let tree;

(async () => {
  const CAPTURE_REGEX = /@\s*([\w._-]+)/g;
  const COLORS_BY_INDEX = [
    'blue',
    'chocolate',
    'darkblue',
    'darkcyan',
    'darkgreen',
    'darkred',
    'darkslategray',
    'dimgray',
    'green',
    'indigo',
    'navy',
    'red',
    'sienna',
  ];

  const codeInput = document.getElementById('code-input');
  const languageSelect = document.getElementById('language-select');
  const loggingCheckbox = document.getElementById('logging-checkbox');
  const outputContainer = document.getElementById('output-container');
  const outputContainerScroll = document.getElementById('output-container-scroll');
  const playgroundContainer = document.getElementById('playground-container');
  const queryCheckbox = document.getElementById('query-checkbox');
  const queryContainer = document.getElementById('query-container');
  const queryInput = document.getElementById('query-input');
  const updateTimeSpan = document.getElementById('update-time');
  const languagesByName = {};

  loadState();

  await TreeSitter.init();

  const parser = new TreeSitter();
  const codeEditor = CodeMirror.fromTextArea(codeInput, {
    lineNumbers: true,
    showCursorWhenSelecting: true
  });

  const queryEditor = CodeMirror.fromTextArea(queryInput, {
    lineNumbers: true,
    showCursorWhenSelecting: true
  });

  const cluster = new Clusterize({
    rows: [],
    noDataText: null,
    contentElem: outputContainer,
    scrollElem: outputContainerScroll
  });
  const renderTreeOnCodeChange = debounce(renderTree, 50);
  const saveStateOnChange = debounce(saveState, 2000);
  const runTreeQueryOnChange = debounce(runTreeQuery, 50);

  let languageName = languageSelect.value;
  let treeRows = null;
  let treeRowHighlightedIndex = -1;
  let parseCount = 0;
  let isRendering = 0;
  let query;

  codeEditor.on('changes', handleCodeChange);
  codeEditor.on('viewportChange', runTreeQueryOnChange);
  codeEditor.on('cursorActivity', debounce(handleCursorMovement, 150));
  queryEditor.on('changes', debounce(handleQueryChange, 150));

  loggingCheckbox.addEventListener('change', handleLoggingChange);
  queryCheckbox.addEventListener('change', handleQueryEnableChange);
  languageSelect.addEventListener('change', handleLanguageChange);
  outputContainer.addEventListener('click', handleTreeClick);

  handleQueryEnableChange();
  await handleLanguageChange()

  playgroundContainer.style.visibility = 'visible';

  async function handleLanguageChange() {
    const newLanguageName = languageSelect.value;
    if (!languagesByName[newLanguageName]) {
      const url = `${LANGUAGE_BASE_URL}/tree-sitter-${newLanguageName}.wasm`
      languageSelect.disabled = true;
      try {
        languagesByName[newLanguageName] = await TreeSitter.Language.load(url);
      } catch (e) {
        console.error(e);
        languageSelect.value = languageName;
        return
      } finally {
        languageSelect.disabled = false;
      }
    }

    tree = null;
    languageName = newLanguageName;
    parser.setLanguage(languagesByName[newLanguageName]);
    handleCodeChange();
    handleQueryChange();
  }

  async function handleCodeChange(_editor, changes) {
    const newText = `${codeEditor.getValue()}\n`;
    const edits = tree && changes && changes.map(treeEditForEditorChange);

    const start = performance.now();
    if (edits) {
      for (const edit of edits) {
        tree.edit(edit);
      }
    }
    const newTree = parser.parse(newText, tree);
    const duration = (performance.now() - start).toFixed(1);

    updateTimeSpan.innerText = `${duration} ms`;
    if (tree) tree.delete();
    tree = newTree;
    parseCount++;
    renderTreeOnCodeChange();
    runTreeQueryOnChange();
    saveStateOnChange();
  }

  async function renderTree() {
    isRendering++;
    const cursor = tree.walk();

    const currentRenderCount = parseCount;
    let row = '';
    const rows = [];
    let finishedRow = false;
    let visitedChildren = false;
    let indentLevel = 0;

    for (let i = 0;; i++) {
      if (i > 0 && i % 10000 === 0) {
        await new Promise(r => setTimeout(r, 0));
        if (parseCount !== currentRenderCount) {
          cursor.delete();
          isRendering--;
          return;
        }
      }

