import type { FuseResultMatch, MatchIndices } from "./core/types";

/**
 * Simple utility to remove HTML tags from a string.
 */
export function stripHtmlTags(html: string): string {
  if (!html) return "";
  return html.replace(/<[^>]*>/g, "").replace("\n", " ");
}

/**
 * Removes HTML tags from a string, but preserves <span class="highlight"> tags.
 */
export function stripHtmlButKeepHighlights(html: string): string {
  if (!html) return "";
  // Use a placeholder for highlight tags, strip others, then restore placeholders.
  const highlightOpenPlaceholder = "__HIGHLIGHT_OPEN__";
  const highlightClosePlaceholder = "__HIGHLIGHT_CLOSE__";

  let processed = html.replace(
    /<span class="highlight">/g,
    highlightOpenPlaceholder,
  );
  processed = processed.replace(/<\/span>/g, (match, offset, fullString) => {
    // Only replace </span> if it likely corresponds to our highlight span
    // This is imperfect but helps avoid replacing unrelated spans.
    // Look backwards for the nearest opening placeholder.
    const lastPlaceholder = fullString.lastIndexOf(
      highlightOpenPlaceholder,
      offset,
    );
    if (lastPlaceholder !== -1) {
      // Check if there's another opening tag between the placeholder and the closing span
      const interveningContent = fullString.substring(
        lastPlaceholder + highlightOpenPlaceholder.length,
        offset,
      );
      if (!/<span/i.test(interveningContent)) {
        return highlightClosePlaceholder;
      }
    }
    return match; // Keep the original </span> if unsure
  });

  // Strip all remaining HTML tags
  processed = processed.replace(/<[^>]*>/g, "");

  // Restore the highlight tags
  processed = processed.replace(
    new RegExp(highlightOpenPlaceholder, "g"),
    '<span class="highlight">',
  );
  processed = processed.replace(
    new RegExp(highlightClosePlaceholder, "g"),
    "</span>",
  );

  return processed;
}

export function highlightMatch(
  text: string,
  term: string,
  matches?: readonly FuseResultMatch[],
): string {
  if (!term.trim() || !matches || matches.length === 0) return text;

  try {
    // Find matches for the text field or allContent that contains the text
    const fieldMatches = matches.find(
      (match) =>
        match.key === "text" ||
        (match.key === "allContent" && match.value?.includes(text)),
    );

    if (
      !fieldMatches ||
      !fieldMatches.indices ||
      fieldMatches.indices.length === 0
    ) {
      return text;
    }

    // Create a map of character positions to mark which ones need highlighting
    const highlightMap = new Array(text.length).fill(false);

    fieldMatches.indices.forEach((indices: MatchIndices) => {
      const start = indices[0];
      const end = indices[1];

      if (fieldMatches.key === "allContent") {
        // Find where our text appears in the allContent
        const allContent = fieldMatches.value;
        const textPos = allContent?.indexOf(text) ?? -1;

        // Only highlight if the match overlaps with our text
        if (textPos >= 0) {
          // Adjust start and end to be relative to our text field
          const relStart = start - textPos;
          const relEnd = end - textPos;

          // Only highlight if the match actually overlaps with our text field
          if (relEnd >= 0 && relStart < text.length) {
            // Mark the overlapping characters
            for (
              let i = Math.max(0, relStart);
              i <= Math.min(text.length - 1, relEnd);
              i++
            ) {
              highlightMap[i] = true;
            }
          }
        }
      } else {
        // Regular text field match - ensure indices are within bounds
        if (start >= 0 && end < text.length) {
          for (let i = start; i <= end; i++) {
            highlightMap[i] = true;
          }
        }
      }
    });

    let result = "";
    let inHighlight = false;

    for (let i = 0; i < text.length; i++) {
      if (highlightMap[i] && !inHighlight) {
        result += '<span class="highlight">';
        inHighlight = true;
      } else if (!highlightMap[i] && inHighlight) {
        result += "</span>";
        inHighlight = false;
      }

      result += text.charAt(i);
    }

    if (inHighlight) {
      result += "</span>";
    }

    return result;
  } catch (e) {
    console.error("Error highlighting match:", e);
    return text;
  }
}

