import { ScoreInfo } from './scoreinfo'
import { loadMscore, WebMscore } from './mscore'
import { useTimeout, windowOpenAsync, console, attachShadow, DISCORD_URL } from './utils'
import { isGmAvailable, _GM } from './gm'
import i18n from './i18n'
// @ts-ignore
import btnListCss from './btn.css'

type BtnElement = HTMLButtonElement

export enum ICON {
  DOWNLOAD = 'M9.6 2.4h4.8V12h2.784l-5.18 5.18L6.823 12H9.6V2.4zM19.2 19.2H4.8v2.4h14.4v-2.4z',
  LIBRESCORE = 'm5.4837 4.4735v10.405c-1.25-0.89936-3.0285-0.40896-4.1658 0.45816-1.0052 0.76659-1.7881 2.3316-0.98365 3.4943 1 1.1346 2.7702 0.70402 3.8817-0.02809 1.0896-0.66323 1.9667-1.8569 1.8125-3.1814v-5.4822h8.3278v9.3865h9.6438v-2.6282h-6.4567v-12.417c-4.0064-0.015181-8.0424-0.0027-12.06-0.00676zm0.54477 2.2697h8.3278v1.1258h-8.3278v-1.1258z',
}

const getBtnContainer = (): HTMLDivElement => {
  const els = [...document.querySelectorAll('span')]
  const el = els.find(b => {
    const text = b?.textContent?.replace(/\s/g, '') || ''
    return text.includes('Download') || text.includes('Print')
  }) as HTMLDivElement | null
  const btnParent = el?.parentElement?.parentElement as HTMLDivElement | undefined
  if (!btnParent || !(btnParent instanceof HTMLDivElement)) throw new Error('btn parent not found')
  return btnParent
}

const buildDownloadBtn = (icon: ICON, lightTheme = false) => {
  const btn = document.createElement('button')
  btn.type = 'button'
  if (lightTheme) btn.className = 'light'

  // build icon svg element
  const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg')
  svg.setAttribute('viewBox', '0 0 24 24')
  const svgPath = document.createElementNS('http://www.w3.org/2000/svg', 'path')
  svgPath.setAttribute('d', icon)
  svgPath.setAttribute('fill', lightTheme ? '#2e68c0' : '#fff')
  svg.append(svgPath)

  const textNode = document.createElement('span')
  btn.append(svg, textNode)

  return btn
}

const cloneBtn = (btn: HTMLButtonElement) => {
  const n = btn.cloneNode(true) as HTMLButtonElement
  n.onclick = btn.onclick
  return n
}

function getScrollParent (node: HTMLElement): HTMLElement {
  if (node.scrollHeight > node.clientHeight) {
    return node
  } else {
    return getScrollParent(node.parentNode as HTMLElement)
  }
}

function onPageRendered (getEl: () => HTMLElement) {
  return new Promise<HTMLElement>((resolve) => {
    const observer = new MutationObserver(() => {
      try {
        const el = getEl()
        if (el) {
          observer.disconnect()
          resolve(el)
        }
      } catch { }
    })
    observer.observe(document.querySelector('div > section') ?? document.body, { childList: true, subtree: true })
  })
}

interface BtnOptions {
  readonly name: string;
  readonly action: BtnAction;
  readonly disabled?: boolean;
  readonly tooltip?: string;
  readonly icon?: ICON;
  readonly lightTheme?: boolean;
}

export enum BtnListMode {
  InPage,
  ExtWindow,
}

export class BtnList {
  private readonly list: BtnElement[] = [];

  constructor (private getBtnParent: () => HTMLDivElement = getBtnContainer) { }

  add (options: BtnOptions): BtnElement {
    const btnTpl = buildDownloadBtn(options.icon ?? ICON.DOWNLOAD, options.lightTheme)
    const setText = (btn: BtnElement) => {
      const textNode = btn.querySelector('span')
      return (str: string): void => {
        if (textNode) textNode.textContent = str
      }
    }

    setText(btnTpl)(options.name)

    btnTpl.onclick = function () {
      const btn = this as BtnElement
      options.action(options.name, btn, setText(btn))
    }

    this.list.push(btnTpl)

    if (options.disabled) {
      btnTpl.disabled = options.disabled
    }

    if (options.tooltip) {
      btnTpl.title = options.tooltip
    }

    // add buttons to the userscript manager menu
    if (isGmAvailable('registerMenuCommand')) {
      // eslint-disable-next-line no-void
      void _GM.registerMenuCommand(options.name, () => {
        options.action(options.name, btnTpl, () => undefined)
      })
    }

    return btnTpl
  }

  private _positionBtns (anchorDiv: HTMLDivElement, newParent: HTMLDivElement) {
    let { top } = anchorDiv.getBoundingClientRect()
    top += window.scrollY // relative to the entire document instead of viewport
    if (top > 0) {
      newParent.style.top = `${top}px`
    } else {
      newParent.style.top = '0px'
    }
  }

  private _commit () {
    const btnParent = document.querySelector('div') as HTMLDivElement
    const shadow = attachShadow(btnParent)