      let displayName;
      if (cursor.nodeIsMissing) {
        displayName = `MISSING ${cursor.nodeType}`
      } else if (cursor.nodeIsNamed) {
        displayName = cursor.nodeType;
      }

      if (visitedChildren) {
        if (displayName) {
          finishedRow = true;
        }

        if (cursor.gotoNextSibling()) {
          visitedChildren = false;
        } else if (cursor.gotoParent()) {
          visitedChildren = true;
          indentLevel--;
        } else {
          break;
        }
      } else {
        if (displayName) {
          if (finishedRow) {
            row += '</div>';
            rows.push(row);
            finishedRow = false;
          }
          const start = cursor.startPosition;
          const end = cursor.endPosition;
          const id = cursor.nodeId;
          let fieldName = cursor.currentFieldName;
          if (fieldName) {
            fieldName += ': ';
          } else {
            fieldName = '';
          }
          row = `<div>${'  '.repeat(indentLevel)}${fieldName}<a class='plain' href="#" data-id=${id} data-range="${start.row},${start.column},${end.row},${end.column}">${displayName}</a> [${start.row}, ${start.column}] - [${end.row}, ${end.column}]`;
          finishedRow = true;
        }

        if (cursor.gotoFirstChild()) {
          visitedChildren = false;
          indentLevel++;
        } else {
          visitedChildren = true;
        }
      }
    }
    if (finishedRow) {
      row += '</div>';
      rows.push(row);
    }

    cursor.delete();
    cluster.update(rows);
    treeRows = rows;
    isRendering--;
    handleCursorMovement();
  }

  function runTreeQuery(_, startRow, endRow) {
    if (endRow == null) {
      const viewport = codeEditor.getViewport();
      startRow = viewport.from;
      endRow = viewport.to;
    }

    codeEditor.operation(() => {
      const marks = codeEditor.getAllMarks();
      marks.forEach(m => m.clear());

      if (tree && query) {
        const captures = query.captures(
          tree.rootNode,
          {row: startRow, column: 0},
          {row: endRow, column: 0},
        );
        let lastNodeId;
        for (const {name, node} of captures) {
          if (node.id === lastNodeId) continue;
          lastNodeId = node.id;
          const {startPosition, endPosition} = node;
          codeEditor.markText(
            {line: startPosition.row, ch: startPosition.column},
            {line: endPosition.row, ch: endPosition.column},
            {
              inclusiveLeft: true,
              inclusiveRight: true,
              css: `color: ${colorForCaptureName(name)}`
            }
          );
        }
      }
    });
  }

  function handleQueryChange() {
    if (query) {
      query.delete();
      query.deleted = true;
      query = null;
    }

    queryEditor.operation(() => {
      queryEditor.getAllMarks().forEach(m => m.clear());
      if (!queryCheckbox.checked) return;

      const queryText = queryEditor.getValue();

      try {
        query = parser.getLanguage().query(queryText);
        let match;

        let row = 0;
        queryEditor.eachLine((line) => {
          while (match = CAPTURE_REGEX.exec(line.text)) {
            queryEditor.markText(
              {line: row, ch: match.index},
              {line: row, ch: match.index + match[0].length},
              {
                inclusiveLeft: true,
                inclusiveRight: true,
                css: `color: ${colorForCaptureName(match[1])}`
              }
            );
          }
          row++;
        });
      } catch (error) {
        const startPosition = queryEditor.posFromIndex(error.index);
        const endPosition = {
          line: startPosition.line,
          ch: startPosition.ch + (error.length || Infinity)
        };

        if (error.index === queryText.length) {
          if (startPosition.ch > 0) {
            startPosition.ch--;
          } else if (startPosition.row > 0) {
            startPosition.row--;
            startPosition.column = Infinity;
          }
        }

        queryEditor.markText(
          startPosition,
          endPosition,
          {
            className: 'query-error',
            inclusiveLeft: true,
            inclusiveRight: true,
            attributes: {title: error.message}
          }
        );
      }
    });

    runTreeQuery();
    saveQueryState();
  }

  function handleCursorMovement() {
    if (isRendering) return;

