.adapter));        await this.adapter          .table("migrations")          .where("name", migration.name)          .delete()          .execute();        console.log(`${Colors.green("Reverted:")}  ${migration.name}`);      } catch {        throw new Error(`Failed to revert migration '${migration.name}'!`);      }    }  }
  /**   * Create the `migrations` table if it doesn't exist yet   */  public async createMigrationsTable() {    const schema = new Schema(this.adapter);    if (!await schema.hasTable("migrations")) {      await schema.createTable("migrations", (table) => {        table.id();        table.varchar("name", 255).unique().notNull();        table.integer("batch").notNull();      });      console.log(`${Colors.green("Migration table created successfully!")}`);    }  }  /**   * Ensures that the migration directory exists.   * If the directory structure does not exist, it is created. Like mkdir -p.   * Requires the `--allow-read` and `--allow-write` flag.   */  public async ensureMigrationDir(): Promise<void> {    try {      const fileInfo = await Deno.lstat(this.migrationDir);      if (!fileInfo.isDirectory) throw null;    } catch (err) {      if (err instanceof Deno.errors.NotFound || err === null) {        // if dir not exists. then create it.        await Deno.mkdir(this.migrationDir, { recursive: true });        return;      }
      throw err;    }  }}