import {Directive, OptionDefinition, CLIDirective} from '../../cli'
import {Container, Inject, Injectable} from '../../di'
import {Collection} from '../../util'
import {Bus, EventHandlerSubscription} from '../../support/bus'
import {Migrations} from '../services/Migrations'
import {Migrator} from '../migrations/Migrator'
import {ApplyingMigrationEvent} from '../migrations/events/ApplyingMigrationEvent'
import {AppliedMigrationEvent} from '../migrations/events/AppliedMigrationEvent'
import {NothingToMigrateError} from '../migrations/NothingToMigrateError'

/**
 * CLI directive that applies migrations using the default Migrator.
 * @fixme Support dry run mode
 */
@Injectable()
@CLIDirective()
export class MigrateDirective extends Directive {
    @Inject()
    protected readonly bus!: Bus

    @Inject('injector')
    protected readonly injector!: Container

    /** Event bus subscriptions. */
    protected subscriptions: Collection<EventHandlerSubscription> = new Collection()

    getKeywords(): string | string[] {
        return ['migrate']
    }

    getDescription(): string {
        return 'apply pending migrations'
    }

    getOptions(): OptionDefinition[] {
        return [
            '--package -p {name} | apply migrations for a specific namespace',
            '--identifier -i {name} | apply a specific migration, by identifier',
        ]
    }

    getHelpText(): string {
        return [
            'Migrations are single-run code patches used to track changes to things like database schemata.',
            '',
            'You can create migrations in your app using the ./ex command and they can be applied and rolled-back.',
            '',
            './ex migrate:create "Add version column to sessions table"',
            '',
            'Modules and packages can also register their own migrations. These are run by default.',
            '',
            'To run the migrations for a specific package, and no others, use the --package option. Example:',
            '',
            './ex migrate --package @extollo',
            '',
        ].join('\n')
    }

    async handle(): Promise<void> {
        await this.registerListeners()

        const namespace = this.option('package')
        const identifier = this.option('identifier')

        let identifiers
        if ( namespace ) {
            identifiers = (this.injector.make<Migrations>(Migrations))
                .all(namespace)
                .map(id => `${namespace}:${id}`)
        }

        if ( identifier ) {
            if ( !identifiers ) {
                identifiers = [identifier]
            }

            identifiers = identifiers.filter(x => x === identifier)
        }

        let error
        try {
            await (this.injector.make<Migrator>(Migrator)).migrate(identifiers)
        } catch (e) {
            if ( e instanceof NothingToMigrateError ) {
                this.info(e.message)
            } else {
                error = e
                this.error(e)
            }
        } finally {
            await this.removeListeners()
        }

        if ( error ) {
            throw error
        }
    }

    /**
     * Register event bus listeners to print messages for the user.
     * @protected
     */
    protected async registerListeners(): Promise<void> {
        this.subscriptions.push(await this.bus.subscribe(ApplyingMigrationEvent, event => {
            this.info(`Applying migration ${event.migration.identifier}...`)
        }))

        this.subscriptions.push(await this.bus.subscribe(AppliedMigrationEvent, event => {
            this.success(`Applied migration: ${event.migration.identifier}`)
        }))
    }

    /** Remove event bus listeners before finish. */
    protected async removeListeners(): Promise<void> {
        await this.subscriptions.awaitMapCall('unsubscribe')
    }
}