/*
 * Copyright (C) 2026 Mateusz Gruszczyński @linuxiarz.pl
 * Source-Available Code / Dual-Licensed.
 * 
 * Free for non-commercial and evaluation use under terms of BSL/GPLv3.
 * Commercial or production use requires a valid paid license.
 * See LICENSE file in repository root for details.
 */

function selection(editor) {
  return { start: editor.selectionStart, end: editor.selectionEnd };
}

function toggleWrap(editor, before, after = before, placeholder = "tekst") {
  let { start, end } = selection(editor);
  const value = editor.value;
  const selected = value.slice(start, end);

  if (start >= before.length && value.slice(start - before.length, start) === before && value.slice(end, end + after.length) === after) {
    editor.setRangeText(selected, start - before.length, end + after.length, "select");
    return;
  }
  if (selected.includes("\n") && !before.includes("\n") && !after.includes("\n")) {
    const lines = selected.split("\n");
    const nonEmpty = lines.filter(line => line.length > 0);
    const allWrapped = nonEmpty.length > 0 && nonEmpty.every(line => line.startsWith(before) && line.endsWith(after) && line.length >= before.length + after.length);
    const replacement = lines.map(line => {
      if (!line) return line;
      return allWrapped ? line.slice(before.length, line.length - after.length) : `${before}${line}${after}`;
    }).join("\n");
    editor.setRangeText(replacement, start, end, "select");
    return;
  }

  if (selected.startsWith(before) && selected.endsWith(after) && selected.length >= before.length + after.length) {
    editor.setRangeText(selected.slice(before.length, -after.length), start, end, "select");
    return;
  }

  const text = selected || placeholder;
  editor.setRangeText(before + text + after, start, end, "select");
  if (!selected) editor.setSelectionRange(start + before.length, start + before.length + text.length);
}

function togglePrefix(editor, prefixFactory) {
  const { start, end } = selection(editor);
  const lineStart = editor.value.lastIndexOf("\n", start - 1) + 1;
  const selected = editor.value.slice(lineStart, end);
  const lines = selected.split("\n");
  const prefixes = lines.map((_, index) => typeof prefixFactory === "function" ? prefixFactory(index) : prefixFactory);
  const allPrefixed = lines.every((line, index) => line.startsWith(prefixes[index]));
  const replacement = lines.map((line, index) => allPrefixed ? line.slice(prefixes[index].length) : prefixes[index] + line).join("\n");
  editor.setRangeText(replacement, lineStart, end, "select");
}

export function applyFormat(editor, format) {
  if (format === "bold") toggleWrap(editor, "**");
  if (format === "italic") toggleWrap(editor, "*");
  if (format === "strike") toggleWrap(editor, "~~");
  if (format === "heading" || format === "heading2") togglePrefix(editor, "## ");
  if (format === "heading1") togglePrefix(editor, "# ");
  if (format === "heading3") togglePrefix(editor, "### ");
  if (format === "heading4") togglePrefix(editor, "#### ");
  if (format === "bullet") togglePrefix(editor, "- ");
  if (format === "number") togglePrefix(editor, index => `${index + 1}. `);
  if (format === "task") togglePrefix(editor, "- [ ] ");
  if (format === "quote") togglePrefix(editor, "> ");
  if (format === "link") toggleWrap(editor, "[", "](https://)", "description");
  if (format === "inline-code") toggleWrap(editor, "`", "`", "code");
  if (format === "highlight") toggleWrap(editor, "==", "==", "important");
  if (format === "subscript") toggleWrap(editor, "~", "~", "2");
  if (format === "superscript") toggleWrap(editor, "^", "^", "2");
  if (format === "codeblock") toggleWrap(editor, "```text\n", "\n```", "code");
  if (format === "codeblock-lines") toggleWrap(editor, "```text=\n", "\n```", "code");
  if (format === "mermaid") toggleWrap(editor, "```mermaid\n", "\n```", "graph TD\n  A[Start] --> B[End]");
  if (format === "details") toggleWrap(editor, "<details>\n<summary>Click me</summary>\n\n", "\n</details>", "Content");
  if (format === "toc") {
    const { start, end } = selection(editor);
    const selected = editor.value.slice(start, end);
    editor.setRangeText(selected || "[TOC]", start, end, selected ? "select" : "end");
  }
  if (format.startsWith("alert-")) {
    const type = format.slice("alert-".length);
    toggleWrap(editor, `:::${type}\n`, "\n:::", "Alert content");
  }
  if (format === "table") toggleWrap(editor, "| Column 1 | Column 2 |\n| --- | --- |\n| ", " | value |", "value");
  if (format === "footnote") toggleWrap(editor, "", "[^1]\n\n[^1]: Footnote text", "Text with footnote");
  if (format === "definition") toggleWrap(editor, "", "\n: Definition", "Term");
  if (format === "horizontal-rule") toggleWrap(editor, "\n---\n", "", "");
  editor.focus();
  editor.dispatchEvent(new Event("input", { bubbles: true }));
}

