// <copyright file="Spdx3Document.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under the BUSL-1.1.
// </copyright>


using StellaOps.Spdx3.Model.Software;
using System.Collections.Immutable;

namespace StellaOps.Spdx3.Model;

/// <summary>
/// Represents a parsed SPDX 3.0.1 document containing all elements.
/// </summary>
public sealed class Spdx3Document
{
    private readonly Dictionary<string, Spdx3Element> _elementsById;
    private readonly Dictionary<string, Spdx3CreationInfo> _creationInfoById;

    /// <summary>
    /// Initializes a new instance of the <see cref="Spdx3Document"/> class.
    /// </summary>
    /// <param name="elements">All elements in the document.</param>
    /// <param name="creationInfos">All CreationInfo objects.</param>
    /// <param name="profiles">Detected profile conformance.</param>
    /// <param name="spdxDocument">The root SpdxDocument element if present.</param>
    public Spdx3Document(
        IEnumerable<Spdx3Element> elements,
        IEnumerable<Spdx3CreationInfo> creationInfos,
        IEnumerable<Spdx3ProfileIdentifier> profiles,
        Spdx3SpdxDocument? spdxDocument = null)
    {
        var elementList = elements.ToList();
        
        // Use GroupBy to handle duplicates - last element wins for lookup but keeps all for validation
        _elementsById = elementList
            .GroupBy(e => e.SpdxId, StringComparer.Ordinal)
            .ToDictionary(g => g.Key, g => g.Last(), StringComparer.Ordinal);
        
        _creationInfoById = creationInfos
            .Where(c => c.Id != null)
            .GroupBy(c => c.Id!, StringComparer.Ordinal)
            .ToDictionary(g => g.Key, g => g.Last(), StringComparer.Ordinal);
        
        Profiles = profiles.ToImmutableHashSet();
        SpdxDocument = spdxDocument;
        
        // Categorize elements by type - use original list to preserve duplicates for counting
        Packages = elementList.OfType<Spdx3Package>().ToImmutableArray();
        Files = elementList.OfType<Spdx3File>().ToImmutableArray();
        Snippets = elementList.OfType<Spdx3Snippet>().ToImmutableArray();
        Relationships = elementList.OfType<Spdx3Relationship>().ToImmutableArray();
        AllElements = elementList.ToImmutableArray();
    }

    /// <summary>
    /// Gets all elements including duplicates (for validation).
    /// </summary>
    public ImmutableArray<Spdx3Element> AllElements { get; }

    /// <summary>
    /// Gets the root SpdxDocument element if present.
    /// </summary>
    public Spdx3SpdxDocument? SpdxDocument { get; }

    /// <summary>
    /// Gets all elements in the document.
    /// </summary>
    public IReadOnlyCollection<Spdx3Element> Elements => _elementsById.Values;

    /// <summary>
    /// Gets all packages in the document.
    /// </summary>
    public ImmutableArray<Spdx3Package> Packages { get; }

    /// <summary>
    /// Gets all files in the document.
    /// </summary>
    public ImmutableArray<Spdx3File> Files { get; }

    /// <summary>
    /// Gets all snippets in the document.
    /// </summary>
    public ImmutableArray<Spdx3Snippet> Snippets { get; }

    /// <summary>
    /// Gets all relationships in the document.
    /// </summary>
    public ImmutableArray<Spdx3Relationship> Relationships { get; }

    /// <summary>
    /// Gets the detected profile conformance.
    /// </summary>
    public ImmutableHashSet<Spdx3ProfileIdentifier> Profiles { get; }

    /// <summary>
    /// Gets all creation info objects in the document.
    /// </summary>
    public IReadOnlyCollection<Spdx3CreationInfo> CreationInfos => _creationInfoById.Values;

    /// <summary>
    /// Gets an element by its SPDX ID.
    /// </summary>
    /// <param name="spdxId">The SPDX ID.</param>
    /// <returns>The element, or null if not found.</returns>
    public Spdx3Element? GetById(string spdxId)
    {
        return _elementsById.TryGetValue(spdxId, out var element) ? element : null;
    }

