import { Awaitable, camelize, Dict, isNullable, remove } from 'cosmokit'
import { coerce } from '@koishijs/utils'
import { Fragment, Logger, Schema, Universal } from '@satorijs/core'
import { Argv } from './parser'
import { Next, SessionError } from '../middleware'
import { Channel, User } from '../database'
import { FieldCollector, Session } from '../session'
import { Permissions } from '../permission'
import { Context } from '../context'
import { Computed } from '../filter'

const logger = new Logger('command')

export type Extend<O extends {}, K extends string, T> = {
  [P in K | keyof O]?: (P extends keyof O ? O[P] : unknown) & (P extends K ? T : unknown)
}

export namespace Command {
  export interface Alias {
    options?: Dict
    args?: string[]
    filter?: Computed<boolean>
  }

  export interface Shortcut {
    i18n?: boolean
    name?: string | RegExp
    command?: Command
    prefix?: boolean
    fuzzy?: boolean
    args?: string[]
    options?: Dict
  }

  export type Action<U extends User.Field = never, G extends Channel.Field = never, A extends any[] = any[], O extends {} = {}>
    = (argv: Argv<U, G, A, O>, ...args: A) => Awaitable<void | Fragment>

  export type Usage<U extends User.Field = never, G extends Channel.Field = never>
    = string | ((session: Session<U, G>) => Awaitable<string>)
}

export class Command<
  U extends User.Field = never,
  G extends Channel.Field = never,
  A extends any[] = any[],
  O extends {} = {},
> extends Argv.CommandBase<Command.Config> {
  children: Command[] = []

  _parent: Command = null
  _aliases: Dict<Command.Alias> = Object.create(null)
  _examples: string[] = []
  _usage?: Command.Usage

  private _userFields: FieldCollector<'user'>[] = [['locales']]
  private _channelFields: FieldCollector<'channel'>[] = [['locales']]
  private _actions: Command.Action[] = []
  private _checkers: Command.Action[] = [async (argv) => {
    return this.ctx.serial(argv.session, 'command/before-execute', argv)
  }]

  constructor(name: string, decl: string, ctx: Context, config: Command.Config) {
    super(name, decl, ctx, {
      showWarning: true,
      handleError: true,
      slash: true,
      ...config,
    })
    this.config.permissions ??= [`authority:${config?.authority ?? 1}`]
    this._registerAlias(name)
    ctx.$commander._commandList.push(this)
  }

  get caller(): Context {
    return this[Context.current] || this.ctx
  }

  get displayName() {
    return Object.keys(this._aliases)[0]
  }

  set displayName(name) {
    this._registerAlias(name, true)
  }

  get parent() {
    return this._parent
  }

  set parent(parent: Command) {
    if (this._parent === parent) return
    if (this._parent) {
      remove(this._parent.children, this)
    }
    this._parent = parent
    if (parent) {
      parent.children.push(this)
    }
  }

  static normalize(name: string) {
    return name.toLowerCase().replace(/_/g, '-')
  }

  private _registerAlias(name: string, prepend = false, options: Command.Alias = {}) {
    name = Command.normalize(name)
    if (name.startsWith('.')) name = this.parent.name + name

    // check global
    const previous = this.ctx.$commander.get(name)
    if (previous && previous !== this) {
      throw new Error(`duplicate command names: "${name}"`)
    }

    // add to list
    const existing = this._aliases[name]
    if (existing) {
      if (prepend) {
        this._aliases = { [name]: existing, ...this._aliases }
      }
    } else if (prepend) {
      this._aliases = { [name]: options, ...this._aliases }
    } else {
      this._aliases[name] = options
    }
  }

  [Symbol.for('nodejs.util.inspect.custom')]() {
    return `Command <${this.name}>`
  }

  userFields<T extends User.Field>(fields: FieldCollector<'user', T, A, O>): Command<U | T, G, A, O> {
    this._userFields.push(fields)
    return this as any
  }

  channelFields<T extends Channel.Field>(fields: FieldCollector<'channel', T, A, O>): Command<U, G | T, A, O> {
    this._channelFields.push(fields)
    return this as any
  }

  alias(...names: string[]): this
  alias(name: string, options: Command.Alias): this
  alias(...args: any[]) {
    if (typeof args[1] === 'object') {
      this._registerAlias(args[0], false, args[1])
    } else {
      for (const name of args) {
        this._registerAlias(name)
      }
    }
    this.caller.emit('command-updated', this)
    return this
  }