    // style the shadow DOM
    const style = document.createElement('style')
    style.innerText = btnListCss
    shadow.append(style)

    // hide buttons using the shadow DOM
    const slot = document.createElement('slot')
    shadow.append(slot)

    const newParent = document.createElement('div')
    newParent.append(...this.list.map(e => cloneBtn(e)))
    shadow.append(newParent)

    // default position
    newParent.style.top = `${window.innerHeight - newParent.getBoundingClientRect().height}px`

    void onPageRendered(this.getBtnParent).then((anchorDiv: HTMLDivElement) => {
      const pos = () => this._positionBtns(anchorDiv, newParent)
      pos()

      // reposition btns when window resizes
      window.addEventListener('resize', pos, { passive: true })

      // reposition btns when scrolling
      const scroll = getScrollParent(anchorDiv)
      scroll.addEventListener('scroll', pos, { passive: true })
    })

    return btnParent
  }

  /**
   * replace the template button with the list of new buttons
   */
  async commit (mode: BtnListMode = BtnListMode.InPage): Promise<void> {
    switch (mode) {
      case BtnListMode.InPage: {
        let el: Element
        try {
          el = this._commit()
        } catch {
          // fallback to BtnListMode.ExtWindow
          return this.commit(BtnListMode.ExtWindow)
        }
        const observer = new MutationObserver(() => {
          // check if the buttons are still in document when dom updates 
          if (!document.contains(el)) {
            // re-commit
            // performance issue?
            el = this._commit()
          }
        })
        observer.observe(document, { childList: true, subtree: true })
        break
      }

      case BtnListMode.ExtWindow: {
        const div = this._commit()
        const w = await windowOpenAsync(undefined, '', undefined, 'resizable,width=230,height=270')
        // eslint-disable-next-line no-unused-expressions
        w?.document.body.append(div)
        window.addEventListener('unload', () => w?.close())
        break
      }

      default:
        throw new Error('unknown BtnListMode')
    }
  }
}

type BtnAction = (btnName: string, btnEl: BtnElement, setText: (str: string) => void) => any

// eslint-disable-next-line @typescript-eslint/no-namespace
export namespace BtnAction {

  type Promisable<T> = T | Promise<T>
  type UrlInput = Promisable<string> | (() => Promisable<string>)

  const normalizeUrlInput = (url: UrlInput) => {
    if (typeof url === 'function') return url()
    else return url
  }

  export const download = (url: UrlInput, fallback?: () => Promisable<void>, timeout?: number, target?: '_blank'): BtnAction => {
    return process(async (): Promise<void> => {
      const _url = await normalizeUrlInput(url)
      const a = document.createElement('a')
      a.href = _url
      if (target) a.target = target
      a.dispatchEvent(new MouseEvent('click'))
    }, fallback, timeout)
  }

  export const openUrl = download

  export const mscoreWindow = (scoreinfo: ScoreInfo, fn: (w: Window, score: WebMscore, processingTextEl: ChildNode) => any): BtnAction => {
    return async (btnName, btn, setText) => {
      const _onclick = btn.onclick
      btn.onclick = null
      setText(i18n('PROCESSING')())

      const w = await windowOpenAsync(btn, '') as Window
      const txt = document.createTextNode(i18n('PROCESSING')())
      w.document.body.append(txt)

      // set page hooks
      // eslint-disable-next-line prefer-const
      let score: WebMscore
      const destroy = (): void => {
        score && score.destroy()
        w.close()
      }
      window.addEventListener('unload', destroy)
      w.addEventListener('beforeunload', () => {
        score && score.destroy()
        window.removeEventListener('unload', destroy)
        setText(btnName)
        btn.onclick = _onclick
      })

      score = await loadMscore(scoreinfo, w)

      fn(w, score, txt)
    }
  }

  export const process = (fn: () => any, fallback?: () => Promisable<void>, timeout = 10 * 60 * 1000 /* 10min */): BtnAction => {
    return async (name, btn, setText): Promise<void> => {
      const _onclick = btn.onclick

      btn.onclick = null
      setText(i18n('PROCESSING')())

      try {
        await useTimeout(fn(), timeout)
        setText(name)
      } catch (err) {
        console.error(err)
        if (fallback) {
          // use fallback
          await fallback()
          setText(name)
        } else {
          setText(i18n('BTN_ERROR')())
          // ask user to send Discord message
          alert(
            '❌Download Failed!\n\n' +
            'Send your URL to the #dataset-bugs channel ' +
            'in the LibreScore Community Discord server:\n' + DISCORD_URL,
          )
          // open Discord on 'OK'
          const a = document.createElement('a')
          a.href = DISCORD_URL
          a.target = '_blank'
          a.dispatchEvent(new MouseEvent('click'))
        }
      }

      btn.onclick = _onclick
    }
  }

  export const deprecate = (action: BtnAction): BtnAction => {
    return (name, btn, setText) => {
      alert(i18n('DEPRECATION_NOTICE')(name))
      // eslint-disable-next-line @typescript-eslint/no-unsafe-return
      return action(name, btn, setText)
    }
  }

}