import * as plugins from '../plugins.js';
import type { Document, IStoredDocument, ISortSpecification, ISortDirection } from '../types/interfaces.js';

// Import mingo Query class
import { Query } from 'mingo';

/**
 * Query engine using mingo for MongoDB-compatible query matching
 */
export class QueryEngine {
  /**
   * Filter documents by a MongoDB query filter
   */
  static filter(documents: IStoredDocument[], filter: Document): IStoredDocument[] {
    if (!filter || Object.keys(filter).length === 0) {
      return documents;
    }

    const query = new Query(filter);
    return documents.filter(doc => query.test(doc));
  }

  /**
   * Test if a single document matches a filter
   */
  static matches(document: Document, filter: Document): boolean {
    if (!filter || Object.keys(filter).length === 0) {
      return true;
    }

    const query = new Query(filter);
    return query.test(document);
  }

  /**
   * Find a single document matching the filter
   */
  static findOne(documents: IStoredDocument[], filter: Document): IStoredDocument | null {
    if (!filter || Object.keys(filter).length === 0) {
      return documents[0] || null;
    }

    const query = new Query(filter);
    for (const doc of documents) {
      if (query.test(doc)) {
        return doc;
      }
    }
    return null;
  }

  /**
   * Sort documents by a sort specification
   */
  static sort(documents: IStoredDocument[], sort: ISortSpecification): IStoredDocument[] {
    if (!sort) {
      return documents;
    }

    // Normalize sort specification to array of [field, direction] pairs
    const sortFields: Array<[string, number]> = [];

    if (Array.isArray(sort)) {
      for (const [field, direction] of sort) {
        sortFields.push([field, this.normalizeDirection(direction)]);
      }
    } else {
      for (const [field, direction] of Object.entries(sort)) {
        sortFields.push([field, this.normalizeDirection(direction)]);
      }
    }

    return [...documents].sort((a, b) => {
      for (const [field, direction] of sortFields) {
        const aVal = this.getNestedValue(a, field);
        const bVal = this.getNestedValue(b, field);

        const comparison = this.compareValues(aVal, bVal);
        if (comparison !== 0) {
          return comparison * direction;
        }
      }
      return 0;
    });
  }

  /**
   * Apply projection to documents
   */
  static project(documents: IStoredDocument[], projection: Document): Document[] {
    if (!projection || Object.keys(projection).length === 0) {
      return documents;
    }

    // Determine if this is inclusion or exclusion projection
    const keys = Object.keys(projection);
    const hasInclusion = keys.some(k => k !== '_id' && projection[k] === 1);
    const hasExclusion = keys.some(k => k !== '_id' && projection[k] === 0);

    // Can't mix inclusion and exclusion (except for _id)
    if (hasInclusion && hasExclusion) {
      throw new Error('Cannot mix inclusion and exclusion in projection');
    }

    return documents.map(doc => {
      if (hasInclusion) {
        // Inclusion projection
        const result: Document = {};

        // Handle _id
        if (projection._id !== 0 && projection._id !== false) {
          result._id = doc._id;
        }

        for (const key of keys) {
          if (key === '_id') continue;
          if (projection[key] === 1 || projection[key] === true) {
            const value = this.getNestedValue(doc, key);
            if (value !== undefined) {
              this.setNestedValue(result, key, value);
            }
          }
        }

        return result;
      } else {
        // Exclusion projection - start with copy and remove fields
        const result = { ...doc };

        for (const key of keys) {
          if (projection[key] === 0 || projection[key] === false) {
            this.deleteNestedValue(result, key);
          }
        }

        return result;
      }
    });
  }

  /**
   * Get distinct values for a field
   */
  static distinct(documents: IStoredDocument[], field: string, filter?: Document): any[] {
    let docs = documents;
    if (filter && Object.keys(filter).length > 0) {
      docs = this.filter(documents, filter);
    }

    const values = new Set<any>();
    for (const doc of docs) {
      const value = this.getNestedValue(doc, field);
      if (value !== undefined) {
        if (Array.isArray(value)) {
          // For arrays, add each element
          for (const v of value) {
            values.add(this.toComparable(v));
          }
        } else {
          values.add(this.toComparable(value));
        }
      }
    }

    return Array.from(values);
  }

  /**
   * Normalize sort direction to 1 or -1
   */
  private static normalizeDirection(direction: ISortDirection): number {
    if (typeof direction === 'number') {
      return direction > 0 ? 1 : -1;
    }
    if (direction === 'asc' || direction === 'ascending') {
      return 1;
    }
    return -1;
  }

  /**
   * Get a nested value from an object using dot notation
   */
  static getNestedValue(obj: any, path: string): any {
    const parts = path.split('.');
    let current = obj;

    for (const part of parts) {
      if (current === null || current === undefined) {
        return undefined;
      }
      if (Array.isArray(current)) {
        // Handle array access
        const index = parseInt(part, 10);
        if (!isNaN(index)) {
          current = current[index];
        } else {
          // Get the field from all array elements
          return current.map(item => this.getNestedValue(item, part)).flat();
        }
      } else {
        current = current[part];
      }
    }

    return current;
  }

  /**
   * Set a nested value in an object using dot notation
   */
  private static setNestedValue(obj: any, path: string, value: any): void {
    const parts = path.split('.');
    let current = obj;

    for (let i = 0; i < parts.length - 1; i++) {
      const part = parts[i];
      if (!(part in current)) {
        current[part] = {};
      }
      current = current[part];
    }

    current[parts[parts.length - 1]] = value;
  }

  /**
   * Delete a nested value from an object using dot notation
   */
  private static deleteNestedValue(obj: any, path: string): void {
    const parts = path.split('.');
    let current = obj;

    for (let i = 0; i < parts.length - 1; i++) {
      const part = parts[i];
      if (!(part in current)) {
        return;
      }
      current = current[part];
    }

    delete current[parts[parts.length - 1]];
  }

  /**
   * Compare two values for sorting
   */
  private static compareValues(a: any, b: any): number {
    // Handle undefined/null
    if (a === undefined && b === undefined) return 0;
    if (a === undefined) return -1;
    if (b === undefined) return 1;
    if (a === null && b === null) return 0;
    if (a === null) return -1;
    if (b === null) return 1;

    // Handle ObjectId
    if (a instanceof plugins.bson.ObjectId && b instanceof plugins.bson.ObjectId) {
      return a.toHexString().localeCompare(b.toHexString());
    }

    // Handle dates
    if (a instanceof Date && b instanceof Date) {
      return a.getTime() - b.getTime();
    }

    // Handle numbers
    if (typeof a === 'number' && typeof b === 'number') {
      return a - b;
    }

    // Handle strings
    if (typeof a === 'string' && typeof b === 'string') {
      return a.localeCompare(b);
    }

    // Handle booleans
    if (typeof a === 'boolean' && typeof b === 'boolean') {
      return (a ? 1 : 0) - (b ? 1 : 0);
    }

    // Fall back to string comparison
    return String(a).localeCompare(String(b));
  }

  /**
   * Convert a value to a comparable form (for distinct)
   */
  private static toComparable(value: any): any {
    if (value instanceof plugins.bson.ObjectId) {
      return value.toHexString();
    }
    if (value instanceof Date) {
      return value.toISOString();
    }
    if (typeof value === 'object' && value !== null) {
      return JSON.stringify(value);
    }
    return value;
  }
}