/**
 * Markdown preprocess — deterministic transforms for Feishu doc creation.
 *
 * Handles:
 * - Blue numbering prefix on numbered headings
 * - Heading background color via block-level PATCH (not in this module)
 * - Rainbow color mapping per heading level
 * - Inline text color/bg via Lark-flavored markdown
 */

import { readFileSync, writeFileSync } from "node:fs";

// ─── Types ──────────────────────────────────────────────────────────────

export interface RainbowConfig {
  /** Number prefix color */
  numberColor: string;
  /** Background color name for <text bgcolor="..."> */
  bgColor: string;
}

export interface PreprocessOptions {
  /** Rainbow color map per heading level (2=##, 3=###, etc.) */
  rainbowMap?: Record<number, RainbowConfig>;
  /** Strip first H1 if it duplicates the document title */
  stripTitle?: boolean;
  /** Number prefix color (used when no rainbow map) */
  numberColor?: string;
}

// ─── Defaults ───────────────────────────────────────────────────────────

const DEFAULT_RAINBOW: Record<number, RainbowConfig> = {
  2: { numberColor: "blue", bgColor: "light-orange" },
  3: { numberColor: "blue", bgColor: "light-yellow" },
  4: { numberColor: "blue", bgColor: "light-green" },
  5: { numberColor: "blue", bgColor: "light-blue" },
  6: { numberColor: "blue", bgColor: "light-yellow" },
};

// ─── Regex ──────────────────────────────────────────────────────────────

const HEADING_RE = /^(#{1,9})\s+(.*)$/;
// Matches: 1. Title | 1.1 Background | 1.1.1 Scope | 2) Title
const NUMBER_PREFIX_RE = /^(?<num>\d+(?:\.\d+)*(?:\.|\))?)\s+(?<title>.+?)\s*$/;
// Detects already-decorated headings
const TEXT_TAG_RE = /^<text\s+[^>]+>/i;
// Matches {color="..."} heading attributes
const HEADING_BG_ATTR_RE = /\s*\{color="[^"]*(?:Background)?"(?:\s+align="[^"]*")?\}/gi;

// ─── Core ───────────────────────────────────────────────────────────────

/**
 * Transform a single heading line.
 * - Plain numbered heading → blue prefix + optional rainbow bg
 * - Already decorated → pass through
 * - No number → bg only
 */
export function transformHeading(
  line: string,
  rainbowMap: Record<number, RainbowConfig> = DEFAULT_RAINBOW
): string {
  const m = HEADING_RE.exec(line);
  if (!m) return line;

  const [, hashes, rawContent] = m;
  const content = rawContent.trimEnd();

  // Already has <text> tag — leave unchanged
  if (TEXT_TAG_RE.test(content)) return line;

  const level = hashes.length;
  const colors =
    rainbowMap[level] ?? rainbowMap[2] ?? { numberColor: "blue", bgColor: "light-orange" };

  // Remove old {color=...} heading attributes
  const clean = content.replace(HEADING_BG_ATTR_RE, "").trim();

  const nm = NUMBER_PREFIX_RE.exec(clean);
  if (!nm?.groups) {
    // No number — just pass through, block-level bg handled by PATCH
    return `${hashes} ${clean}`;
  }

  let number = nm.groups.num;
  const title = nm.groups.title;

  // Normalize: "1" → "1.", "1." → "1" (strip trailing dot for multi-level)
  if (!number.includes(".") && /\d$/.test(number)) {
    number = number + ".";
  } else if (number.endsWith(".")) {
    number = number.slice(0, -1);
  }

  // Blue number prefix only — block-level bg handled by PATCH
  return `${hashes} <text color="${colors.numberColor}">${number} </text>${title}`;
}

/**
 * Preprocess full markdown text.
 */
export function preprocessMarkdown(
  text: string,
  opts: PreprocessOptions = {}
): string {
  const rainbowMap = opts.rainbowMap ?? DEFAULT_RAINBOW;
  let lines = text.split("\n");

  // Optionally strip first H1
  if (opts.stripTitle && lines[0]?.startsWith("# ")) {
    lines = lines.slice(1);
    if (lines[0] === "") lines = lines.slice(1);
  }

