// richtext.js - Shared richtext parsing and rendering for tools.slices.network

/**
 * Helper functions for consistent facet type detection.
 * Handles both $type (stored facets) and __typename (GraphQL responses).
 */
export function isFacetType(type, facetType) {
  if (!type) return false;
  const normalized = type.toLowerCase();
  return normalized.includes(facetType.toLowerCase());
}

export const FacetTypes = {
  isLink: (type) => isFacetType(type, 'link'),
  isBold: (type) => isFacetType(type, 'bold'),
  isItalic: (type) => isFacetType(type, 'italic'),
  isCode: (type) => isFacetType(type, 'code') && !isFacetType(type, 'codeblock'),
  isCodeBlock: (type) => isFacetType(type, 'codeblock'),
};

export const BlockTypes = {
  isParagraph: (type) => isFacetType(type, 'paragraph'),
  isHeading: (type) => isFacetType(type, 'heading'),
  isCodeBlock: (type) => isFacetType(type, 'codeblock'),
  isQuote: (type) => isFacetType(type, 'quote'),
  isTangledEmbed: (type) => isFacetType(type, 'tangledembed'),
  isImageEmbed: (type) => isFacetType(type, 'imageembed'),
};

/**
 * Parse markdown-style text into facets for AT Protocol storage.
 * Detects: code blocks, bold, italic, inline code, URLs
 * Returns { text, facets } where text preserves delimiters for editing.
 */
export function parseFacets(text) {
  if (!text) return { text: "", facets: [] };

  const facets = [];
  const encoder = new TextEncoder();

  // Track which character positions are already claimed by a facet
  const claimedPositions = new Set();

  // Helper to check if a range overlaps with claimed positions
  function isRangeClaimed(start, end) {
    for (let i = start; i < end; i++) {
      if (claimedPositions.has(i)) return true;
    }
    return false;
  }

  // Helper to claim a range
  function claimRange(start, end) {
    for (let i = start; i < end; i++) {
      claimedPositions.add(i);
    }
  }

  // Helper to get byte offset for a character position
  function getByteOffset(str, charIndex) {
    return encoder.encode(str.slice(0, charIndex)).length;
  }

  // Process code blocks FIRST (highest priority) - they should not be parsed for other patterns
  const codeBlockRegex = /```(\w*)\n([\s\S]*?)```/g;
  let codeBlockMatch;
  while ((codeBlockMatch = codeBlockRegex.exec(text)) !== null) {
    const start = codeBlockMatch.index;
    const end = start + codeBlockMatch[0].length;

    if (!isRangeClaimed(start, end)) {
      claimRange(start, end);
      const lang = codeBlockMatch[1] || undefined;
      facets.push({
        index: {
          byteStart: getByteOffset(text, start),
          byteEnd: getByteOffset(text, end),
        },
        features: [
          {
            $type: "network.slices.tools.richtext.facet#codeBlock",
            lang,
          },
        ],
      });
    }
  }

  // Bold: **text**
  const boldRegex = /\*\*(.+?)\*\*/g;
  let boldMatch;
  while ((boldMatch = boldRegex.exec(text)) !== null) {
    const start = boldMatch.index;
    const end = start + boldMatch[0].length;

    if (!isRangeClaimed(start, end)) {
      claimRange(start, end);
      facets.push({
        index: {
          byteStart: getByteOffset(text, start),
          byteEnd: getByteOffset(text, end),
        },
        features: [{ $type: "network.slices.tools.richtext.facet#bold" }],
      });
    }
  }

  // Italic: *text* or _text_ (but not inside bold)
  const italicRegex = /(?<!\*)\*([^*]+)\*(?!\*)|_([^_]+)_/g;
  let italicMatch;
  while ((italicMatch = italicRegex.exec(text)) !== null) {
    const start = italicMatch.index;
    const end = start + italicMatch[0].length;

    if (!isRangeClaimed(start, end)) {
      claimRange(start, end);
      facets.push({
        index: {
          byteStart: getByteOffset(text, start),
          byteEnd: getByteOffset(text, end),
        },
        features: [{ $type: "network.slices.tools.richtext.facet#italic" }],
      });
    }
  }

  // Inline code: `code`
  const codeRegex = /`([^`]+)`/g;
  let codeMatch;
  while ((codeMatch = codeRegex.exec(text)) !== null) {
    const start = codeMatch.index;
    const end = start + codeMatch[0].length;

    if (!isRangeClaimed(start, end)) {
      claimRange(start, end);
      facets.push({
        index: {
          byteStart: getByteOffset(text, start),
          byteEnd: getByteOffset(text, end),
        },
        features: [{ $type: "network.slices.tools.richtext.facet#code" }],
      });
    }
  }

  // URLs
  const urlRegex = /https?:\/\/[^\s<>\[\]()]+/g;
  let urlMatch;
  while ((urlMatch = urlRegex.exec(text)) !== null) {
    const start = urlMatch.index;
    const end = start + urlMatch[0].length;

    if (!isRangeClaimed(start, end)) {
      claimRange(start, end);
      facets.push({
        index: {
          byteStart: getByteOffset(text, start),
          byteEnd: getByteOffset(text, end),
        },
        features: [
          {
            $type: "network.slices.tools.richtext.facet#link",
            uri: urlMatch[0],
          },
        ],
      });
    }
  }

