// <copyright file="CycloneDxEvidenceMapper.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under the AGPL-3.0-or-later.
// </copyright>

using System.Collections.Immutable;
using CycloneDX.Models;
using StellaOps.Scanner.Core.Contracts;

namespace StellaOps.Scanner.Emit.Evidence;

/// <summary>
/// Maps StellaOps evidence data to CycloneDX 1.7 native evidence fields.
/// Sprint: SPRINT_20260107_005_001 Task EV-001
/// </summary>
/// <remarks>
/// This mapper replaces the legacy property-based evidence storage with
/// native CycloneDX 1.7 evidence structures for spec compliance.
/// </remarks>
public sealed class CycloneDxEvidenceMapper
{
    private readonly IdentityEvidenceBuilder _identityBuilder;
    private readonly OccurrenceEvidenceBuilder _occurrenceBuilder;
    private readonly LicenseEvidenceBuilder _licenseBuilder;

    /// <summary>
    /// Initializes a new instance of the <see cref="CycloneDxEvidenceMapper"/> class.
    /// </summary>
    public CycloneDxEvidenceMapper()
    {
        _identityBuilder = new IdentityEvidenceBuilder();
        _occurrenceBuilder = new OccurrenceEvidenceBuilder();
        _licenseBuilder = new LicenseEvidenceBuilder();
    }

    /// <summary>
    /// Maps component evidence to CycloneDX 1.7 Evidence structure.
    /// </summary>
    /// <param name="component">The aggregated component with evidence data.</param>
    /// <returns>The mapped CycloneDX Evidence, or null if no evidence available.</returns>
    public CycloneDX.Models.Evidence? Map(AggregatedComponent component)
    {
        ArgumentNullException.ThrowIfNull(component);

        var identity = _identityBuilder.Build(component);
        var occurrences = _occurrenceBuilder.Build(component);
        var licenses = _licenseBuilder.Build(component);
        var copyrights = BuildCopyrightEvidence(component);

        if (identity is null && occurrences.IsDefaultOrEmpty && licenses.IsDefaultOrEmpty && copyrights.IsDefaultOrEmpty)
        {
            return null;
        }

        return new CycloneDX.Models.Evidence
        {
            Identity = identity is not null ? [ConvertToEvidenceIdentity(identity)] : null,
            Occurrences = occurrences.IsDefaultOrEmpty ? null : ConvertToEvidenceOccurrences(occurrences),
            Licenses = licenses.IsDefaultOrEmpty ? null : ConvertToLicenseChoices(licenses),
            Copyright = copyrights.IsDefaultOrEmpty ? null : ConvertToEvidenceCopyrights(copyrights),
        };
    }

    private static EvidenceIdentity ConvertToEvidenceIdentity(ComponentIdentityEvidence identity)
    {
        return new EvidenceIdentity
        {
            // EvidenceIdentity.Field is a string in some CycloneDX versions
            Confidence = (float?)identity.Confidence,
            ConcludedValue = identity.Field,
            Methods = identity.Methods?.Select(m => new EvidenceMethods
            {
                Confidence = (float?)m.Confidence ?? 0f,
                Value = m.Value,
            }).ToList(),
        };
    }

    private static List<EvidenceOccurrence> ConvertToEvidenceOccurrences(ImmutableArray<OccurrenceEvidence> occurrences)
    {
        return occurrences.Select(o => new EvidenceOccurrence
        {
            Location = o.Location,
        }).ToList();
    }

    private static List<LicenseChoice> ConvertToLicenseChoices(ImmutableArray<LicenseEvidence> licenses)
    {
        return licenses.Select(l => l.License).ToList();
    }

    private static List<EvidenceCopyright> ConvertToEvidenceCopyrights(ImmutableArray<CopyrightEvidence> copyrights)
    {
        return copyrights.Select(c => new EvidenceCopyright
        {
            Text = c.Text,
        }).ToList();
    }

    /// <summary>
    /// Maps legacy property-based evidence to component evidence data.
    /// </summary>
    /// <param name="properties">Legacy properties containing evidence data.</param>
    /// <returns>Parsed evidence records.</returns>
    public static ImmutableArray<ComponentEvidenceRecord> ParseLegacyProperties(
        IReadOnlyList<Property>? properties)
    {
        if (properties is null || properties.Count == 0)
        {
            return ImmutableArray<ComponentEvidenceRecord>.Empty;
        }

        var results = ImmutableArray.CreateBuilder<ComponentEvidenceRecord>();

        foreach (var prop in properties)
        {
            if (prop.Name?.StartsWith("stellaops:evidence[", StringComparison.OrdinalIgnoreCase) == true &&
                !string.IsNullOrWhiteSpace(prop.Value))
            {
                var parsed = ParseLegacyEvidenceValue(prop.Value);
                if (parsed is not null)
                {
                    results.Add(parsed);
                }
            }
        }

        return results.ToImmutable();
    }

    private static ComponentEvidenceRecord? ParseLegacyEvidenceValue(string value)
    {
        // Format: kind:value@source (e.g., "crypto:aes-256@/src/crypto.c")
        var atIndex = value.LastIndexOf('@');
        if (atIndex <= 0)
        {
            return null;
        }

        var kindValue = value[..atIndex];
        var source = value[(atIndex + 1)..];

        var colonIndex = kindValue.IndexOf(':');
        if (colonIndex <= 0)
        {
            return null;
        }

        var kind = kindValue[..colonIndex];
        var evidenceValue = kindValue[(colonIndex + 1)..];

        return new ComponentEvidenceRecord
        {
            Kind = kind,
            Value = evidenceValue,
            Source = source,
        };
    }

    private static ImmutableArray<CopyrightEvidence> BuildCopyrightEvidence(AggregatedComponent component)
    {
        if (component.Evidence.IsDefaultOrEmpty)
        {
            return ImmutableArray<CopyrightEvidence>.Empty;
        }

        var copyrightEvidence = component.Evidence
            .Where(e => string.Equals(e.Kind, "copyright", StringComparison.OrdinalIgnoreCase))
            .Select(e => new CopyrightEvidence { Text = e.Value })
            .ToImmutableArray();

        return copyrightEvidence;
    }
}

/// <summary>
/// Represents a parsed component evidence record from legacy or native formats.
/// Sprint: SPRINT_20260107_005_001 Task EV-001
/// </summary>
public sealed record ComponentEvidenceRecord
{
    /// <summary>
    /// Gets or sets the kind of evidence (e.g., "crypto", "license", "copyright").
    /// </summary>
    public required string Kind { get; init; }

    /// <summary>
    /// Gets or sets the evidence value (e.g., algorithm name, license ID).
    /// </summary>
    public required string Value { get; init; }

    /// <summary>
    /// Gets or sets the source location of the evidence.
    /// </summary>
    public required string Source { get; init; }

    /// <summary>
    /// Gets or sets the confidence score (0.0-1.0).
    /// </summary>
    public double? Confidence { get; init; }

    /// <summary>
    /// Gets or sets the detection technique used.
    /// </summary>
    public string? Technique { get; init; }
}

/// <summary>
/// StellaOps internal Copyright Evidence model.
/// Sprint: SPRINT_20260107_005_001 Task EV-001
/// </summary>
public sealed class CopyrightEvidence
{
    /// <summary>
    /// Gets or sets the copyright text.
    /// </summary>
    public string? Text { get; set; }
}