#!/usr/bin/env node
// find-duplicate-functions.mjs
// Usage:
//   node find-duplicate-functions.mjs [rootDir] [--mode exact|struct] [--min-lines N] [--json]
// Example:
//   node find-duplicate-functions.mjs . --mode struct --min-lines 3

import fs from "fs";
import path from "path";
import * as url from "url";
import ts from "typescript";

const __dirname = path.dirname(url.fileURLToPath(import.meta.url));

/** -------- CLI OPTIONS -------- */
const args = process.argv.slice(2);
let rootDir = ".";
let mode = "struct"; // "exact" | "struct"
let minLines = 3;
let outputJson = false;

for (let i = 0; i < args.length; i++) {
  const a = args[i];
  if (!a.startsWith("--") && rootDir === ".") {
    rootDir = a;
  } else if (a === "--mode") {
    mode = (args[++i] || "struct").toLowerCase();
    if (!["exact", "struct"].includes(mode)) {
      console.error("Invalid --mode. Use 'exact' or 'struct'.");
      process.exit(1);
    }
  } else if (a === "--min-lines") {
    minLines = parseInt(args[++i] || "3", 10);
  } else if (a === "--json") {
    outputJson = true;
  }
}

/** -------- FILE DISCOVERY -------- */
const DEFAULT_IGNORES = new Set([
  "node_modules",
  ".git",
  ".next",
  ".vercel",
  "dist",
  "build",
  ".astro", // Astro's generated cache dir
]);

const VALID_EXTS = new Set([".ts", ".tsx", ".astro", ".mts", ".cts"]);

function walk(dir) {
  /** @type {string[]} */
  const out = [];
  const entries = fs.readdirSync(dir, { withFileTypes: true });
  for (const e of entries) {
    const p = path.join(dir, e.name);
    if (e.isDirectory()) {
      if (DEFAULT_IGNORES.has(e.name)) continue;
      out.push(...walk(p));
    } else if (e.isFile() && VALID_EXTS.has(path.extname(e.name))) {
      out.push(p);
    }
  }
  return out;
}

/** -------- ASTRO CODE EXTRACTION --------
 * Extract TS/JS code from:
 * - frontmatter: --- ... ---
 * - <script ...> ... </script>
 */
function extractCodeFromAstro(source) {
  /** @type {{code:string, offset:number}[]} */
  const blocks = [];

  // Frontmatter (must be at top in Astro)
  // Match the FIRST pair of --- ... ---
  const fm = source.startsWith("---")
    ? (() => {
        const end = source.indexOf("\n---", 3);
        if (end !== -1) {
          const front = source.slice(3, end + 1); // include trailing \n
          return { start: 0, end: end + 4, code: front };
        }
        return null;
      })()
    : null;
  if (fm) {
    // offset for line numbers is after the first '---\n'
    blocks.push({ code: fm.code, offset: 4 }); // rough; we’ll fix line numbers via positions later
  }

  // <script ...> ... </script>
  const scriptRe = /<script\b[^>]*>([\s\S]*?)<\/script>/gi;
  let m;
  while ((m = scriptRe.exec(source))) {
    const code = m[1] || "";
    blocks.push({ code, offset: indexToLine(source, m.index) });
  }

  return blocks;
}

/** -------- UTIL: index -> 1-based line -------- */
function indexToLine(text, idx) {
  let line = 1;
  for (let i = 0; i < idx && i < text.length; i++) {
    if (text.charCodeAt(i) === 10) line++;
  }
  return line;
}

/** -------- AST HELPERS -------- */
function createSourceFile(virtualPath, code) {
  return ts.createSourceFile(
    virtualPath,
    code,
    ts.ScriptTarget.Latest,
    /*setParentNodes*/ true,
    virtualPath.endsWith(".tsx") ? ts.ScriptKind.TSX : ts.ScriptKind.TS
  );
}

// Normalize AST to a structural signature string
function structuralSignature(node) {
  /** @type {string[]} */
  const parts = [];
  const visit = (n) => {
    // Skip trivia: comments/whitespace are already not in AST
    const kindName = ts.SyntaxKind[n.kind] || `K${n.kind}`;
    switch (n.kind) {
      case ts.SyntaxKind.Identifier:
        parts.push("Id");
        return;
      case ts.SyntaxKind.PrivateIdentifier:
        parts.push("PrivId");
        return;
      case ts.SyntaxKind.StringLiteral:
      case ts.SyntaxKind.NoSubstitutionTemplateLiteral:
      case ts.SyntaxKind.TemplateHead:
      case ts.SyntaxKind.TemplateMiddle:
      case ts.SyntaxKind.TemplateTail:
        parts.push("Str");
        return;
      case ts.SyntaxKind.NumericLiteral:
        parts.push("Num");
        return;
      case ts.SyntaxKind.TrueKeyword:
      case ts.SyntaxKind.FalseKeyword:
        parts.push("Bool");
        return;
      case ts.SyntaxKind.NullKeyword:
      case ts.SyntaxKind.UndefinedKeyword:
        parts.push("Nil");
        return;
      case ts.SyntaxKind.PropertyAssignment:
      case ts.SyntaxKind.ShorthandPropertyAssignment:
      case ts.SyntaxKind.MethodDeclaration:
      case ts.SyntaxKind.MethodSignature:
        parts.push("Prop");
        break;
      default:
        parts.push(kindName);
    }
    n.forEachChild(visit);
  };
  visit(node);
  return parts.join("|");
}

function getFunctionInfo(sf, filePath) {
  /** @type {Array<{
    name: string,
    bodyText: string,
    structKey: string,
    start: number,
    end: number,
    startLine: number,
    endLine: number
  }>} */
  const out = [];

  const addFunc = (nameNode, bodyNode) => {
    if (!bodyNode) return;
    const bodyText = bodyNode.getText(sf).trim();
    const start = bodyNode.getStart(sf);
    const end = bodyNode.getEnd();
    const { line: startLine } = sf.getLineAndCharacterOfPosition(start);
    const { line: endLine } = sf.getLineAndCharacterOfPosition(end);
    const name =
      nameNode && ts.isIdentifier(nameNode) ? nameNode.escapedText.toString() : "(anonymous)";