  // Sort facets by byte position
  facets.sort((a, b) => a.index.byteStart - b.index.byteStart);

  return { text, facets };
}

/**
 * Render faceted text as HTML.
 * Falls back to parseFacets if no facets provided (legacy content).
 * Strips markdown delimiters for display.
 */
export function renderFacetedText(text, facets, options = {}) {
  if (!text) return "";

  const { escapeHtml = defaultEscapeHtml } = options;

  // If no facets provided, parse on the fly (legacy support)
  if (!facets || facets.length === 0) {
    const parsed = parseFacets(text);
    facets = parsed.facets;
  }

  if (facets.length === 0) {
    return escapeHtml(text);
  }

  const encoder = new TextEncoder();
  const decoder = new TextDecoder();
  const bytes = encoder.encode(text);

  // Sort facets by start position
  const sortedFacets = [...facets].sort(
    (a, b) => a.index.byteStart - b.index.byteStart
  );

  let result = "";
  let lastEnd = 0;

  for (const facet of sortedFacets) {
    // Add text before this facet
    if (facet.index.byteStart > lastEnd) {
      const beforeBytes = bytes.slice(lastEnd, facet.index.byteStart);
      result += escapeHtml(decoder.decode(beforeBytes));
    }

    // Get the faceted text
    const facetBytes = bytes.slice(facet.index.byteStart, facet.index.byteEnd);
    let facetText = decoder.decode(facetBytes);

    // Determine facet type and render
    const feature = facet.features[0];
    const type = feature?.$type || feature?.__typename || "";

    if (FacetTypes.isLink(type)) {
      const uri = feature.uri;
      result += `<a href="${escapeHtml(uri)}" target="_blank" rel="noopener" class="facet-link">${escapeHtml(facetText)}</a>`;
    } else if (FacetTypes.isBold(type)) {
      // Strip ** delimiters
      const content = facetText.replace(/^\*\*|\*\*$/g, "");
      result += `<strong class="facet-bold">${escapeHtml(content)}</strong>`;
    } else if (FacetTypes.isItalic(type)) {
      // Strip * or _ delimiters
      const content = facetText.replace(/^\*|\*$|^_|_$/g, "");
      result += `<em class="facet-italic">${escapeHtml(content)}</em>`;
    } else if (FacetTypes.isCodeBlock(type)) {
      // Strip ``` delimiters and extract content
      const match = facetText.match(/^```(\w*)\n([\s\S]*?)```$/);
      if (match) {
        const lang = match[1] || "";
        const code = match[2];
        const langClass = lang ? ` language-${escapeHtml(lang)}` : "";
        result += `<pre class="facet-codeblock${langClass}"><code>${escapeHtml(code)}</code></pre>`;
      } else {
        result += `<pre class="facet-codeblock"><code>${escapeHtml(facetText)}</code></pre>`;
      }
    } else if (FacetTypes.isCode(type)) {
      // Strip ` delimiters
      const content = facetText.replace(/^`|`$/g, "");
      result += `<code class="facet-code">${escapeHtml(content)}</code>`;
    } else {
      result += escapeHtml(facetText);
    }

    lastEnd = facet.index.byteEnd;
  }

  // Add remaining text
  if (lastEnd < bytes.length) {
    const remainingBytes = bytes.slice(lastEnd);
    result += escapeHtml(decoder.decode(remainingBytes));
  }

  return result;
}

/**
 * Convert text + facets to HTML for contenteditable editing.
 * Returns HTML string with formatting tags.
 */
export function facetsToDom(text, facets = []) {
  if (!text) return "";

  if (!facets || facets.length === 0) {
    return escapeHtmlForDom(text);
  }

  const encoder = new TextEncoder();
  const decoder = new TextDecoder();
  const bytes = encoder.encode(text);

  // Sort facets by start position
  const sortedFacets = [...facets].sort(
    (a, b) => a.index.byteStart - b.index.byteStart
  );

  let result = "";
  let lastEnd = 0;

  for (const facet of sortedFacets) {
    // Add text before this facet
    if (facet.index.byteStart > lastEnd) {
      const beforeBytes = bytes.slice(lastEnd, facet.index.byteStart);
      result += escapeHtmlForDom(decoder.decode(beforeBytes));
    }

    // Get the faceted text
    const facetBytes = bytes.slice(facet.index.byteStart, facet.index.byteEnd);
    const facetText = decoder.decode(facetBytes);

