import { readFile } from "node:fs/promises";
import { dirname, basename } from "node:path";
import type {
  CodeStructure,
  FileNode,
  ModuleNode,
  DependencyEdge,
  ExportNode,
} from "@codeboard/shared";
import { walkFiles } from "./file-walker.js";
import { typescriptParser } from "./languages/typescript.js";
import { pythonParser } from "./languages/python.js";
import type { LanguageParser } from "./languages/base.js";

const MAX_FILES = 200;

const parsers: LanguageParser[] = [typescriptParser, pythonParser];

function getParser(language: string): LanguageParser | null {
  return (
    parsers.find((p) =>
      p.extensions.some((ext) => {
        const langMap: Record<string, string[]> = {
          typescript: [".ts", ".tsx"],
          javascript: [".js", ".jsx", ".mjs", ".cjs"],
          python: [".py"],
        };
        return langMap[language]?.includes(ext);
      })
    ) ?? null
  );
}

function buildModules(files: FileNode[]): ModuleNode[] {
  const dirMap = new Map<string, string[]>();

  for (const file of files) {
    const dir = dirname(file.path);
    const existing = dirMap.get(dir);
    if (existing) {
      existing.push(file.path);
    } else {
      dirMap.set(dir, [file.path]);
    }
  }

  return Array.from(dirMap.entries()).map(([dirPath, filePaths]) => ({
    name: basename(dirPath) || "root",
    path: dirPath,
    files: filePaths,
  }));
}

function buildDependencies(files: FileNode[]): DependencyEdge[] {
  const edges: DependencyEdge[] = [];
  const filePathSet = new Set(files.map((f) => f.path));

  for (const file of files) {
    for (const imp of file.imports) {
      let resolved = imp.source;

      if (resolved.startsWith(".")) {
        const dir = dirname(file.path);
        const candidate = `${dir}/${resolved.replace(/^\.\//, "")}`;
        const extensions = [".ts", ".tsx", ".js", ".jsx", ".py", ""];
        for (const ext of extensions) {
          if (filePathSet.has(candidate + ext)) {
            resolved = candidate + ext;
            break;
          }
          if (filePathSet.has(`${candidate}/index${ext}`)) {
            resolved = `${candidate}/index${ext}`;
            break;
          }
        }
      }

      edges.push({
        source: file.path,
        target: resolved,
        type: "import",
      });
    }
  }

  return edges;
}

function detectEntryPoints(files: FileNode[]): string[] {
  const entryNames = new Set([
    "index",
    "main",
    "app",
    "server",
    "mod",
    "lib",
    "__init__",
  ]);

  return files
    .filter((f) => {
      const name = basename(f.path).replace(/\.[^.]+$/, "");
      return entryNames.has(name);
    })
    .map((f) => f.path);
}

function collectExports(files: FileNode[]): ExportNode[] {
  const allExports: ExportNode[] = [];
  for (const file of files) {
    allExports.push(...file.exports);
  }
  return allExports;
}

export async function analyzeRepository(
  repoPath: string
): Promise<CodeStructure> {
  const walkedFiles = await walkFiles(repoPath);
  const filesToAnalyze = walkedFiles.slice(0, MAX_FILES);

  const parsedFiles: FileNode[] = [];

  for (const walkedFile of filesToAnalyze) {
    const parser = getParser(walkedFile.language);
    if (!parser) continue;

    try {
      const content = await readFile(walkedFile.absolutePath, "utf-8");
      const fileNode = parser.parse(content, walkedFile.relativePath);
      parsedFiles.push(fileNode);
    } catch {
      continue;
    }
  }

  const modules = buildModules(parsedFiles);
  const dependencies = buildDependencies(parsedFiles);
  const entryPoints = detectEntryPoints(parsedFiles);
  const exports = collectExports(parsedFiles);

  return {
    files: parsedFiles,
    modules,
    entryPoints,
    exports,
    dependencies,
    patterns: [],
  };
}