const besUrl = 'http://localhost:225/api/v2/check'

let besEditors = {} // Collection of all editors on page

window.onload = () => {
  // Search and prepare all our editors found in the document.
  document.querySelectorAll('.bes-online-editor').forEach(edit => {
    let editor = {
      timer: null,
      children: [
        {
          elements: null,
          isProofed: false
          // matches: [
          //   {
          //     range: null,
          //     rects: null
          //   }
          // ]
        }
      ]
    }
    besEditors[edit.id] = editor
    besProof(edit)
    edit.addEventListener(
      'beforeinput',
      e => besHandleBeforeInput(edit.id, e),
      false
    )
    edit.addEventListener('click', e => besHandleClick(e, edit))
    // TODO: Handle editor resizes.
  })
}

// Recursively grammar-proofs one node.
async function besProof(el) {
  switch (el.nodeType) {
    case Node.TEXT_NODE:
      return [{ text: el.textContent, el: el, markup: false }]

    case Node.ELEMENT_NODE:
      if (besIsBlockElement(el)) {
        // Block elements are grammar-proofed independently.
        if (besIsProofed(el)) {
          return [{ text: '<' + el.tagName + '/>', el: el, markup: true }]
        }
        besClearAllMistakes(el)
        let data = []
        for (const el2 of el.childNodes) {
          data = data.concat(await besProof(el2))
        }
        if (data.some(x => !x.markup && !/^\s*$/.test(x.text))) {
          const requestData = {
            format: 'plain',
            data: JSON.stringify({
              annotation: data.map(x =>
                x.markup ? { markup: x.text } : { text: x.text }
              )
            }),
            language: el.lang ? el.lang : 'sl',
            level: 'picky'
          }
          const request = new Request(besUrl, {
            method: 'POST',
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
            body: new URLSearchParams(requestData)
          })
          fetch(request)
            .then(response => {
              if (!response.ok) {
                // TODO: Make connectivity and BesStr issues non-fatal. But show an error sign somewhere in the UI.
                throw new Error('Backend server response was not OK')
              }
              return response.json()
            })
            .then(responseData => {
              let matches = []
              responseData.matches.forEach(match => {
                let range = document.createRange()

                // Locate start of the grammar mistake.
                for (
                  let idx = 0, startingOffset = 0;
                  ;
                  startingOffset += data[idx++].text.length
                ) {
                  if (
                    !data[idx].markup &&
                    /*startingOffset <= match.offset &&*/ match.offset <
                      startingOffset + data[idx].text.length
                  ) {
                    range.setStart(data[idx].el, match.offset - startingOffset)
                    break
                  }
                }

                // Locate end of the grammar mistake.
                let endOffset = match.offset + match.length
                for (
                  let idx = 0, startingOffset = 0;
                  ;
                  startingOffset += data[idx++].text.length
                ) {
                  if (
                    !data[idx].markup &&
                    /*startingOffset <= endOffset &&*/ endOffset <=
                      startingOffset + data[idx].text.length
                  ) {
                    range.setEnd(data[idx].el, endOffset - startingOffset)
                    break
                  }
                }

                const clientRect = besAddMistake(range, match)
                matches.push({
                  range: range,
                  rects: clientRect,
                  message: match.message
                })
              })

              besMarkProofed(el, matches)
            })
            .catch(error => {
              // TODO: Make parsing issues non-fatal. But show an error sign somewhere in the UI.
              throw new Error(
                'Parsing backend server response failed: ' + error
              )
            })
        }
        return [{ text: '<' + el.tagName + '/>', el: el, markup: true }]
      } else {
        // Surround inline element with dummy <tagName>...</tagName>.
        let data = [{ text: '<' + el.tagName + '>', el: el, markup: true }]
        for (const el2 of el.childNodes) {
          data = data.concat(await besProof(el2))
        }
        data.splice(data.length, 0, {
          text: '</' + el.tagName + '>',
          markup: true
        })
        return data
      }

    default:
      return [{ text: '<?' + el.nodeType + '>', el: el, markup: true }]
  }
}

// Marks section of text that is about to change as not-yet-grammar-proofed.
function besHandleBeforeInput(editorId, event) {
  let editor = besEditors[editorId]
  if (editor.timer) clearTimeout(editor.timer)
  editor.timer = setTimeout(function () {
    besProof(edit)
  }, 1000)