    // Determine facet type and wrap in tag
    const feature = facet.features[0];
    const type = feature?.$type || feature?.__typename || "";

    if (FacetTypes.isLink(type)) {
      result += `<a href="${escapeHtmlForDom(feature.uri)}" class="facet-link">${escapeHtmlForDom(facetText)}</a>`;
    } else if (FacetTypes.isBold(type)) {
      result += `<strong>${escapeHtmlForDom(facetText)}</strong>`;
    } else if (FacetTypes.isItalic(type)) {
      result += `<em>${escapeHtmlForDom(facetText)}</em>`;
    } else if (FacetTypes.isCode(type)) {
      result += `<code>${escapeHtmlForDom(facetText)}</code>`;
    } else {
      result += escapeHtmlForDom(facetText);
    }

    lastEnd = facet.index.byteEnd;
  }

  // Add remaining text
  if (lastEnd < bytes.length) {
    const remainingBytes = bytes.slice(lastEnd);
    result += escapeHtmlForDom(decoder.decode(remainingBytes));
  }

  return result;
}

function escapeHtmlForDom(text) {
  return text
    .replace(/&/g, "&amp;")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
    .replace(/"/g, "&quot;");
}

/**
 * Extract text and facets from a contenteditable element.
 * Walks the DOM tree and builds facets from formatting tags.
 * Returns { text, facets }.
 */
export function domToFacets(element) {
  const encoder = new TextEncoder();
  let text = "";
  const facets = [];

  function walk(node, activeFormats = []) {
    if (node.nodeType === Node.TEXT_NODE) {
      const content = node.textContent || "";
      if (content) {
        const startByte = encoder.encode(text).length;
        text += content;
        const endByte = encoder.encode(text).length;

        // Create facets for each active format
        for (const format of activeFormats) {
          facets.push({
            index: { byteStart: startByte, byteEnd: endByte },
            features: [format],
          });
        }
      }
    } else if (node.nodeType === Node.ELEMENT_NODE) {
      const tag = node.tagName.toLowerCase();
      let newFormat = null;

      if (tag === "strong" || tag === "b") {
        newFormat = { $type: "network.slices.tools.richtext.facet#bold" };
      } else if (tag === "em" || tag === "i") {
        newFormat = { $type: "network.slices.tools.richtext.facet#italic" };
      } else if (tag === "code") {
        newFormat = { $type: "network.slices.tools.richtext.facet#code" };
      } else if (tag === "a") {
        newFormat = {
          $type: "network.slices.tools.richtext.facet#link",
          uri: node.getAttribute("href") || "",
        };
      }

      const formats = newFormat ? [...activeFormats, newFormat] : activeFormats;

      for (const child of node.childNodes) {
        walk(child, formats);
      }
    }
  }

  walk(element);

  // Merge adjacent facets of the same type
  const mergedFacets = mergeFacets(facets);

  // Detect URLs in plain text that aren't already linked or in code
  const urlRegex = /https?:\/\/[^\s<>\[\]()]+/g;
  let urlMatch;
  while ((urlMatch = urlRegex.exec(text)) !== null) {
    const startByte = encoder.encode(text.slice(0, urlMatch.index)).length;
    const endByte = encoder.encode(text.slice(0, urlMatch.index + urlMatch[0].length)).length;

    // Check if this range is already covered by a link or code facet
    const alreadyCovered = mergedFacets.some(f => {
      const type = f.features[0]?.$type || '';
      return (FacetTypes.isLink(type) || FacetTypes.isCode(type)) &&
             f.index.byteStart <= startByte && f.index.byteEnd >= endByte;
    });

    if (!alreadyCovered) {
      mergedFacets.push({
        index: { byteStart: startByte, byteEnd: endByte },
        features: [{
          $type: "network.slices.tools.richtext.facet#link",
          uri: urlMatch[0],
        }],
      });
    }
  }

  // Re-sort after adding URL facets
  mergedFacets.sort((a, b) => a.index.byteStart - b.index.byteStart);

  return { text, facets: mergedFacets };
}

/**
 * Merge adjacent facets of the same type.
 */
function mergeFacets(facets) {
  if (facets.length === 0) return [];

  // Group by type
  const byType = new Map();
  for (const facet of facets) {
    const type = facet.features[0]?.$type || "";
    const key = type + (facet.features[0]?.uri || "");
    if (!byType.has(key)) {
      byType.set(key, []);
    }
    byType.get(key).push(facet);
  }

  const merged = [];
  for (const group of byType.values()) {
    // Sort by start position
    group.sort((a, b) => a.index.byteStart - b.index.byteStart);

    let current = null;
    for (const facet of group) {
      if (!current) {
        current = { ...facet, index: { ...facet.index } };
      } else if (facet.index.byteStart <= current.index.byteEnd) {
        // Merge overlapping or adjacent
        current.index.byteEnd = Math.max(current.index.byteEnd, facet.index.byteEnd);
      } else {
        merged.push(current);
        current = { ...facet, index: { ...facet.index } };
      }
    }
    if (current) {
      merged.push(current);
    }
  }

  // Sort by start position
  merged.sort((a, b) => a.index.byteStart - b.index.byteStart);

  return merged;
}

/**
 * Default HTML escape function.
 */
function defaultEscapeHtml(text) {
  return text
    .replace(/&/g, "&amp;")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
    .replace(/"/g, "&quot;")
    .replace(/'/g, "&#039;");
}