    // min-lines filter
    const lines = bodyText.split(/\r?\n/).filter(Boolean);
    if (lines.length < minLines) return;

    // structural signature from the body
    const structKey = structuralSignature(bodyNode);

    out.push({
      name,
      bodyText,
      structKey,
      start,
      end,
      startLine: startLine + 1,
      endLine: endLine + 1,
    });
  };

  const visit = (node) => {
    if (ts.isFunctionDeclaration(node) && node.body) {
      addFunc(node.name ?? null, node.body);
    } else if (
      ts.isFunctionExpression(node) ||
      ts.isArrowFunction(node)
    ) {
      // find name if it’s assigned: const foo = () => {}
      let name = null;
      if (node.parent && ts.isVariableDeclaration(node.parent) && node.parent.name) {
        name = node.parent.name;
      } else if (
        node.parent &&
        ts.isPropertyAssignment(node.parent) &&
        ts.isIdentifier(node.parent.name)
      ) {
        name = node.parent.name;
      } else if (node.name) {
        name = node.name;
      }
      if (node.body) addFunc(name, node.body);
    } else if (ts.isMethodDeclaration(node) && node.body) {
      addFunc(node.name, node.body);
    }
    node.forEachChild(visit);
  };

  visit(sf);
  return out;
}

/** -------- MAIN SCAN -------- */
const files = walk(path.resolve(process.cwd(), rootDir));

/** Maps from hash -> occurrences */
const groups = new Map();
/** Helper for exact hash */
import crypto from "crypto";
const exactHash = (text) => crypto.createHash("sha1").update(text.replace(/\s+/g, " ").trim()).digest("hex");

for (const file of files) {
  try {
    const ext = path.extname(file).toLowerCase();
    const raw = fs.readFileSync(file, "utf8");

    /** @type {Array<{virtualPath:string, code:string, lineOffset:number}>} */
    const codeUnits = [];

    if (ext === ".astro") {
      const blocks = extractCodeFromAstro(raw);
      blocks.forEach((b, i) => {
        codeUnits.push({
          virtualPath: file + `#astro${i + 1}.ts`,
          code: b.code,
          lineOffset: b.offset || 1,
        });
      });
    } else {
      codeUnits.push({ virtualPath: file, code: raw, lineOffset: 1 });
    }

    for (const { virtualPath, code, lineOffset } of codeUnits) {
      const sf = createSourceFile(virtualPath, code);
      const funcs = getFunctionInfo(sf, file);
      for (const f of funcs) {
        const key =
          mode === "exact" ? exactHash(f.bodyText) : crypto.createHash("sha1").update(f.structKey).digest("hex");
        const item = {
          file,
          where:
            ext === ".astro"
              ? `${path.relative(process.cwd(), file)}:${f.startLine + lineOffset - 1}-${f.endLine + lineOffset - 1}`
              : `${path.relative(process.cwd(), file)}:${f.startLine}-${f.endLine}`,
          name: f.name,
          lines: f.endLine - f.startLine + 1,
          preview: f.bodyText.split(/\r?\n/).slice(0, 5).join("\n") + (f.endLine - f.startLine + 1 > 5 ? "\n..." : ""),
        };
        if (!groups.has(key)) groups.set(key, []);
        groups.get(key).push(item);
      }
    }
  } catch (e) {
    console.warn(`⚠️ Skipping ${file}: ${e.message}`);
  }
}

/** -------- REPORT -------- */
const dupes = [...groups.entries()]
  .map(([key, arr]) => ({ key, items: arr }))
  .filter((g) => g.items.length > 1)
  .sort((a, b) => b.items.length - a.items.length);

if (outputJson) {
  console.log(JSON.stringify({ mode, minLines, groups: dupes }, null, 2));
  process.exit(0);
}

if (dupes.length === 0) {
  console.log(`✅ No duplicate functions found (mode=${mode}, min-lines=${minLines}).`);
  process.exit(0);
}

console.log(`\nFound ${dupes.length} duplicate group(s) (mode=${mode}, min-lines=${minLines}):\n`);
dupes.forEach((g, i) => {
  console.log(`== Group ${i + 1} (${g.items.length} matches) ==`);
  const example = g.items[0];
  console.log(`   Sample (${example.lines} lines) from ${example.where}${example.name ? ` [${example.name}]` : ""}`);
  console.log("   ---");
  console.log(indent(example.preview, "   "));
  console.log("   ---");
  g.items.forEach((it) => {
    console.log(` • ${it.where}${it.name ? ` [${it.name}]` : ""} (${it.lines} lines)`);
  });
  console.log();
});

function indent(s, pre) {
  return s
    .split("\n")
    .map((l) => pre + l)
    .join("\n");
}