const fs = require('fs');
const os = require('os');
const path = require('path');

function normalizeRelativePath(relativePath) {
  return String(relativePath || '')
    .replace(/\\/g, '/')
    .replace(/^\.\/+/, '')
    .replace(/\/+$/, '');
}

function resolveBaseRoot(scope, input = {}) {
  if (scope === 'home') {
    return input.homeDir || os.homedir();
  }

  if (scope === 'project') {
    const projectRoot = input.projectRoot || input.repoRoot;
    if (!projectRoot) {
      throw new Error('projectRoot or repoRoot is required for project install targets');
    }
    return projectRoot;
  }

  throw new Error(`Unsupported install target scope: ${scope}`);
}

function buildValidationIssue(severity, code, message, extra = {}) {
  return {
    severity,
    code,
    message,
    ...extra,
  };
}

function listRelativeFiles(dirPath, prefix = '') {
  if (!fs.existsSync(dirPath)) {
    return [];
  }

  const entries = fs.readdirSync(dirPath, { withFileTypes: true }).sort((left, right) => (
    left.name.localeCompare(right.name)
  ));
  const files = [];

  for (const entry of entries) {
    const entryPrefix = prefix ? path.join(prefix, entry.name) : entry.name;
    const absolutePath = path.join(dirPath, entry.name);

    if (entry.isDirectory()) {
      files.push(...listRelativeFiles(absolutePath, entryPrefix));
    } else if (entry.isFile()) {
      files.push(normalizeRelativePath(entryPrefix));
    }
  }

  return files;
}

function createManagedOperation({
  kind = 'copy-path',
  moduleId,
  sourceRelativePath,
  destinationPath,
  strategy = 'preserve-relative-path',
  ownership = 'managed',
  scaffoldOnly = true,
  ...rest
}) {
  return {
    kind,
    moduleId,
    sourceRelativePath: normalizeRelativePath(sourceRelativePath),
    destinationPath,
    strategy,
    ownership,
    scaffoldOnly,
    ...rest,
  };
}

function defaultValidateAdapterInput(config, input = {}) {
  if (config.kind === 'project' && !input.projectRoot && !input.repoRoot) {
    return [
      buildValidationIssue(
        'error',
        'missing-project-root',
        'projectRoot or repoRoot is required for project install targets'
      ),
    ];
  }

  if (config.kind === 'home' && !input.homeDir && !os.homedir()) {
    return [
      buildValidationIssue(
        'error',
        'missing-home-dir',
        'homeDir is required for home install targets'
      ),
    ];
  }

  return [];
}

function createRemappedOperation(adapter, moduleId, sourceRelativePath, destinationPath, options = {}) {
  return createManagedOperation({
    kind: options.kind || 'copy-path',
    moduleId,
    sourceRelativePath,
    destinationPath,
    strategy: options.strategy || 'preserve-relative-path',
    ownership: options.ownership || 'managed',
    scaffoldOnly: Object.hasOwn(options, 'scaffoldOnly') ? options.scaffoldOnly : true,
    ...options.extra,
  });
}

function createNamespacedFlatRuleOperations(adapter, moduleId, sourceRelativePath, input = {}) {
  const normalizedSourcePath = normalizeRelativePath(sourceRelativePath);
  const sourceRoot = path.join(input.repoRoot || '', normalizedSourcePath);

  if (!input.repoRoot || !fs.existsSync(sourceRoot) || !fs.statSync(sourceRoot).isDirectory()) {
    return [];
  }

  const targetRulesDir = path.join(adapter.resolveRoot(input), 'rules');
  const operations = [];
  const entries = fs.readdirSync(sourceRoot, { withFileTypes: true }).sort((left, right) => (
    left.name.localeCompare(right.name)
  ));

  for (const entry of entries) {
    const namespace = entry.name;
    const entryPath = path.join(sourceRoot, entry.name);

    if (entry.isDirectory()) {
      const relativeFiles = listRelativeFiles(entryPath);
      for (const relativeFile of relativeFiles) {
        const flattenedFileName = `${namespace}-${normalizeRelativePath(relativeFile).replace(/\//g, '-')}`;
        const sourceRelativeFile = path.join(normalizedSourcePath, namespace, relativeFile);
        operations.push(createManagedOperation({
          moduleId,
          sourceRelativePath: sourceRelativeFile,
          destinationPath: path.join(targetRulesDir, flattenedFileName),
          strategy: 'flatten-copy',
        }));
      }
    } else if (entry.isFile()) {
      operations.push(createManagedOperation({
        moduleId,
        sourceRelativePath: path.join(normalizedSourcePath, entry.name),
        destinationPath: path.join(targetRulesDir, entry.name),
        strategy: 'flatten-copy',
      }));
    }
  }

