// ==UserScript==
// @name                 Discourse Prevent Jump on Reply
// @name:zh-CN           Discourse 回复时防止跳转
// @namespace            https://github.com/utags
// @homepageURL          https://github.com/utags/userscripts#readme
// @supportURL           https://github.com/utags/userscripts/issues
// @version              0.1.1
// @description          Prevent Discourse from jumping after posting a reply by intercepting the reply button click and forcing shiftKey, keeping scroll position and context.
// @description:zh-CN    拦截回复按钮点击并强制 shiftKey，避免发帖后页面跳转，保持当前位置与上下文。
// @author               Pipecraft
// @license              MIT
// @icon                 https://www.google.com/s2/favicons?sz=64&domain=meta.discourse.org
// @match                https://meta.discourse.org/*
// @match                https://linux.do/*
// @match                https://idcflare.com/*
// @match                https://www.nodeloc.com/*
// @match                https://meta.appinn.net/*
// @noframes
// @run-at               document-idle
// @grant                GM.getValue
// @grant                GM.setValue
// ==/UserScript==ss

;(() => {
  'use strict'

  const SELECTOR_REPLY_BUTTON =
    '.composer-action-reply .save-or-cancel button.create'
  const I18N_LABEL = {
    en: 'Prevent jump to latest post',
    'zh-CN': '防止跳转到最新帖子',
  }
  function getDiscourseLocale() {
    try {
      const htmlLang = (
        document.documentElement.getAttribute('lang') || ''
      ).toLowerCase()
      if (htmlLang) return htmlLang
      const bodyLang =
        (document.body && document.body.getAttribute('lang')) || ''
      if (bodyLang) return bodyLang.toLowerCase()
      const classes = (document.documentElement.className || '').toLowerCase()
      const m = classes.match(/\blocale-([a-z-]+)/)
      if (m && m[1]) return m[1]
      const meta =
        document.querySelector('meta[name="language"]') ||
        document.querySelector('meta[http-equiv="content-language"]')
      const metaLang = meta && meta.content ? meta.content.toLowerCase() : ''
      if (metaLang) return metaLang
    } catch {}
    return ''
  }
  function getLang() {
    const l =
      getDiscourseLocale() || String(navigator.language || '').toLowerCase()
    return l.startsWith('zh') ? 'zh-CN' : 'en'
  }

  const inited = new WeakSet()
  function register(button) {
    if (!button || inited.has(button)) return
    inited.add(button)
    ensureToggle(button)

    button.addEventListener(
      'click',
      function (originalEvent) {
        if (!getEnabled() || originalEvent.shiftKey) return
        originalEvent.stopImmediatePropagation()
        originalEvent.preventDefault()
        const newEvent = new MouseEvent('click', {
          bubbles: originalEvent.bubbles,
          cancelable: originalEvent.cancelable,
          clientX: originalEvent.clientX,
          clientY: originalEvent.clientY,
          shiftKey: true,
          altKey: originalEvent.altKey,
          ctrlKey: originalEvent.ctrlKey,
          metaKey: originalEvent.metaKey,
          button: originalEvent.button,
          buttons: originalEvent.buttons,
        })
        originalEvent.target.dispatchEvent(newEvent)
      },
      true
    )
  }

  function scan() {
    const list = document.querySelectorAll(SELECTOR_REPLY_BUTTON)
    list.forEach((b) => register(b))
  }

  function getActiveReplyButton() {
    const list = document.querySelectorAll(SELECTOR_REPLY_BUTTON)
    return Array.from(list).find((b) => !!b.offsetParent) || list[0] || null
  }

  document.addEventListener(
    'keydown',
    (e) => {
      if (
        getEnabled() &&
        (e.metaKey || e.ctrlKey) &&
        (e.key === 'Enter' || e.code === 'Enter')
      ) {
        e.stopImmediatePropagation()
        e.preventDefault()
        const btn = getActiveReplyButton()
        if (btn) {
          const ev = new MouseEvent('click', {
            bubbles: true,
            cancelable: true,
            shiftKey: true,
          })
          btn.dispatchEvent(ev)
        }
      }
    },
    true
  )

  const KEY = 'dpjor_enabled:' + (location.hostname || '')
  let enabledFlag = false
  function getEnabled() {
    return !!enabledFlag
  }
  async function loadEnabled() {
    try {
      const val = await GM.getValue(KEY, '0')
      enabledFlag = val === '1' || val === true
      updateToggleUI()
    } catch {
      enabledFlag = false
    }
  }
  function setEnabled(v) {
    enabledFlag = !!v
    try {
      GM.setValue(KEY, v ? '1' : '0')
    } catch {}
  }
  function updateToggleUI() {
    try {
      document
        .querySelectorAll('.dpjor-toggle input[type="checkbox"]')
        .forEach((cb) => (cb.checked = getEnabled()))
    } catch {}
  }
  function ensureToggle(button) {
    const container = button.closest('.save-or-cancel') || button.parentElement
    if (!container || container.querySelector('.dpjor-toggle')) return
    const label = document.createElement('label')
    label.className = 'dpjor-toggle'
    label.style.marginLeft = '8px'
    label.style.display = 'inline-flex'
    label.style.alignItems = 'center'
    label.style.gap = '6px'
    const cb = document.createElement('input')
    cb.type = 'checkbox'
    cb.checked = getEnabled()
    const span = document.createElement('span')
    span.textContent = I18N_LABEL[getLang()] || I18N_LABEL.en
    cb.addEventListener('change', () => setEnabled(cb.checked))
    label.appendChild(cb)
    label.appendChild(span)
    container.appendChild(label)
  }

  loadEnabled()
  scan()
  const mo = new MutationObserver(() => scan())
  mo.observe(document.documentElement || document.body, {
    childList: true,
    subtree: true,
  })
})()