/**
 * Helper functions for unresolved link detection and handling.
 */

import { App, TFile } from "obsidian";

/**
 * Normalize heading string for comparison only (Inspect Chains / Chain Workbench).
 * Maps "Überschrift", "Überschrift ^Block", "Überschrift Block" to the same canonical form
 * so that Obsidian UI links (no ^) and plugin/sectionParser variants match.
 * - Strip trailing block-id with caret: \s+\^[a-zA-Z0-9_-]+$
 * - Strip one trailing word (Obsidian stores "Überschrift Block" without ^)
 * Use only for equality checks, not for display or stored links.
 */
export function normalizeHeadingForMatch(heading: string | null): string | null {
  if (heading === null || heading === undefined) return null;
  let s = heading.trim();
  if (!s) return null;
  // 1) Remove optional block-id suffix with caret: "Überschrift ^Block" -> "Überschrift"
  s = s.replace(/\s+\^[a-zA-Z0-9_-]+\s*$/, "").trim();
  // 2) Remove one trailing word (Obsidian link form "Überschrift Block" -> "Überschrift")
  s = s.replace(/\s+[a-zA-Z0-9_-]+\s*$/, "").trim();
  return s || null;
}

/**
 * Compare two headings for equality using normalized form (block-id suffix and trailing word stripped).
 * Use for Inspect Chains / Chain Workbench matching only.
 */
export function headingsMatch(a: string | null, b: string | null): boolean {
  const na = normalizeHeadingForMatch(a);
  const nb = normalizeHeadingForMatch(b);
  if (na === null && nb === null) return true;
  if (na === null || nb === null) return false;
  return na === nb;
}

/**
 * Normalize link target by removing alias separator (|) and heading separator (#).
 * Preserves spaces and case.
 * Examples:
 * - "file#sec|alias" -> "file"
 * - "My Note" -> "My Note"
 * - "My Note|Display" -> "My Note"
 */
export function normalizeLinkTarget(raw: string): string {
  if (!raw) return "";
  
  // Split by pipe (alias separator) and take first part
  const parts = raw.split("|");
  const firstPart = parts[0];
  if (!firstPart) return raw.trim();
  
  // Split by hash (heading separator) and take first part
  const baseParts = firstPart.split("#");
  const base = baseParts[0];
  if (!base) return raw.trim();
  
  return base.trim();
}

/**
 * Extract link target from an anchor element.
 * Prefers data-href attribute, falls back to textContent.
 * Returns normalized target (without alias/heading).
 */
export function extractLinkTargetFromAnchor(anchor: HTMLElement): string | null {
  const dataHref = anchor.getAttribute("data-href");
  const textContent = anchor.textContent;
  
  // Try data-href first
  if (dataHref) {
    return normalizeLinkTarget(dataHref);
  }
  
  // Fall back to text content
  if (textContent) {
    return normalizeLinkTarget(textContent.trim());
  }
  
  return null;
}

/**
 * Check if a link target is unresolved (file doesn't exist).
 * Uses metadataCache as single source of truth.
 */
export function isUnresolvedLink(
  app: App,
  target: string,
  sourcePath: string
): boolean {
  if (!target) return false;
  
  const resolvedFile = app.metadataCache.getFirstLinkpathDest(target, sourcePath);
  return resolvedFile === null;
}

/**
 * Parse wikilink at cursor position in a line of text.
 * Finds the nearest [[...]] that contains or is near the cursor position.
 * Returns the raw target (with alias/heading) or null if not found.
 */
export function parseWikilinkAtPosition(
  lineText: string,
  cursorPosInLine: number
): string | null {
  if (!lineText || cursorPosInLine < 0) return null;

  // Find all [[...]] pairs in the line
  const linkPattern = /\[\[([^\]]+)\]\]/g;
  const matches: Array<{ start: number; end: number; target: string }> = [];
  let match;

  while ((match = linkPattern.exec(lineText)) !== null) {
    const start = match.index;
    const end = match.index + match[0].length;
    const target = match[1]; // Content between [[ and ]]
    
    if (target) {
      matches.push({ start, end, target });
    }
  }

  if (matches.length === 0) return null;

  // Find the link that contains the cursor or is closest to it
  for (const link of matches) {
    if (cursorPosInLine >= link.start && cursorPosInLine <= link.end) {
      // Cursor is inside this link
      return link.target;
    }
  }

  // If cursor is not inside any link, find the nearest one
  let nearestLink: { start: number; end: number; target: string } | null = null;
  let minDistance = Infinity;

  for (const link of matches) {
    // Distance to link start or end, whichever is closer
    const distToStart = Math.abs(cursorPosInLine - link.start);
    const distToEnd = Math.abs(cursorPosInLine - link.end);
    const distance = Math.min(distToStart, distToEnd);

    if (distance < minDistance) {
      minDistance = distance;
      nearestLink = link;
    }
  }

  // Only return if reasonably close (e.g., within 10 characters)
  if (nearestLink && minDistance <= 10) {
    return nearestLink.target;
  }

  return null;
}

/**
 * Wait for a file to be modified after creation, or timeout.
 * Returns "modified" if modify event fired, "timeout" otherwise.
 * Useful for Templater compatibility.
 */
export function waitForFileModify(
  app: App,
  file: TFile,
  timeoutMs: number
): Promise<"modified" | "timeout"> {
  return new Promise((resolve) => {
    let resolved = false;
    
    const timeout = setTimeout(() => {
      if (!resolved) {
        resolved = true;
        app.vault.off("modify", handler);
        resolve("timeout");
      }
    }, timeoutMs);
    
    const handler = (modifiedFile: TFile) => {
      if (modifiedFile.path === file.path && !resolved) {
        resolved = true;
        clearTimeout(timeout);
        app.vault.off("modify", handler);
        resolve("modified");
      }
    };
    
    app.vault.on("modify", handler);
  });
}