import fs from "node:fs/promises";
import path from "node:path";
import { fileURLToPath } from "node:url";

const scriptDir = path.dirname(fileURLToPath(import.meta.url));
const repoRoot = path.resolve(scriptDir, "..");
const registryIndexPath = path.join(repoRoot, "registry", "index.json");

function toPosixPath(value) {
  return value.split(path.sep).join(path.posix.sep);
}

async function readJson(filePath) {
  const source = await fs.readFile(filePath, "utf8");
  return JSON.parse(source);
}

function sortObject(input) {
  return Object.fromEntries(Object.entries(input).sort(([left], [right]) => left.localeCompare(right)));
}

function parseArgs(argv) {
  const options = {
    dryRun: false,
    project: process.cwd(),
    skipPackageJson: false,
    targetDir: null
  };
  const items = [];

  for (let index = 0; index < argv.length; index += 1) {
    const current = argv[index];

    if (current === "--dry-run") {
      options.dryRun = true;
      continue;
    }

    if (current === "--skip-package-json") {
      options.skipPackageJson = true;
      continue;
    }

    if (current === "--project" || current === "--target-dir") {
      const next = argv[index + 1];

      if (!next) {
        throw new Error(`Expected a value after ${current}.`);
      }

      if (current === "--project") {
        options.project = next;
      } else {
        options.targetDir = next;
      }

      index += 1;
      continue;
    }

    if (current.startsWith("--")) {
      throw new Error(`Unknown option: ${current}`);
    }

    items.push(current);
  }

  return {
    items,
    options
  };
}

function mapSourceToTarget(sourcePath, targetDir) {
  if (sourcePath.startsWith("packages/ui/src/")) {
    return toPosixPath(path.posix.join(targetDir, sourcePath.replace("packages/ui/src/", "")));
  }

  if (sourcePath.startsWith("packages/tokens/src/")) {
    return toPosixPath(
      path.posix.join(targetDir, "tokens", sourcePath.replace("packages/tokens/src/", ""))
    );
  }

  throw new Error(`Unsupported registry source path: ${sourcePath}`);
}

function resolveItems(registryIndex, requestedItems) {
  const itemLookup = new Map(registryIndex.items.map((item) => [item.name, item]));
  const resolved = new Map();
  const stack = [...requestedItems];

  while (stack.length > 0) {
    const name = stack.pop();
    const item = itemLookup.get(name);

    if (!item) {
      const available = [...itemLookup.keys()].sort().join(", ");
      throw new Error(`Unknown registry item "${name}". Available items: ${available}.`);
    }

    if (resolved.has(name)) {
      continue;
    }

    resolved.set(name, item);

    for (const dependency of item.requires) {
      stack.push(dependency);
    }
  }

  return [...resolved.values()].sort((left, right) => left.name.localeCompare(right.name));
}

async function readInstallManifest(manifestPath) {
  try {
    return await readJson(manifestPath);
  } catch {
    return null;
  }
}

function collectPackageDependencies(items) {
  const dependencies = {};

  for (const item of items) {
    for (const [name, range] of Object.entries(item.packageDependencies)) {
      dependencies[name] = range;
    }
  }

  return sortObject(dependencies);
}

function upsertDependencySections(packageJson, dependencies) {
  const sections = ["dependencies", "devDependencies", "peerDependencies", "optionalDependencies"];
  const added = {};
  const conflicts = [];
  const nextPackageJson = JSON.parse(JSON.stringify(packageJson));
  nextPackageJson.dependencies = nextPackageJson.dependencies ?? {};

  for (const [name, range] of Object.entries(dependencies)) {
    let existingSection = null;
    let existingRange = null;

    for (const section of sections) {
      const value = nextPackageJson[section]?.[name];

      if (typeof value === "string") {
        existingSection = section;
        existingRange = value;
        break;
      }
    }

    if (!existingSection) {
      nextPackageJson.dependencies[name] = range;
      added[name] = range;
      continue;
    }

    if (existingRange !== range) {
      conflicts.push({
        existingRange,
        name,
        requiredRange: range,
        section: existingSection
      });
    }
  }

  nextPackageJson.dependencies = sortObject(nextPackageJson.dependencies);

  return {
    added,
    conflicts,
    packageJson: nextPackageJson
  };
}

async function copyRegistryFiles({ dryRun, items, projectRoot, targetDir }) {
  const writtenFiles = [];
  const updatedFiles = [];
  const unchangedFiles = [];

