import * as plugins from '../plugins.js';
import type {
  IFileMetadata,
  IFileDependencies,
  IFileAnalysis,
  IAnalysisResult,
  TaskType,
  IPrioritizationWeights,
  ITierConfig,
} from './types.js';

/**
 * ContextAnalyzer provides intelligent file selection and prioritization
 * based on dependency analysis, task relevance, and configurable weights
 */
export class ContextAnalyzer {
  private projectRoot: string;
  private weights: Required<IPrioritizationWeights>;
  private tiers: Required<ITierConfig>;

  /**
   * Creates a new ContextAnalyzer
   * @param projectRoot - Root directory of the project
   * @param weights - Prioritization weights
   * @param tiers - Tier configuration
   */
  constructor(
    projectRoot: string,
    weights: Partial<IPrioritizationWeights> = {},
    tiers: Partial<ITierConfig> = {}
  ) {
    this.projectRoot = projectRoot;

    // Default weights
    this.weights = {
      dependencyWeight: weights.dependencyWeight ?? 0.3,
      relevanceWeight: weights.relevanceWeight ?? 0.4,
      efficiencyWeight: weights.efficiencyWeight ?? 0.2,
      recencyWeight: weights.recencyWeight ?? 0.1,
    };

    // Default tiers
    this.tiers = {
      essential: tiers.essential ?? { minScore: 0.8, trimLevel: 'none' },
      important: tiers.important ?? { minScore: 0.5, trimLevel: 'light' },
      optional: tiers.optional ?? { minScore: 0.2, trimLevel: 'aggressive' },
    };
  }

  /**
   * Analyzes files for a specific task type
   * @param metadata - Array of file metadata to analyze
   * @param taskType - Type of task being performed
   * @param changedFiles - Optional list of recently changed files (for commits)
   * @returns Analysis result with scored files
   */
  public async analyze(
    metadata: IFileMetadata[],
    taskType: TaskType,
    changedFiles: string[] = []
  ): Promise<IAnalysisResult> {
    const startTime = Date.now();

    // Build dependency graph
    const dependencyGraph = await this.buildDependencyGraph(metadata);

    // Calculate centrality scores
    this.calculateCentrality(dependencyGraph);

    // Analyze each file
    const files: IFileAnalysis[] = [];
    for (const meta of metadata) {
      const analysis = await this.analyzeFile(
        meta,
        taskType,
        dependencyGraph,
        changedFiles
      );
      files.push(analysis);
    }

    // Sort by importance score (highest first)
    files.sort((a, b) => b.importanceScore - a.importanceScore);

    const analysisDuration = Date.now() - startTime;

    return {
      taskType,
      files,
      dependencyGraph,
      totalFiles: metadata.length,
      analysisDuration,
    };
  }

  /**
   * Builds a dependency graph from file metadata
   * @param metadata - Array of file metadata
   * @returns Dependency graph as a map
   */
  private async buildDependencyGraph(
    metadata: IFileMetadata[]
  ): Promise<Map<string, IFileDependencies>> {
    const graph = new Map<string, IFileDependencies>();

    // Initialize graph entries
    for (const meta of metadata) {
      graph.set(meta.path, {
        path: meta.path,
        imports: [],
        importedBy: [],
        centrality: 0,
      });
    }

    // Parse imports from each file
    for (const meta of metadata) {
      try {
        const contents = await plugins.smartfile.fs.toStringSync(meta.path);
        const imports = this.extractImports(contents, meta.path);

        const deps = graph.get(meta.path)!;
        deps.imports = imports;

        // Update importedBy for imported files
        for (const importPath of imports) {
          const importedDeps = graph.get(importPath);
          if (importedDeps) {
            importedDeps.importedBy.push(meta.path);
          }
        }
      } catch (error) {
        console.warn(`Failed to parse imports from ${meta.path}:`, error.message);
      }
    }

    return graph;
  }

  /**
   * Extracts import statements from file contents
   * @param contents - File contents
   * @param filePath - Path of the file being analyzed
   * @returns Array of absolute paths to imported files
   */
  private extractImports(contents: string, filePath: string): string[] {
    const imports: string[] = [];
    const fileDir = plugins.path.dirname(filePath);

    // Match various import patterns
    const importRegex = /(?:import|export).*?from\s+['"](.+?)['"]/g;
    let match;

    while ((match = importRegex.exec(contents)) !== null) {
      const importPath = match[1];

      // Skip external modules
      if (!importPath.startsWith('.')) {
        continue;
      }

      // Resolve relative import to absolute path
      let resolvedPath = plugins.path.resolve(fileDir, importPath);

      // Handle various file extensions
      const extensions = ['.ts', '.js', '.tsx', '.jsx', '/index.ts', '/index.js'];
      let found = false;

      for (const ext of extensions) {
        const testPath = resolvedPath.endsWith(ext) ? resolvedPath : resolvedPath + ext;
        try {
          // Use synchronous file check to avoid async in this context
          const fs = require('fs');
          const exists = fs.existsSync(testPath);
          if (exists) {
            imports.push(testPath);
            found = true;
            break;
          }
        } catch (error) {
          // Continue trying other extensions
        }
      }

      if (!found && !resolvedPath.includes('.')) {
        // Try with .ts extension as default
        imports.push(resolvedPath + '.ts');
      }
    }

    return imports;
  }

  /**
   * Calculates centrality scores for all nodes in the dependency graph
   * Uses a simplified PageRank-like algorithm
   * @param graph - Dependency graph
   */
  private calculateCentrality(graph: Map<string, IFileDependencies>): void {
    const damping = 0.85;
    const iterations = 10;
    const nodeCount = graph.size;

