analytics-api/services/analytics_engine.ts

import * as math from 'mathjs';
import * as _ from 'lodash';
import { DataSeries, DataMatrix, Condition, ApiResponse } from '../types/index';
import { RollingWindow } from './rolling_window';
import { KMeans, KMeansOptions } from './kmeans';
import { getWeekNumber, getSameWeekDayLastYear } from './time-helper';
import { calculateLinearRegression, generateForecast, calculatePredictionIntervals, ForecastResult } from './prediction';

export const handleError = (error: unknown): string => {
  return error instanceof Error ? error.message : 'Unknown error';
};
export const validateSeries = (series: DataSeries): void => {
    if (!series || !Array.isArray(series.values) || series.values.length === 0) {
        throw new Error('Series must contain at least one value');
    }
};

export const validateMatrix = (matrix: DataMatrix): void => {
    if (!matrix || !Array.isArray(matrix.data) || matrix.data.length === 0) {
        throw new Error('Matrix must contain at least one row');
    }
};

export class AnalyticsEngine {
    
    private applyConditions(series: DataSeries, conditions: Condition[] = []): number[] {
        if (conditions.length === 0) return series.values;
        return series.values; // TODO: Implement filtering
    }

    // Basic statistical functions
    unique(series: DataSeries): number[] {
        validateSeries(series);
        return _.uniq(series.values);
    }

    mean(series: DataSeries, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        if (filteredValues.length === 0) throw new Error('No data points match conditions');
        return Number(math.mean(filteredValues));
    }

    count(series: DataSeries, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        if (filteredValues.length === 0) throw new Error('No data points match conditions');
        return filteredValues.length;
    }

    distinctCount(series: DataSeries, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        const uniqueValues = _.uniq(filteredValues);
        return uniqueValues.length;
    }

    variance(series: DataSeries, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        if (filteredValues.length === 0) throw new Error('No data points match conditions');
        return Number(math.variance(filteredValues));
    }

    standardDeviation(series: DataSeries, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        if (filteredValues.length === 0) throw new Error('No data points match conditions');
        return Number(math.std(filteredValues));
    }

    percentile(series: DataSeries, percent: number, ascending: boolean = true, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        if (filteredValues.length === 0) throw new Error('No data points match conditions');
        
        const sorted = ascending ? _.sortBy(filteredValues) : _.sortBy(filteredValues).reverse();
        const index = (percent / 100) * (sorted.length - 1);
        const lower = Math.floor(index);
        const upper = Math.ceil(index);
        const weight = index % 1;
        
        return sorted[lower] * (1 - weight) + sorted[upper] * weight;
    }

    median(series: DataSeries, conditions: Condition[] = []): number {
        return this.percentile(series, 50, true, conditions);
    }

    mode(series: DataSeries, conditions: Condition[] = []): number[] {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        const frequency = _.countBy(filteredValues);
        const maxFreq = Math.max(...Object.values(frequency));
        
        return Object.keys(frequency)
            .filter(key => frequency[key] === maxFreq)
            .map(Number);
    }

    max(series: DataSeries, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        if (filteredValues.length === 0) throw new Error('No data points match conditions');
        return Math.max(...filteredValues);
    }

    min(series: DataSeries, conditions: Condition[] = []): number {
        validateSeries(series);
        const filteredValues = this.applyConditions(series, conditions);
        if (filteredValues.length === 0) throw new Error('No data points match conditions');
        return Math.min(...filteredValues);
    }

    correlation(series1: DataSeries, series2: DataSeries): number {
        validateSeries(series1);
        validateSeries(series2);
        
        if (series1.values.length !== series2.values.length) {
            throw new Error('Series must have same length for correlation');
        }
        
        const x = series1.values;
        const y = series2.values;
        const n = x.length;
        
        const sumX = _.sum(x);
        const sumY = _.sum(y);
        const sumXY = _.sum(x.map((xi, i) => xi * y[i]));
        const sumX2 = _.sum(x.map(xi => xi * xi));
        const sumY2 = _.sum(y.map(yi => yi * yi));
        
        const numerator = n * sumXY - sumX * sumY;
        const denominator = Math.sqrt((n * sumX2 - sumX * sumX) * (n * sumY2 - sumY * sumY));
        
        return numerator / denominator;
    }

    // Rolling window functions
    rolling(series: DataSeries, windowSize: number): RollingWindow {
        validateSeries(series);
        if (windowSize <= 0) {
            throw new Error('Window size must be a positive number.');
        }
        if (series.values.length < windowSize) {
            return new RollingWindow([]);
        }

        const windows: number[][] = [];
        for (let i = 0; i <= series.values.length - windowSize; i++) {
            const window = series.values.slice(i, i + windowSize);
            windows.push(window);
        }
        return new RollingWindow(windows);
    }

    movingAverage(series: DataSeries, windowSize: number): number[] {
        return this.rolling(series, windowSize).mean();
    }

    // K-means wrapper (uses imported KMeans class)
    kmeans(matrix: DataMatrix, nClusters: number, options: KMeansOptions = {}): { clusters: number[][][], centroids: number[][] } {
        validateMatrix(matrix);
        const points: number[][] = matrix.data;

        // Use the new MiniBatchKMeans class
        const kmeans = new KMeans(points, nClusters, options);
        const result = kmeans.run();

        const centroids = result.clusters.map(c => (c as any).centroid);
        const clusters = result.clusters.map(c => (c as any).points);
        
        return { clusters, centroids };
    }

    // Time helper wrapper functions
    getWeekNumber(dateString: string): number {
        return getWeekNumber(dateString);
    }

    getSameWeekDayLastYear(dateString: string): string {
        return getSameWeekDayLastYear(dateString);
    }

    // ========================================
    // Prediction functions
    // ========================================

    timeSeriesForecast(series: DataSeries, forecastPeriods: number): ForecastResult {
        validateSeries(series);

        const model = calculateLinearRegression(series.values);
        const forecast = generateForecast(model, series.values.length, forecastPeriods);
        const predictionIntervals = calculatePredictionIntervals(series.values, model, forecast);
        
        return {
            forecast,
            predictionIntervals,
            modelParameters: {
                slope: model.slope,
                intercept: model.intercept,
            },
        };
    }
}

export const analytics = new AnalyticsEngine();