  return operations;
}

function createFlatRuleOperations({ moduleId, repoRoot, sourceRelativePath, destinationDir }) {
  const normalizedSourcePath = normalizeRelativePath(sourceRelativePath);
  const sourceRoot = path.join(repoRoot || '', normalizedSourcePath);

  if (!repoRoot || !fs.existsSync(sourceRoot) || !fs.statSync(sourceRoot).isDirectory()) {
    return [];
  }

  const operations = [];
  const entries = fs.readdirSync(sourceRoot, { withFileTypes: true }).sort((left, right) => (
    left.name.localeCompare(right.name)
  ));

  for (const entry of entries) {
    const namespace = entry.name;
    const entryPath = path.join(sourceRoot, entry.name);

    if (entry.isDirectory()) {
      const relativeFiles = listRelativeFiles(entryPath);
      for (const relativeFile of relativeFiles) {
        const flattenedFileName = `${namespace}-${normalizeRelativePath(relativeFile).replace(/\//g, '-')}`;
        operations.push(createManagedOperation({
          moduleId,
          sourceRelativePath: path.join(normalizedSourcePath, namespace, relativeFile),
          destinationPath: path.join(destinationDir, flattenedFileName),
          strategy: 'flatten-copy',
        }));
      }
    } else if (entry.isFile()) {
      operations.push(createManagedOperation({
        moduleId,
        sourceRelativePath: path.join(normalizedSourcePath, entry.name),
        destinationPath: path.join(destinationDir, entry.name),
        strategy: 'flatten-copy',
      }));
    }
  }

  return operations;
}

function createInstallTargetAdapter(config) {
  const adapter = {
    id: config.id,
    target: config.target,
    kind: config.kind,
    nativeRootRelativePath: config.nativeRootRelativePath || null,
    supports(target) {
      return target === config.target || target === config.id;
    },
    resolveRoot(input = {}) {
      const baseRoot = resolveBaseRoot(config.kind, input);
      return path.join(baseRoot, ...config.rootSegments);
    },
    getInstallStatePath(input = {}) {
      const root = adapter.resolveRoot(input);
      return path.join(root, ...config.installStatePathSegments);
    },
    resolveDestinationPath(sourceRelativePath, input = {}) {
      const normalizedSourcePath = normalizeRelativePath(sourceRelativePath);
      const targetRoot = adapter.resolveRoot(input);

      if (
        config.nativeRootRelativePath
        && normalizedSourcePath === normalizeRelativePath(config.nativeRootRelativePath)
      ) {
        return targetRoot;
      }

      return path.join(targetRoot, normalizedSourcePath);
    },
    determineStrategy(sourceRelativePath) {
      const normalizedSourcePath = normalizeRelativePath(sourceRelativePath);

      if (
        config.nativeRootRelativePath
        && normalizedSourcePath === normalizeRelativePath(config.nativeRootRelativePath)
      ) {
        return 'sync-root-children';
      }

      return 'preserve-relative-path';
    },
    createScaffoldOperation(moduleId, sourceRelativePath, input = {}) {
      const normalizedSourcePath = normalizeRelativePath(sourceRelativePath);
      return createManagedOperation({
        moduleId,
        sourceRelativePath: normalizedSourcePath,
        destinationPath: adapter.resolveDestinationPath(normalizedSourcePath, input),
        strategy: adapter.determineStrategy(normalizedSourcePath),
      });
    },
    planOperations(input = {}) {
      if (typeof config.planOperations === 'function') {
        return config.planOperations(input, adapter);
      }

      if (Array.isArray(input.modules)) {
        return input.modules.flatMap(module => {
          const paths = Array.isArray(module.paths) ? module.paths : [];
          return paths.map(sourceRelativePath => adapter.createScaffoldOperation(
            module.id,
            sourceRelativePath,
            input
          ));
        });
      }

      const module = input.module || {};
      const paths = Array.isArray(module.paths) ? module.paths : [];
      return paths.map(sourceRelativePath => adapter.createScaffoldOperation(
        module.id,
        sourceRelativePath,
        input
      ));
    },
    validate(input = {}) {
      if (typeof config.validate === 'function') {
        return config.validate(input, adapter);
      }

      return defaultValidateAdapterInput(config, input);
    },
  };

  return Object.freeze(adapter);
}

module.exports = {
  buildValidationIssue,
  createFlatRuleOperations,
  createInstallTargetAdapter,
  createManagedOperation,
  createManagedScaffoldOperation: (moduleId, sourceRelativePath, destinationPath, strategy) => (
    createManagedOperation({
      moduleId,
      sourceRelativePath,
      destinationPath,
      strategy,
    })
  ),
  createNamespacedFlatRuleOperations,
  createRemappedOperation,
  normalizeRelativePath,
};