  for (const item of items) {
    for (const sourcePath of item.files) {
      const sourceFile = path.join(repoRoot, ...sourcePath.split("/"));
      const targetRelativePath = mapSourceToTarget(sourcePath, targetDir);
      const targetFile = path.join(projectRoot, ...targetRelativePath.split("/"));
      const content = await fs.readFile(sourceFile, "utf8");
      let existingContent = null;

      try {
        existingContent = await fs.readFile(targetFile, "utf8");
      } catch {
        existingContent = null;
      }

      if (existingContent === content) {
        unchangedFiles.push(targetRelativePath);
        continue;
      }

      if (!dryRun) {
        await fs.mkdir(path.dirname(targetFile), { recursive: true });
        await fs.writeFile(targetFile, content);
      }

      if (existingContent === null) {
        writtenFiles.push(targetRelativePath);
      } else {
        updatedFiles.push(targetRelativePath);
      }
    }
  }

  return {
    unchangedFiles,
    updatedFiles,
    writtenFiles
  };
}

async function main() {
  const { items: requestedItems, options } = parseArgs(process.argv.slice(2));
  const registryIndex = await readJson(registryIndexPath);
  const projectRoot = path.resolve(options.project);
  const targetDir = toPosixPath(options.targetDir ?? registryIndex.install.defaultTargetDir);
  const targetRoot = path.join(projectRoot, ...targetDir.split("/"));
  const manifestPath = path.join(targetRoot, registryIndex.install.manifestFile);

  let itemNames = requestedItems;

  if (itemNames.length === 0) {
    const manifest = await readInstallManifest(manifestPath);

    if (!manifest?.items?.length) {
      throw new Error(
        `No registry items were provided and ${toPosixPath(
          path.relative(projectRoot, manifestPath)
        )} does not exist yet.`
      );
    }

    itemNames = manifest.items;
  }

  const resolvedItems = resolveItems(registryIndex, itemNames);
  const packageDependencies = collectPackageDependencies(resolvedItems);
  const copyResult = await copyRegistryFiles({
    dryRun: options.dryRun,
    items: resolvedItems,
    projectRoot,
    targetDir
  });

  let dependencyResult = {
    added: {},
    conflicts: []
  };

  if (!options.skipPackageJson) {
    const packageJsonPath = path.join(projectRoot, "package.json");
    const packageJson = await readJson(packageJsonPath);
    dependencyResult = upsertDependencySections(packageJson, packageDependencies);

    if (!options.dryRun) {
      await fs.writeFile(
        packageJsonPath,
        `${JSON.stringify(dependencyResult.packageJson, null, 2)}\n`
      );
    }
  }

  const installManifest = {
    items: resolvedItems.map((item) => item.name),
    packageDependencies,
    registry: registryIndex.library.name,
    sourcePackages: registryIndex.library.packages,
    targetDir
  };

  if (!options.dryRun) {
    await fs.mkdir(targetRoot, { recursive: true });
    await fs.writeFile(manifestPath, `${JSON.stringify(installManifest, null, 2)}\n`);
  }

  console.log(
    `${options.dryRun ? "Planned" : "Installed"} registry items: ${resolvedItems
      .map((item) => item.name)
      .join(", ")}`
  );
  console.log(
    `Files written: ${copyResult.writtenFiles.length}, updated: ${copyResult.updatedFiles.length}, unchanged: ${copyResult.unchangedFiles.length}`
  );

  if (!options.skipPackageJson) {
    const added = Object.keys(dependencyResult.added);
    console.log(
      added.length > 0
        ? `Added package dependencies: ${added.join(", ")}`
        : "Added package dependencies: none"
    );
  }

  if (dependencyResult.conflicts.length > 0) {
    console.log("Dependency version conflicts:");

    for (const conflict of dependencyResult.conflicts) {
      console.log(
        `- ${conflict.name}: keeping ${conflict.section}=${conflict.existingRange}, registry expects ${conflict.requiredRange}`
      );
    }
  }

  console.log(`Target directory: ${targetDir}`);
  console.log(`Tokens import path: ${targetDir}/tokens/styles.css`);
  console.log(
    options.dryRun
      ? "Dry run complete."
      : "Review the diff, then run your package manager install if package.json changed."
  );
}

await main();