    /// <summary>
    /// Gets an element by its SPDX ID as a specific type.
    /// </summary>
    /// <typeparam name="T">The element type.</typeparam>
    /// <param name="spdxId">The SPDX ID.</param>
    /// <returns>The element, or null if not found or wrong type.</returns>
    public T? GetById<T>(string spdxId) where T : Spdx3Element
    {
        return GetById(spdxId) as T;
    }

    /// <summary>
    /// Gets a CreationInfo by its ID.
    /// </summary>
    /// <param name="id">The CreationInfo ID.</param>
    /// <returns>The CreationInfo, or null if not found.</returns>
    public Spdx3CreationInfo? GetCreationInfo(string id)
    {
        return _creationInfoById.TryGetValue(id, out var info) ? info : null;
    }

    /// <summary>
    /// Gets relationships where the given element is the source.
    /// </summary>
    /// <param name="spdxId">The source element ID.</param>
    /// <returns>Matching relationships.</returns>
    public IEnumerable<Spdx3Relationship> GetRelationshipsFrom(string spdxId)
    {
        return Relationships.Where(r => r.From == spdxId);
    }

    /// <summary>
    /// Gets relationships where the given element is a target.
    /// </summary>
    /// <param name="spdxId">The target element ID.</param>
    /// <returns>Matching relationships.</returns>
    public IEnumerable<Spdx3Relationship> GetRelationshipsTo(string spdxId)
    {
        return Relationships.Where(r => r.To.Contains(spdxId));
    }

    /// <summary>
    /// Gets direct dependencies of a package.
    /// </summary>
    /// <param name="packageId">The package SPDX ID.</param>
    /// <returns>Dependent packages.</returns>
    public IEnumerable<Spdx3Package> GetDependencies(string packageId)
    {
        return GetRelationshipsFrom(packageId)
            .Where(r => r.RelationshipType == Spdx3RelationshipType.DependsOn)
            .SelectMany(r => r.To)
            .Select(GetById<Spdx3Package>)
            .Where(p => p != null)
            .Cast<Spdx3Package>();
    }

    /// <summary>
    /// Gets all files contained in a package.
    /// </summary>
    /// <param name="packageId">The package SPDX ID.</param>
    /// <returns>Contained files.</returns>
    public IEnumerable<Spdx3File> GetContainedFiles(string packageId)
    {
        return GetRelationshipsFrom(packageId)
            .Where(r => r.RelationshipType == Spdx3RelationshipType.Contains)
            .SelectMany(r => r.To)
            .Select(GetById<Spdx3File>)
            .Where(f => f != null)
            .Cast<Spdx3File>();
    }

    /// <summary>
    /// Checks if the document conforms to a specific profile.
    /// </summary>
    /// <param name="profile">The profile to check.</param>
    /// <returns>True if the document conforms.</returns>
    public bool ConformsTo(Spdx3ProfileIdentifier profile)
    {
        return Profiles.Contains(profile);
    }

    /// <summary>
    /// Gets all PURLs from packages in the document.
    /// </summary>
    /// <returns>Package URLs.</returns>
    public IEnumerable<string> GetAllPurls()
    {
        return Packages
            .SelectMany(p => p.ExternalIdentifier)
            .Where(i => i.ExternalIdentifierType == Spdx3ExternalIdentifierType.PackageUrl)
            .Select(i => i.Identifier)
            .Distinct(StringComparer.Ordinal);
    }

    /// <summary>
    /// Gets the root package (if any).
    /// </summary>
    /// <returns>The root package, or null.</returns>
    public Spdx3Package? GetRootPackage()
    {
        if (SpdxDocument?.RootElement.Length > 0)
        {
            var rootId = SpdxDocument.RootElement[0];
            return GetById<Spdx3Package>(rootId);
        }

        // Fallback: find package with no incoming Contains relationships
        var containedIds = Relationships
            .Where(r => r.RelationshipType == Spdx3RelationshipType.Contains)
            .SelectMany(r => r.To)
            .ToHashSet(StringComparer.Ordinal);

        return Packages.FirstOrDefault(p => !containedIds.Contains(p.SpdxId));
    }
}