    const selection = codeEditor.getDoc().listSelections()[0];
    let start = {row: selection.anchor.line, column: selection.anchor.ch};
    let end = {row: selection.head.line, column: selection.head.ch};
    if (
      start.row > end.row ||
      (
        start.row === end.row &&
        start.column > end.column
      )
    ) {
      const swap = end;
      end = start;
      start = swap;
    }
    const node = tree.rootNode.namedDescendantForPosition(start, end);
    if (treeRows) {
      if (treeRowHighlightedIndex !== -1) {
        const row = treeRows[treeRowHighlightedIndex];
        if (row) treeRows[treeRowHighlightedIndex] = row.replace('highlighted', 'plain');
      }
      treeRowHighlightedIndex = treeRows.findIndex(row => row.includes(`data-id=${node.id}`));
      if (treeRowHighlightedIndex !== -1) {
        const row = treeRows[treeRowHighlightedIndex];
        if (row) treeRows[treeRowHighlightedIndex] = row.replace('plain', 'highlighted');
      }
      cluster.update(treeRows);
      const lineHeight = cluster.options.item_height;
      const scrollTop = outputContainerScroll.scrollTop;
      const containerHeight = outputContainerScroll.clientHeight;
      const offset = treeRowHighlightedIndex * lineHeight;
      if (scrollTop > offset - 20) {
        $(outputContainerScroll).animate({scrollTop: offset - 20}, 150);
      } else if (scrollTop < offset + lineHeight + 40 - containerHeight) {
        $(outputContainerScroll).animate({scrollTop: offset - containerHeight + 40}, 150);
      }
    }
  }

  function handleTreeClick(event) {
    if (event.target.tagName === 'A') {
      event.preventDefault();
      const [startRow, startColumn, endRow, endColumn] = event
        .target
        .dataset
        .range
        .split(',')
        .map(n => parseInt(n));
      codeEditor.focus();
      codeEditor.setSelection(
        {line: startRow, ch: startColumn},
        {line: endRow, ch: endColumn}
      );
    }
  }

  function handleLoggingChange() {
    if (loggingCheckbox.checked) {
      parser.setLogger((message, lexing) => {
        if (lexing) {
          console.log("  ", message)
        } else {
          console.log(message)
        }
      });
    } else {
      parser.setLogger(null);
    }
  }

  function handleQueryEnableChange() {
    if (queryCheckbox.checked) {
      queryContainer.style.visibility = '';
      queryContainer.style.position = '';
    } else {
      queryContainer.style.visibility = 'hidden';
      queryContainer.style.position = 'absolute';
    }
    handleQueryChange();
  }

  function treeEditForEditorChange(change) {
    const oldLineCount = change.removed.length;
    const newLineCount = change.text.length;
    const lastLineLength = change.text[newLineCount - 1].length;

    const startPosition = {row: change.from.line, column: change.from.ch};
    const oldEndPosition = {row: change.to.line, column: change.to.ch};
    const newEndPosition = {
      row: startPosition.row + newLineCount - 1,
      column: newLineCount === 1
        ? startPosition.column + lastLineLength
        : lastLineLength
    };

    const startIndex = codeEditor.indexFromPos(change.from);
    let newEndIndex = startIndex + newLineCount - 1;
    let oldEndIndex = startIndex + oldLineCount - 1;
    for (let i = 0; i < newLineCount; i++) newEndIndex += change.text[i].length;
    for (let i = 0; i < oldLineCount; i++) oldEndIndex += change.removed[i].length;

    return {
      startIndex, oldEndIndex, newEndIndex,
      startPosition, oldEndPosition, newEndPosition
    };
  }

  function colorForCaptureName(capture) {
    const id = query.captureNames.indexOf(capture);
    return COLORS_BY_INDEX[id % COLORS_BY_INDEX.length];
  }

  function loadState() {
    const language = localStorage.getItem("language");
    const sourceCode = localStorage.getItem("sourceCode");
    const query = localStorage.getItem("query");
    const queryEnabled = localStorage.getItem("queryEnabled");
    if (language != null && sourceCode != null && query != null) {
      queryInput.value = query;
      codeInput.value = sourceCode;
      languageSelect.value = language;
      queryCheckbox.checked = (queryEnabled === 'true');
    }
  }

  function saveState() {
    localStorage.setItem("language", languageSelect.value);
    localStorage.setItem("sourceCode", codeEditor.getValue());
    saveQueryState();
  }

  function saveQueryState() {
    localStorage.setItem("queryEnabled", queryCheckbox.checked);
    localStorage.setItem("query", queryEditor.getValue());
  }

  function debounce(func, wait, immediate) {
    let timeout;
    return function() {
      const context = this, args = arguments;
      const later = function() {
        timeout = null;
        if (!immediate) func.apply(context, args);
      };
      const callNow = immediate && !timeout;
      clearTimeout(timeout);
      timeout = setTimeout(later, wait);
      if (callNow) func.apply(context, args);
    };
  }
})();
