// <copyright file="CoberturaParser.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under AGPL-3.0-or-later.
// </copyright>
// Sprint: SPRINT_20260105_002_005_TEST_cross_cutting
// Task: CCUT-014

using System.Collections.Immutable;
using System.Globalization;
using System.Xml.Linq;

namespace StellaOps.Testing.Coverage;

/// <summary>
/// Parses Cobertura XML coverage reports.
/// </summary>
public static class CoberturaParser
{
    /// <summary>
    /// Parse a Cobertura XML file.
    /// </summary>
    /// <param name="filePath">Path to Cobertura XML file.</param>
    /// <param name="ct">Cancellation token.</param>
    /// <returns>Parsed coverage report.</returns>
    public static async Task<CoverageReport> ParseFileAsync(string filePath, CancellationToken ct = default)
    {
        var xml = await File.ReadAllTextAsync(filePath, ct);
        return Parse(xml);
    }

    /// <summary>
    /// Parse a Cobertura XML string.
    /// </summary>
    /// <param name="xml">Cobertura XML content.</param>
    /// <returns>Parsed coverage report.</returns>
    public static CoverageReport Parse(string xml)
    {
        var doc = XDocument.Parse(xml);
        var coverage = doc.Root ?? throw new InvalidOperationException("Invalid Cobertura XML: no root element");

        var files = new List<FileCoverage>();

        // Parse overall coverage
        var lineCoverage = ParseDecimal(coverage.Attribute("line-rate")?.Value ?? "0");
        var branchCoverage = ParseDecimal(coverage.Attribute("branch-rate")?.Value ?? "0");

        // Parse timestamp
        var timestamp = coverage.Attribute("timestamp")?.Value;
        var generatedAt = timestamp != null
            ? DateTimeOffset.FromUnixTimeSeconds(long.Parse(timestamp, CultureInfo.InvariantCulture))
            : DateTimeOffset.UtcNow;

        // Parse packages -> classes -> files
        foreach (var package in coverage.Descendants("package"))
        {
            foreach (var cls in package.Descendants("class"))
            {
                var fileCoverage = ParseClass(cls);
                if (fileCoverage != null)
                {
                    files.Add(fileCoverage);
                }
            }
        }

        return new CoverageReport(
            Files: [.. files],
            OverallLineCoverage: lineCoverage,
            OverallBranchCoverage: branchCoverage,
            GeneratedAt: generatedAt);
    }

    private static FileCoverage? ParseClass(XElement cls)
    {
        var filename = cls.Attribute("filename")?.Value;
        if (string.IsNullOrEmpty(filename))
        {
            return null;
        }

        var lineCoverage = ParseDecimal(cls.Attribute("line-rate")?.Value ?? "0");
        var branchCoverage = ParseDecimal(cls.Attribute("branch-rate")?.Value ?? "0");

        var lines = new List<LineCoverageData>();
        var branches = new List<BranchCoverageData>();

        var linesElement = cls.Element("lines");
        if (linesElement != null)
        {
            foreach (var line in linesElement.Elements("line"))
            {
                var lineNumber = int.Parse(line.Attribute("number")?.Value ?? "0", CultureInfo.InvariantCulture);
                var hits = int.Parse(line.Attribute("hits")?.Value ?? "0", CultureInfo.InvariantCulture);
                var isBranch = line.Attribute("branch")?.Value == "true";

                lines.Add(new LineCoverageData(
                    LineNumber: lineNumber,
                    HitCount: hits,
                    IsCoverable: true));

                // Parse branch conditions if present
                if (isBranch)
                {
                    var conditionCoverage = line.Attribute("condition-coverage")?.Value;
                    var conditions = line.Element("conditions");

                    if (conditions != null)
                    {
                        var branchIndex = 0;
                        foreach (var condition in conditions.Elements("condition"))
                        {
                            var coverage = int.Parse(
                                condition.Attribute("coverage")?.Value ?? "0",
                                CultureInfo.InvariantCulture);

                            branches.Add(new BranchCoverageData(
                                Line: lineNumber,
                                BranchId: $"{lineNumber}-{branchIndex}",
                                Type: condition.Attribute("type")?.Value ?? "branch",
                                HitCount: coverage > 0 ? 1 : 0));

                            branchIndex++;
                        }
                    }
                    else if (conditionCoverage != null)
                    {
                        // Parse condition-coverage like "50% (1/2)"
                        var parts = conditionCoverage.Split(['(', '/', ')'], StringSplitOptions.RemoveEmptyEntries);
                        if (parts.Length >= 2)
                        {
                            var covered = int.Parse(parts[0].TrimEnd('%'), CultureInfo.InvariantCulture);
                            var total = int.Parse(parts[1], CultureInfo.InvariantCulture);

                            for (int i = 0; i < total; i++)
                            {
                                branches.Add(new BranchCoverageData(
                                    Line: lineNumber,
                                    BranchId: $"{lineNumber}-{i}",
                                    Type: "branch",
                                    HitCount: i < (covered * total / 100) ? 1 : 0));
                            }
                        }
                    }
                }
            }
        }

        return new FileCoverage(
            Path: filename,
            LineCoverage: lineCoverage,
            BranchCoverage: branchCoverage,
            Lines: [.. lines],
            Branches: [.. branches]);
    }

    private static decimal ParseDecimal(string value)
    {
        if (decimal.TryParse(value, NumberStyles.Float, CultureInfo.InvariantCulture, out var result))
        {
            return result;
        }

        return 0m;
    }
}