  _escape(source: any) {
    if (typeof source !== 'string') return source
    return source
      .replace(/\$\$/g, '@@__PLACEHOLDER__@@')
      .replace(/\$\d/g, s => `{${s[1]}}`)
      .replace(/@@__PLACEHOLDER__@@/g, '$')
  }

  /** @deprecated please use `cmd.alias()` instead */
  shortcut(pattern: string | RegExp, config?: Command.Shortcut & { i18n?: false }): this
  /** @deprecated please use `cmd.alias()` instead */
  shortcut(pattern: string, config: Command.Shortcut & { i18n: true }): this
  shortcut(pattern: string | RegExp, config: Command.Shortcut = {}) {
    let content = this.displayName
    for (const key in config.options || {}) {
      content += ` --${camelize(key)}`
      const value = config.options[key]
      if (value !== true) {
        content += ' ' + this._escape(value)
      }
    }
    for (const arg of config.args || []) {
      content += ' ' + this._escape(arg)
    }
    if (config.fuzzy) content += ' {1}'
    const regex = config.i18n
    if (typeof pattern === 'string') {
      if (config.i18n) {
        pattern = `commands.${this.name}.shortcuts.${pattern}`
      } else {
        config.i18n = true
        const key = `commands.${this.name}.shortcuts._${Math.random().toString(36).slice(2)}`
        this.ctx.i18n.define('', key, pattern)
        pattern = key
      }
    }
    const dispose = this.ctx.match(pattern, `<execute>${content}</execute>`, {
      appel: config.prefix,
      fuzzy: config.fuzzy,
      i18n: config.i18n as never,
      regex,
    })
    this._disposables.push(dispose)
    return this
  }

  subcommand<D extends string>(def: D, config?: Command.Config): Command<never, never, Argv.ArgumentType<D>>
  subcommand<D extends string>(def: D, desc: string, config?: Command.Config): Command<never, never, Argv.ArgumentType<D>>
  subcommand(def: string, ...args: any[]) {
    def = this.name + (def.charCodeAt(0) === 46 ? '' : '/') + def
    const desc = typeof args[0] === 'string' ? args.shift() as string : ''
    const config = args[0] as Command.Config || {}
    return this.ctx.command(def, desc, config)
  }

  usage(text: Command.Usage<U, G>) {
    this._usage = text
    return this
  }

  example(example: string) {
    this._examples.push(example)
    return this
  }

  option<K extends string>(name: K, desc: string, config: Argv.TypedOptionConfig<RegExp>): Command<U, G, A, Extend<O, K, string>>
  option<K extends string, R>(name: K, desc: string, config: Argv.TypedOptionConfig<(source: string) => R>): Command<U, G, A, Extend<O, K, R>>
  option<K extends string, R extends string>(name: K, desc: string, config: Argv.TypedOptionConfig<R[]>): Command<U, G, A, Extend<O, K, R>>
  option<K extends string, D extends string>(name: K, desc: D, config?: Argv.OptionConfig): Command<U, G, A, Extend<O, K, Argv.OptionType<D>>>
  option(name: string, ...args: [Argv.OptionConfig?] | [string, Argv.OptionConfig?]) {
    let desc = ''
    if (typeof args[0] === 'string') {
      desc = args.shift() as string
    }
    const config = { ...args[0] as Argv.OptionConfig }
    config.permissions ??= [`authority:${config.authority ?? 0}`]
    this._createOption(name, desc, config)
    this.caller.emit('command-updated', this)
    this.caller.collect('option', () => this.removeOption(name))
    return this
  }

  match(session: Session) {
    return this.ctx.filter(session)
  }

  check(callback: Command.Action<U, G, A, O>, append = false) {
    return this.before(callback, append)
  }

  before(callback: Command.Action<U, G, A, O>, append = false) {
    if (append) {
      this._checkers.push(callback)
    } else {
      this._checkers.unshift(callback)
    }
    this.caller.scope.disposables?.push(() => remove(this._checkers, callback))
    return this
  }

  action(callback: Command.Action<U, G, A, O>, prepend = false) {
    if (prepend) {
      this._actions.unshift(callback)
    } else {
      this._actions.push(callback)
    }
    this.caller.scope.disposables?.push(() => remove(this._actions, callback))
    return this
  }