    // Initialize scores
    const scores = new Map<string, number>();
    for (const path of graph.keys()) {
      scores.set(path, 1.0 / nodeCount);
    }

    // Iterative calculation
    for (let i = 0; i < iterations; i++) {
      const newScores = new Map<string, number>();

      for (const [path, deps] of graph.entries()) {
        let score = (1 - damping) / nodeCount;

        // Add contributions from nodes that import this file
        for (const importerPath of deps.importedBy) {
          const importerDeps = graph.get(importerPath);
          if (importerDeps) {
            const importerScore = scores.get(importerPath) ?? 0;
            const outgoingCount = importerDeps.imports.length || 1;
            score += damping * (importerScore / outgoingCount);
          }
        }

        newScores.set(path, score);
      }

      // Update scores
      for (const [path, score] of newScores) {
        scores.set(path, score);
      }
    }

    // Normalize scores to 0-1 range
    const maxScore = Math.max(...scores.values());
    if (maxScore > 0) {
      for (const deps of graph.values()) {
        const score = scores.get(deps.path) ?? 0;
        deps.centrality = score / maxScore;
      }
    }
  }

  /**
   * Analyzes a single file
   * @param meta - File metadata
   * @param taskType - Task being performed
   * @param graph - Dependency graph
   * @param changedFiles - Recently changed files
   * @returns File analysis
   */
  private async analyzeFile(
    meta: IFileMetadata,
    taskType: TaskType,
    graph: Map<string, IFileDependencies>,
    changedFiles: string[]
  ): Promise<IFileAnalysis> {
    const deps = graph.get(meta.path);
    const centralityScore = deps?.centrality ?? 0;

    // Calculate task-specific relevance
    const relevanceScore = this.calculateRelevance(meta, taskType);

    // Calculate efficiency (information per token)
    const efficiencyScore = this.calculateEfficiency(meta);

    // Calculate recency (for commit tasks)
    const recencyScore = this.calculateRecency(meta, changedFiles);

    // Calculate combined importance score
    const importanceScore =
      relevanceScore * this.weights.relevanceWeight +
      centralityScore * this.weights.dependencyWeight +
      efficiencyScore * this.weights.efficiencyWeight +
      recencyScore * this.weights.recencyWeight;

    // Assign tier
    const tier = this.assignTier(importanceScore);

    return {
      path: meta.path,
      relevanceScore,
      centralityScore,
      efficiencyScore,
      recencyScore,
      importanceScore,
      tier,
      reason: this.generateReason(meta, taskType, importanceScore, tier),
    };
  }

  /**
   * Calculates task-specific relevance score
   */
  private calculateRelevance(meta: IFileMetadata, taskType: TaskType): number {
    const relativePath = meta.relativePath.toLowerCase();
    let score = 0.5; // Base score

    // README generation - prioritize public APIs and main exports
    if (taskType === 'readme') {
      if (relativePath.includes('index.ts')) score += 0.3;
      if (relativePath.match(/^ts\/[^\/]+\.ts$/)) score += 0.2; // Root level exports
      if (relativePath.includes('test/')) score -= 0.3;
      if (relativePath.includes('classes/')) score += 0.1;
      if (relativePath.includes('interfaces/')) score += 0.1;
    }

    // Commit messages - prioritize changed files and their dependencies
    if (taskType === 'commit') {
      if (relativePath.includes('test/')) score -= 0.2;
      // Recency will handle changed files
    }

    // Description generation - prioritize main exports and core interfaces
    if (taskType === 'description') {
      if (relativePath.includes('index.ts')) score += 0.4;
      if (relativePath.match(/^ts\/[^\/]+\.ts$/)) score += 0.3;
      if (relativePath.includes('test/')) score -= 0.4;
      if (relativePath.includes('interfaces/')) score += 0.2;
    }

    return Math.max(0, Math.min(1, score));
  }

  /**
   * Calculates efficiency score (information density)
   */
  private calculateEfficiency(meta: IFileMetadata): number {
    // Prefer files that are not too large (good signal-to-noise ratio)
    const optimalSize = 5000; // ~1250 tokens
    const distance = Math.abs(meta.estimatedTokens - optimalSize);
    const normalized = Math.max(0, 1 - distance / optimalSize);

    return normalized;
  }

  /**
   * Calculates recency score for changed files
   */
  private calculateRecency(meta: IFileMetadata, changedFiles: string[]): number {
    if (changedFiles.length === 0) {
      return 0;
    }

    // Check if this file was changed
    const isChanged = changedFiles.some((changed) => changed === meta.path);

    return isChanged ? 1.0 : 0.0;
  }

  /**
   * Assigns a tier based on importance score
   */
  private assignTier(score: number): 'essential' | 'important' | 'optional' | 'excluded' {
    if (score >= this.tiers.essential.minScore) return 'essential';
    if (score >= this.tiers.important.minScore) return 'important';
    if (score >= this.tiers.optional.minScore) return 'optional';
    return 'excluded';
  }

  /**
   * Generates a human-readable reason for the score
   */
  private generateReason(
    meta: IFileMetadata,
    taskType: TaskType,
    score: number,
    tier: string
  ): string {
    const reasons: string[] = [];

    if (meta.relativePath.includes('index.ts')) {
      reasons.push('main export file');
    }

    if (meta.relativePath.includes('test/')) {
      reasons.push('test file (lower priority)');
    }

    if (taskType === 'readme' && meta.relativePath.match(/^ts\/[^\/]+\.ts$/)) {
      reasons.push('root-level module');
    }

    reasons.push(`score: ${score.toFixed(2)}`);
    reasons.push(`tier: ${tier}`);

    return reasons.join(', ');
  }
}