import type * as typeFest from 'type-fest'
import type {UmzugStorage} from './storage'

/**
 * Create a type that has mutually exclusive keys.
 * Wrapper for @see `import('type-fest').MergeExclusive` that works for three types
 */
export type MergeExclusive<A, B, C> = typeFest.MergeExclusive<A, typeFest.MergeExclusive<B, C>>

export type Promisable<T> = T | PromiseLike<T>

export type LogFn = (message: Record<string, unknown>) => void

/** Constructor options for the Umzug class */
export type UmzugOptions<Ctx extends {} = Record<string, unknown>> = {
  /** The migrations that the Umzug instance should perform */
  migrations: InputMigrations<Ctx>
  /** A logging function. Pass `console` to use stdout, or pass in your own logger. Pass `undefined` explicitly to disable logging. */
  logger: Record<'info' | 'warn' | 'error' | 'debug', LogFn> | undefined
  /** The storage implementation. By default, `JSONStorage` will be used */
  storage?: UmzugStorage<Ctx>
  /** An optional context object, which will be passed to each migration function, if defined */
  context?: Ctx | (() => Promise<Ctx> | Ctx)
  /** Options for file creation */
  create?: {
    /**
     * A function for generating placeholder migration files. Specify to make sure files generated via CLI or using `.create` follow team conventions.
     * Should return an array of [filepath, content] pairs. Usually, only one pair is needed, but to put `down` migrations in a separate
     * file, more than one can be returned.
     */
    template?: (filepath: string) => Promisable<Array<[string, string]>>
    /**
     * The default folder that new migration files should be generated in. If this is not specified, the new migration file will be created
     * in the same folder as the last existing migration. The value here can be overriden by passing `folder` when calling `create`.
     */
    folder?: string
  }
}

/** Serializeable metadata for a migration. The structure returned by the external-facing `pending()` and `executed()` methods. */
export type MigrationMeta = {
  /** Name - this is used as the migration unique identifier within storage */
  name: string
  /** An optional filepath for the migration. Note: this may be undefined, since not all migrations correspond to files on the filesystem */
  path?: string
}

export type MigrationParams<T> = {
  name: string
  path?: string
  context: T
}

/** A callable function for applying or reverting a migration  */
export type MigrationFn<T = unknown> = (params: MigrationParams<T>) => Promise<unknown>

/**
 * A runnable migration. Represents a migration object with an `up` function which can be called directly, with no arguments, and an optional `down` function to revert it.
 */
export type RunnableMigration<T> = {
  /** The effect of applying the migration */
  up: MigrationFn<T>
  /** The effect of reverting the migration */
  down?: MigrationFn<T>
} & MigrationMeta

/** Glob instructions for migration files */
export type GlobInputMigrations<T> = {
  /**
   * A glob string for migration files. Can also be in the format `[path/to/migrations/*.js', {cwd: 'some/base/dir', ignore: '**ignoreme.js' }]`
   * See https://npmjs.com/package/glob for more details on the glob format - this package is used internally.
   */
  glob: string | [string, {cwd?: string; ignore?: string | string[]}]
  /** Will be supplied to every migration function. Can be a database client, for example */
  /** A function which takes a migration name, path and context, and returns an object with `up` and `down` functions. */
  resolve?: Resolver<T>
}

/**
 * Allowable inputs for migrations. Can be either glob instructions for migration files, a list of runnable migrations, or a
 * function which receives a context and returns a list of migrations.
 */
export type InputMigrations<T> =
  | GlobInputMigrations<T>
  | Array<RunnableMigration<T>>
  | ((context: T) => Promisable<InputMigrations<T>>)

/** A function which takes a migration name, path and context, and returns an object with `up` and `down` functions. */
export type Resolver<T> = (params: MigrationParams<T>) => RunnableMigration<T>

export const RerunBehavior = {
  /** Hard error if an up migration that has already been run, or a down migration that hasn't, is encountered */
  THROW: 'THROW',
  /** Silently skip up migrations that have already been run, or down migrations that haven't */
  SKIP: 'SKIP',
  /** Re-run up migrations that have already been run, or down migrations that haven't */
  ALLOW: 'ALLOW',
} as const

// eslint-disable-next-line @typescript-eslint/no-redeclare
export type RerunBehavior = keyof typeof RerunBehavior

export type MigrateUpOptions = MergeExclusive<
  {
    /** If specified, migrations up to and including this name will be run. Otherwise, all pending migrations will be run */
    to?: string
  },
  {
    /** Only run this many migrations. If not specified, all pending migrations will be run */
    step: number
  },
  {
    /** If specified, only the migrations with these names migrations will be run. An error will be thrown if any of the names are not found in the list of available migrations */
    migrations: string[]

    /** What to do if a migration that has already been run is explicitly specified. Default is `THROW`. */
    rerun?: RerunBehavior
  }
>

export type MigrateDownOptions = MergeExclusive<
  {
    /** If specified, migrations down to and including this name will be revert. Otherwise, only the last executed will be reverted */
    to?: string | 0
  },
  {
    /** Revert this many migrations. If not specified, only the most recent migration will be reverted */
    step: number
  },
  {
    /**
     * If specified, only the migrations with these names migrations will be reverted. An error will be thrown if any of the names are not found in the list of executed migrations.
     * Note, migrations will be run in the order specified.
     */
    migrations: string[]

    /** What to do if a migration that has not been run is explicitly specified. Default is `THROW`. */
    rerun?: RerunBehavior
  }
>

/** Map of eventName -> eventData type, where the keys are the string events that are emitted by an umzug instances, and the values are the payload emitted with the corresponding event. */
export type UmzugEvents<Ctx> = {
  migrating: MigrationParams<Ctx>
  migrated: MigrationParams<Ctx>
  reverting: MigrationParams<Ctx>
  reverted: MigrationParams<Ctx>
  beforeCommand: {command: string; context: Ctx}
  afterCommand: {command: string; context: Ctx}
}