  /** @deprecated */
  use<T extends Command, R extends any[]>(callback: (command: this, ...args: R) => T, ...args: R): T {
    return callback(this, ...args)
  }

  async execute(argv: Argv<U, G, A, O>, fallback: Next = Next.compose): Promise<Fragment> {
    argv.command ??= this
    argv.args ??= [] as any
    argv.options ??= {} as any

    const { args, options, error } = argv
    if (error) return error
    if (logger.level >= 3) logger.debug(argv.source ||= this.stringify(args, options))

    // before hooks
    for (const validator of this._checkers) {
      const result = await validator.call(this, argv, ...args)
      if (!isNullable(result)) return result
    }

    // FIXME empty actions will cause infinite loop
    if (!this._actions.length) return ''

    let index = 0
    const queue: Next.Queue = this._actions.map(action => async () => {
      return await action.call(this, argv, ...args)
    })

    queue.push(fallback)
    const length = queue.length
    argv.next = async (callback) => {
      if (callback !== undefined) {
        queue.push(next => Next.compose(callback, next))
        if (queue.length > Next.MAX_DEPTH) {
          throw new Error(`middleware stack exceeded ${Next.MAX_DEPTH}`)
        }
      }
      return queue[index++]?.(argv.next)
    }

    try {
      const result = await argv.next()
      if (!isNullable(result)) return result
    } catch (error) {
      if (index === length) throw error
      if (error instanceof SessionError) {
        return argv.session.text(error.path, error.param)
      }
      const stack = coerce(error)
      logger.warn(`${argv.source ||= this.stringify(args, options)}\n${stack}`)
      this.ctx.emit(argv.session, 'command-error', argv, error)
      if (typeof this.config.handleError === 'function') {
        const result = await this.config.handleError(error, argv)
        if (!isNullable(result)) return result
      } else if (this.config.handleError) {
        return argv.session.text('internal.error-encountered')
      }
    }

    return ''
  }

  dispose() {
    this._disposables.splice(0).forEach(dispose => dispose())
    this.ctx.emit('command-removed', this)
    for (const cmd of this.children.slice()) {
      cmd.dispose()
    }
    remove(this.ctx.$commander._commandList, this)
    this.parent = null
  }

  toJSON(): Universal.Command {
    return {
      name: this.name,
      description: this.ctx.i18n.get(`commands.${this.name}.description`),
      arguments: this._arguments.map(arg => ({
        name: arg.name,
        type: toStringType(arg.type),
        description: this.ctx.i18n.get(`commands.${this.name}.arguments.${arg.name}`),
        required: arg.required,
      })),
      options: Object.entries(this._options).map(([name, option]) => ({
        name,
        type: toStringType(option.type),
        description: this.ctx.i18n.get(`commands.${this.name}.options.${name}`),
        required: option.required,
      })),
      children: this.children
        .filter(child => child.name.includes('.'))
        .map(child => child.toJSON()),
    }
  }
}

function toStringType(type: Argv.Type) {
  return typeof type === 'string' ? type : 'string'
}

export namespace Command {
  export interface Config extends Argv.CommandBase.Config, Permissions.Config {
    captureQuote?: boolean
    /** disallow unknown options */
    checkUnknown?: boolean
    /** check argument count */
    checkArgCount?: boolean
    /** show command warnings */
    showWarning?: boolean
    /** handle error */
    handleError?: boolean | ((error: Error, argv: Argv) => Awaitable<void | Fragment>)
    /** enable slash command */
    slash?: boolean
  }

  export const Config: Schema<Config> = Schema.object({
    permissions: Schema.array(String).role('perms').default(['authority:1']).description('权限继承。'),
    dependencies: Schema.array(String).role('perms').description('权限依赖。'),
    slash: Schema.boolean().description('启用斜线指令功能。').default(true),
    captureQuote: Schema.boolean().description('是否捕获引用文本。').default(true).hidden(),
    checkUnknown: Schema.boolean().description('是否检查未知选项。').default(false).hidden(),
    checkArgCount: Schema.boolean().description('是否检查参数数量。').default(false).hidden(),
    showWarning: Schema.boolean().description('是否显示警告。').default(true).hidden(),
    handleError: Schema.union([Schema.boolean(), Schema.function()]).description('是否处理错误。').default(true).hidden(),
  })
}