  // Build set of lines inside code blocks or lark-table blocks to exclude from heading detection
  const excludedLines = new Set<number>();
  let insideCode = false;
  let insideLarkTable = false;
  for (let i = 0; i < lines.length; i++) {
    const trimmed = lines[i].trim();

    if (trimmed.startsWith("```")) {
      insideCode = !insideCode;
      excludedLines.add(i);
      continue;
    }

    if (/<lark-table[\s>]/.test(trimmed)) insideLarkTable = true;
    if (insideCode || insideLarkTable) excludedLines.add(i);
    if (/<\/lark-table>/.test(trimmed)) insideLarkTable = false;
  }

  // Scan: count H1 headings to decide numbering start level
  const h1Count = lines.filter((l, i) =>
    !excludedLines.has(i) && /^# (?!#)/.test(l.trim())
  ).length;
  const numberLevel = h1Count <= 1 ? 2 : 1; // single H1 = title, skip it

  // Track heading counter for sequential blue numbering
  let headingCounter = 0;
  const out = lines.map((line, idx) => {
    if (excludedLines.has(idx)) return line;

    // Check BEFORE transformHeading if already has number
    const preTrimmed = line.trim();
    const preHeadingMatch = preTrimmed.match(/^(#{1,6}) (.+)/);
    if (preHeadingMatch) {
      const level = preHeadingMatch[1].length;
      const content = preHeadingMatch[2];
      const numMatch = content.match(/^(\d+)\.?\s/);
      if (numMatch && level === numberLevel) {
        // Update counter to this number, then skip processing
        headingCounter = parseInt(numMatch[1]);
        // Still apply transformHeading for other formatting
        return transformHeading(line, rainbowMap);
      }
    }

    const transformed = transformHeading(line, rainbowMap);
    const trimmed = transformed.trim();
    // Skip if already has <text> tag
    if (/^#{1,6} <text/.test(trimmed)) return transformed;

    const headingMatch = trimmed.match(/^(#{1,6}) (.+)/);
    if (headingMatch) {
      const level = headingMatch[1].length;

      if (level === numberLevel) {
        headingCounter++;
        const colors = rainbowMap[level] ?? rainbowMap[2] ?? { numberColor: "blue", bgColor: "light-orange" };
        return transformed.replace(
          new RegExp(`^(#{${level}} )(.+)`),
          `$1<text color="${colors.numberColor}">${headingCounter} </text>$2`
        );
      }
    }
    return transformed;
  });
  const trailing = text.endsWith("\n") ? "\n" : "";
  let result = out.join("\n") + trailing;

  // Normalize bold integer bg colors to light variants
  result = result.replaceAll('bgcolor="green"', 'bgcolor="light-green"');
  result = result.replaceAll('bgcolor="blue"', 'bgcolor="light-blue"');
  result = result.replaceAll('bgcolor="orange"', 'bgcolor="light-orange"');
  result = result.replaceAll('bgcolor="yellow"', 'bgcolor="light-yellow"');
  result = result.replaceAll('bgcolor="red"', 'bgcolor="light-red"');
  // Also handle background-color attribute name
  result = result.replaceAll('background-color="green"', 'background-color="light-green"');
  result = result.replaceAll('background-color="blue"', 'background-color="light-blue"');
  result = result.replaceAll('background-color="orange"', 'background-color="light-orange"');
  result = result.replaceAll('background-color="yellow"', 'background-color="light-yellow"');
  result = result.replaceAll('background-color="red"', 'background-color="light-red"');

  return result;
}

// ─── CLI ────────────────────────────────────────────────────────────────

function main() {
  const args = process.argv.slice(2);
  if (args.length === 0) {
    // stdin mode
    const chunks: Buffer[] = [];
    process.stdin.on("data", (c: Buffer) => chunks.push(c));
    process.stdin.on("end", () => {
      process.stdout.write(preprocessMarkdown(Buffer.concat(chunks).toString("utf-8")));
    });
    return;
  }

  const inputPath = args[0];
  const outputPath = args[1] ?? null;
  const text = readFileSync(inputPath, "utf-8");
  const result = preprocessMarkdown(text);

  if (outputPath) {
    writeFileSync(outputPath, result, "utf-8");
  } else {
    process.stdout.write(result);
  }
}

if (process.argv[1]?.endsWith("preprocess.ts")) {
  main();
}