import type { ParsedEdge } from "./types";

// Match edge header: allow spaces between '>' characters (Obsidian uses "> >" for nesting)
const EDGE_HEADER_RE = /^\s*((?:>\s*)+)\s*\[!edge\]\s*(.+?)\s*$/i;
// Match edge header WITHOUT leading '>' (plain line) – so edges outside callout blocks are also found
const EDGE_HEADER_PLAIN_RE = /^\s*\[!edge\]\s+(.+?)\s*$/i;
const TARGET_LINK_RE = /\[\[([^\]]+?)\]\]/g;

/** Sentinel: edge block has no quote level (plain lines); only ends on next edge line or end. */
const PLAIN_EDGE_LEVEL = -1;

/**
 * Extract edges from any callout nesting and from plain lines:
 * - Edge with callout: > [!edge] <type> (any number of '>' allowed)
 * - Edge without callout: [!edge] <type> (so edges outside abstract block are found)
 * - Collect targets from subsequent lines while quoteLevel >= edgeLevel (or plain mode)
 * - Stop when:
 *   a) next [!edge] header appears, OR
 *   b) quoteLevel drops below edgeLevel (block ends), ignoring blank lines, OR
 *   c) in plain mode: next [!edge] line
 */
export function parseEdgesFromCallouts(markdown: string): ParsedEdge[] {
  const lines = markdown.split(/\r?\n/);
  const edges: ParsedEdge[] = [];

  let current: ParsedEdge | null = null;
  let currentEdgeLevel = 0;

  const getQuoteLevel = (line: string): number => {
    const m = line.match(/^\s*(?:(?:>\s*)+)/);
    if (!m || !m[0]) return 0;
    return (m[0].match(/>/g) || []).length;
  };

  const flush = (endLine: number) => {
    if (!current) return;
    current.lineEnd = endLine;
    if (current.targets.length > 0) edges.push(current);
    current = null;
    currentEdgeLevel = 0;
  };

  for (let i = 0; i < lines.length; i++) {
    const line = lines[i];
    if (line === undefined) continue;

    // Start of a new edge block (with callout quote)
    const edgeMatch = line.match(EDGE_HEADER_RE);
    if (edgeMatch && edgeMatch[1] && edgeMatch[2]) {
      flush(i - 1);
      currentEdgeLevel = (edgeMatch[1].match(/>/g) || []).length;
      current = {
        rawType: edgeMatch[2].trim(),
        targets: [],
        lineStart: i,
        lineEnd: i,
      };
      continue;
    }

    // Start of edge block without '>' (plain line) – e.g. edge written outside abstract block
    const plainMatch = line.match(EDGE_HEADER_PLAIN_RE);
    if (plainMatch && plainMatch[1]) {
      flush(i - 1);
      currentEdgeLevel = PLAIN_EDGE_LEVEL;
      current = {
        rawType: plainMatch[1].trim(),
        targets: [],
        lineStart: i,
        lineEnd: i,
      };
      continue;
    }

    if (!current) continue;

    const trimmed = line.trim();
    const ql = getQuoteLevel(line);

    // In plain mode, only end on next edge line (already handled above); collect [[links]] from any line
    if (currentEdgeLevel === PLAIN_EDGE_LEVEL) {
      TARGET_LINK_RE.lastIndex = 0;
      let m: RegExpExecArray | null;
      while ((m = TARGET_LINK_RE.exec(line)) !== null) {
        if (m[1]) {
          const t = m[1].trim();
          if (t) current.targets.push(t);
        }
      }
      continue;
    }

    // End of quoted edge block if quote level drops below the edge header level
    if (trimmed !== "" && ql < currentEdgeLevel) {
      flush(i - 1);
      continue;
    }

    // Collect targets (multiple per line allowed)
    TARGET_LINK_RE.lastIndex = 0;
    let m: RegExpExecArray | null;
    while ((m = TARGET_LINK_RE.exec(line)) !== null) {
      if (m[1]) {
        const t = m[1].trim();
        if (t) current.targets.push(t);
      }
    }
  }

  flush(lines.length - 1);
  return edges;
}