import { unixNow } from "applesauce-core/helpers";
import { Database } from "better-sqlite3";

type ScriptFunction = (database: Database, log: (message: string) => void) => Promise<void>;
type MigrationScript = { version: number; migrate: ScriptFunction };

export class MigrationSet {
  scripts: MigrationScript[] = [];

  name: string;
  database?: Database;
  setupMigrationTables = true;

  constructor(name: string, database?: Database) {
    this.database = database;
    this.name = name;
  }

  private ensureMigrations(database: Database | undefined = this.database) {
    if (!database) throw new Error("database required");

    database
      .prepare(
        `
			CREATE TABLE IF NOT EXISTS "migrations" (
				"id"	INTEGER NOT NULL,
				"name"	TEXT NOT NULL,
				"version"	INTEGER NOT NULL,
				"date"	INTEGER NOT NULL,
				PRIMARY KEY("id" AUTOINCREMENT)
			);
			`,
      )
      .run();
    database
      .prepare(
        `
			CREATE TABLE IF NOT EXISTS "migration_logs" (
				"id"	INTEGER NOT NULL,
				"migration"	INTEGER NOT NULL,
				"message"	TEXT NOT NULL,
				FOREIGN KEY("migration") REFERENCES "migrations",
				PRIMARY KEY("id" AUTOINCREMENT)
			);
			`,
      )
      .run();
  }

  addScript(version: number, migrate: ScriptFunction) {
    this.scripts.push({ version, migrate });
  }

  async run(database: Database | undefined = this.database) {
    if (!database) throw new Error("database required");

    // ensure migration tables are setup
    await this.ensureMigrations(database);

    const prev = database
      .prepare<[string], { name: string; version: number }>(`SELECT * FROM migrations WHERE name=?`)
      .all(this.name);
    const lastVersion = prev.reduce((v, m) => Math.max(m.version, v), 0);

    const sorted = Array.from(this.scripts).sort((a, b) => a.version - b.version);

    let version = lastVersion;
    for (const script of sorted) {
      if (version < script.version) {
        let logs: string[] = [];
        await database.transaction(() => {
          return script.migrate(database, (message) => logs.push(message));
        })();

        version = script.version;

        // save the migration
        database.transaction(() => {
          const result = database
            .prepare<[string, number, number]>(`INSERT INTO migrations (name, version, date) VALUES (?, ?, ?)`)
            .run(this.name, script.version, unixNow());

          const insertLog = database.prepare<[number | bigint, string]>(
            `INSERT INTO migration_logs (migration, message) VALUES (?, ?)`,
          );

          for (const message of logs) {
            insertLog.run(result.lastInsertRowid, message);
          }
        })();
      }
    }
  }
}