// Function to extract and highlight content snippet using Fuse matches
export function highlightSnippet(
  content: string,
  term: string,
  matches?: readonly FuseResultMatch[],
): string {
  if (!content || !term.trim() || !matches || matches.length === 0)
    return content;

  try {
    // Find matches for content field or allContent that contains the content
    const contentMatches = matches.find(
      (match) =>
        match.key === "content" ||
        (match.key === "allContent" && match.value?.includes(content)),
    );

    if (
      !contentMatches ||
      !contentMatches.indices ||
      contentMatches.indices.length === 0
    ) {
      // No content matches, return plain content
      return content.length > 100 ? content.substring(0, 100) + "..." : content;
    }

    // Find the match indices
    let allIndices: MatchIndices[] = contentMatches.indices as MatchIndices[];

    // If matching against allContent, adjust indices to be relative to content
    if (contentMatches.key === "allContent") {
      const allContent = contentMatches.value;
      const contentPos = allContent?.indexOf(content) ?? -1;

      if (contentPos >= 0) {
        // Adjust indices to be relative to the content field
        allIndices = allIndices
          .map(
            (indices) =>
              [
                indices[0] - contentPos,
                indices[1] - contentPos,
              ] as MatchIndices,
          )
          .filter((indices) => indices[1] >= 0 && indices[0] < content.length);
      }
    }

    if (allIndices.length === 0) {
      return content.length > 100 ? content.substring(0, 100) + "..." : content;
    }

    // Find a good center point for our snippet (average of first match)
    const firstMatch = allIndices[0];
    const matchCenter = Math.floor((firstMatch[0] + firstMatch[1]) / 2);

    // Extract a window around the match
    const windowSize = 100;
    const start = Math.max(0, matchCenter - windowSize / 2);
    const end = Math.min(content.length, matchCenter + windowSize / 2);

    // Create the basic snippet
    let snippet = content.substring(start, end);
    if (start > 0) snippet = "..." + snippet;
    if (end < content.length) snippet += "...";

    // Create a highlighting map for the snippet
    const snippetLength = snippet.length;
    const highlightMap = new Array(snippetLength).fill(false);

    // Calculate offset for the highlighting
    const startOffset = start > 0 ? start - 3 : start; // Account for '...' if present

    // Mark each matched character in the snippet
    allIndices.forEach((indices: MatchIndices) => {
      const matchStart = indices[0];
      const matchEnd = indices[1];

      // Skip matches outside our snippet window
      if (matchEnd < start || matchStart > end) return;

      // Adjust match indices to be relative to snippet
      const snippetMatchStart = Math.max(0, matchStart - startOffset);
      const snippetMatchEnd = Math.min(
        snippetLength - 1,
        matchEnd - startOffset,
      );

      // Mark characters for highlighting
      for (let i = snippetMatchStart; i <= snippetMatchEnd; i++) {
        if (i >= 0 && i < snippetLength) {
          highlightMap[i] = true;
        }
      }
    });

    // Build the highlighted snippet
    let result = "";
    let inHighlight = false;

    for (let i = 0; i < snippetLength; i++) {
      // If highlighting state changes, add appropriate tags
      if (highlightMap[i] && !inHighlight) {
        result += '<span class="highlight">';
        inHighlight = true;
      } else if (!highlightMap[i] && inHighlight) {
        result += "</span>";
        inHighlight = false;
      }

      // Add the current character
      result += snippet.charAt(i);
    }

    // Close highlight tag if we're still in one at the end
    if (inHighlight) {
      result += "</span>";
    }

    return result;
  } catch (e) {
    console.error("Error highlighting snippet:", e);
    return content.length > 100 ? content.substring(0, 100) + "..." : content;
  }
}