export function bindFormatShortcuts(editor) {
  editor.addEventListener("keydown", event => {
    const primary = event.ctrlKey || event.metaKey;
    let format = null;
    if (primary && !event.shiftKey && event.key.toLowerCase() === "z") return; // native textarea undo
    if (primary && !event.shiftKey && event.key.toLowerCase() === "b") format = "bold";
    else if (primary && !event.shiftKey && event.key.toLowerCase() === "i") format = "italic";
    else if (primary && event.shiftKey && event.key.toLowerCase() === "x") format = "strike";
    else if (primary && !event.shiftKey && event.key.toLowerCase() === "k") format = "link";
    else if (primary && event.shiftKey && event.key === "7") format = "number";
    else if (primary && event.shiftKey && event.key === "8") format = "bullet";
    else if (primary && event.shiftKey && event.key === "9") format = "task";
    else if (event.altKey && /^[1-4]$/.test(event.key)) format = `heading${event.key}`;
    if (!format) return;
    event.preventDefault();
    applyFormat(editor, format);
  });
}

function selectedLineRange(value, start, end) {
  const blockStart = value.lastIndexOf("\n", Math.max(0, start - 1)) + 1;
  let blockEnd = value.indexOf("\n", end);
  if (blockEnd < 0) blockEnd = value.length;
  if (end > start && value[end - 1] === "\n") blockEnd = end - 1;
  return { blockStart, blockEnd };
}

function mapOffsetThroughEdits(offset, edits) {
  let delta = 0;
  for (const edit of edits) {
    if (offset < edit.start) break;
    const editEnd = edit.start + edit.remove;
    if (offset <= editEnd) return edit.start + delta + edit.insert.length;
    delta += edit.insert.length - edit.remove;
  }
  return offset + delta;
}

export function applyIndentation(editor, { outdent = false, size = 2 } = {}) {
  if (!editor || editor.readOnly) return false;
  const indent = " ".repeat(Math.max(1, Number(size) || 2));
  const start = editor.selectionStart;
  const end = editor.selectionEnd;
  const direction = editor.selectionDirection || "none";

  if (!outdent && start === end) {
    editor.setRangeText(indent, start, end, "end");
    editor.dispatchEvent(new Event("input", { bubbles: true }));
    return true;
  }

  const value = editor.value;
  const { blockStart, blockEnd } = selectedLineRange(value, start, end);
  const block = value.slice(blockStart, blockEnd);
  const lineStarts = [0];
  for (let index = 0; index < block.length; index++) {
    if (block[index] === "\n") lineStarts.push(index + 1);
  }

  const edits = lineStarts.map(relativeStart => {
    const absoluteStart = blockStart + relativeStart;
    if (!outdent) return { start: absoluteStart, remove: 0, insert: indent };
    const line = value.slice(absoluteStart, value.indexOf("\n", absoluteStart) < 0 ? value.length : value.indexOf("\n", absoluteStart));
    const removable = line.startsWith("\t") ? 1 : Math.min(indent.length, (line.match(/^ +/) || [""])[0].length);
    return { start: absoluteStart, remove: removable, insert: "" };
  }).filter(edit => edit.remove || edit.insert);

  if (!edits.length) return false;
  let replacement = block;
  for (let index = edits.length - 1; index >= 0; index--) {
    const edit = edits[index];
    const relativeStart = edit.start - blockStart;
    replacement = `${replacement.slice(0, relativeStart)}${edit.insert}${replacement.slice(relativeStart + edit.remove)}`;
  }

  const nextStart = mapOffsetThroughEdits(start, edits);
  const nextEnd = mapOffsetThroughEdits(end, edits);
  editor.setRangeText(replacement, blockStart, blockEnd, "start");
  editor.setSelectionRange(nextStart, nextEnd, direction);
  editor.dispatchEvent(new Event("input", { bubbles: true }));
  return true;
}

export function bindIndentationShortcuts(editor, { size = 2 } = {}) {
  editor.addEventListener("keydown", event => {
    if (event.key !== "Tab" || event.ctrlKey || event.metaKey || event.altKey) return;
    if (editor.readOnly) return;
    event.preventDefault();
    applyIndentation(editor, { outdent: event.shiftKey, size });
  });
}