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('.online-editor').forEach(edit => {
    let editor = {
      timer: null
    }
    besEditors[edit.id] = editor
    besProof(edit)
    edit.addEventListener('beforeinput', e => besHandleBeforeInput(edit.id, e), false)
    edit.addEventListener('click', e => besHandleClick(e))
    // 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: '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 => {
              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
                  }
                }

                besAddMistake(range, match)
              })

              besMarkProofed(el)
            })
            .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)
{
  return el.getAttribute('besProofed') === 'true'
}

// Mark given block element as grammar-proofed.
function besMarkProofed(el)
{
  el.setAttribute('besProofed', 'true')
}

// Mark given block element as not grammar-proofed.
function besClearProofed(el)
{
  el?.removeAttribute('besProofed')
}

// Remove all grammar mistakes markup for given block element.
function besClearAllMistakes(el) {
  for (const el2 of el.childNodes) {
    if (el2.tagName === 'SPAN' && el2.classList.contains('typo-mistake')) {
      el2.replaceWith(...el2.childNodes)
      el2.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("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);

    // TODO: Find a solution to handle click events on the highlights
    // const editor = document.querySelector('.online-editor')
    // highlight.addEventListener("click", function(e) {
      // console.log(e);
      // editor.focus();
      // besHandleClick(e);
      // return true;
    // });
  }
}

// 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)
{
  while (el && el !== edit) {
    switch (el.nodeType) {
      case Node.TEXT_NODE:
        el = el.parentNode
        break
  
      case Node.ELEMENT_NODE:
        if (besIsBlockElement(el)) {
          return el
        }
        el = el.parentNode
    }
  }
  return el
}

function besHandleClick(e) {
  switch (e.target) {
    case e.target.closest('span'):
      const clicked = e.target.closest('span')
      const infoText = clicked?.dataset.info
      const myComponent = document.querySelector('my-component')
      myComponent.setAttribute('my-attribute', infoText)
      console.log(clicked)
      break
  }
}