  // No need to invalidate elements after range.startContainer since they will
  // get either deleted or replaced.
  let edit = document.getElementById(editorId)
  event
    .getTargetRanges()
    .forEach(range =>
      besClearProofed(besGetBlockParent(range.startContainer, edit))
    )
}

// Test if given block element has already been grammar-proofed.
function besIsProofed(el) {
  if (el.id.startsWith('ed')) return
  const editorId = el.parentElement.id
  const editor = besEditors[editorId]
  let filteredChildren = editor?.children.filter(child => child.elements === el)
  return filteredChildren[0]?.isProofed
}

// Mark given block element as grammar-proofed.
function besMarkProofed(el, matches) {
  const editorId = el.parentElement.id
  const editor = besEditors[editorId]
  let newChild = {
    isProofed: true,
    elements: el,
    matches: matches
  }

  editor.children = editor.children.map(child =>
    child.elements === newChild.elements ? newChild : child
  )
  if (!editor.children.some(child => child.elements === newChild.elements)) {
    editor.children.push(newChild)
  }
}

// Mark given block element as not grammar-proofed.
function besClearProofed(el) {
  const editorId = el.parentElement.id
  const editor = besEditors[editorId]
  let filteredChildren = editor.children.filter(child => child.elements === el)
  if (filteredChildren.length) filteredChildren[0].isProofed = false
}

// Remove all grammar mistakes markup for given block element.
function besClearAllMistakes(el) {
  if (el.id.startsWith('ed')) return
  const editorId = el.parentElement.id
  const editor = besEditors[editorId]
  let filteredChildren = editor?.children.filter(child => child.elements === el)
  if (!filteredChildren.length) return

  const correctionPanel = document.getElementById('correction-panel')
  filteredChildren[0].matches.forEach(match => {
    for (const rect of match.rects) {
      for (let child of correctionPanel.children) {
        let childRect = child.getBoundingClientRect()
        const isWithinRect =
          childRect.left >= rect.left &&
          childRect.right <= rect.right &&
          childRect.top >= rect.top &&
          childRect.bottom <= rect.bottom + 20
        if (isWithinRect) {
          child.remove()
        }
      }
    }
  })
}

// Adds grammar mistake markup
function besAddMistake(range, match) {
  const correctionPanel = document.getElementById('correction-panel')
  const clientRects = range.getClientRects()
  for (let i = 0, n = clientRects.length; i < n; ++i) {
    const rect = clientRects[i]
    const highlight = document.createElement('div')
    highlight.classList.add('bes-typo-mistake')
    highlight.dataset.info = match.message
    highlight.style.left = `${rect.left}px`
    highlight.style.top = `${rect.top}px`
    highlight.style.width = `${rect.width}px`
    highlight.style.height = `${rect.height}px`
    correctionPanel.appendChild(highlight)
  }
  return clientRects
}

// Tests if given element is block element.
function besIsBlockElement(el) {
  const defaultView = document.defaultView
  switch (
    defaultView
      .getComputedStyle(el, null)
      .getPropertyValue('display')
      .toLowerCase()
  ) {
    case 'inline':
    case 'inline-block':
      return false
    default:
      return true
  }
}

// Returns first block parent element
function besGetBlockParent(el, edit) {
  for (; el && el !== edit; el = el.parentNode) {
    if (el.nodeType === Node.ELEMENT_NODE && besIsBlockElement(el)) return el
  }
  return el
}

function besHandleClick(e, editor) {
  const targetEl = e.target
  const popup = document.querySelector('bes-popup-el')
  if (targetEl.tagName === 'DIV') {
    const editorData = besEditors[editor.id]
    const divIndex = editorData.children.findIndex(
      child => child.elements === targetEl
    )
    const matches = editorData.children[divIndex]?.matches
    if (!matches) {
      popup.hide()
      return
    }
    if (besRenderPopup(matches, popup, e.clientX, e.clientY)) return
  } else {
    popup.hide()
  }
}

function besRenderPopup(matches, popup, clientX, clientY) {
  for (let m of matches) {
    if (m.rects) {
      for (let r of m.rects) {
        if (besIsPointInRect(clientX, clientY, r)) {
          popup.changeText(m.message)
          popup.show(clientX, clientY)
          return true
        }
      }
    } else {
      popup.hide()
    }
  }
  return false
}

function besIsPointInRect(x, y, rect) {
  return (
    x >= rect.x &&
    x <= rect.x + rect.width &&
    y >= rect.y &&
    y <= rect.y + rect.height
  )
}