using System.Collections.Immutable;
using System.Web;

namespace StellaOps.Scanner.Analyzers.Lang.Bun.Internal;

/// <summary>
/// Represents a discovered Bun/npm package with evidence.
/// </summary>
internal sealed class BunPackage
{
    private readonly List<string> _occurrencePaths = [];

    private BunPackage(string name, string version)
    {
        Name = name;
        Version = version;
        Purl = BuildPurl(name, version);
        ComponentKey = $"purl::{Purl}";
    }

    public string Name { get; }
    public string Version { get; }
    public string Purl { get; }
    public string ComponentKey { get; }
    public string? Resolved { get; private init; }
    public string? Integrity { get; private init; }
    public string? Source { get; private init; }
    public bool IsPrivate { get; private init; }
    public bool IsDev { get; private init; }
    public bool IsOptional { get; private init; }
    public bool IsPeer { get; private init; }

    /// <summary>
    /// Source type: npm, git, tarball, file, link, workspace.
    /// </summary>
    public string SourceType { get; private init; } = "npm";

    /// <summary>
    /// Git commit hash for git dependencies.
    /// </summary>
    public string? GitCommit { get; private init; }

    /// <summary>
    /// Original specifier (e.g., "github:user/repo#tag").
    /// </summary>
    public string? Specifier { get; private init; }

    /// <summary>
    /// Direct dependencies of this package (for transitive analysis).
    /// </summary>
    public IReadOnlyList<string> Dependencies { get; private init; } = Array.Empty<string>();

    /// <summary>
    /// Whether this is a direct dependency (in root package.json) or transitive.
    /// </summary>
    public bool IsDirect { get; set; }

    /// <summary>
    /// Whether this package has been patched (via patchedDependencies or .patches directory).
    /// </summary>
    public bool IsPatched { get; set; }

    /// <summary>
    /// Path to the patch file if this package is patched.
    /// </summary>
    public string? PatchFile { get; set; }

    /// <summary>
    /// Custom registry URL if this package comes from a non-default registry.
    /// </summary>
    public string? CustomRegistry { get; set; }

    /// <summary>
    /// Logical path where this package was found (may be symlink).
    /// </summary>
    public string? LogicalPath { get; private init; }

    /// <summary>
    /// Real path after resolving symlinks.
    /// </summary>
    public string? RealPath { get; private init; }

    /// <summary>
    /// All filesystem paths where this package (name@version) was found.
    /// </summary>
    public IReadOnlyList<string> OccurrencePaths => _occurrencePaths.ToImmutableArray();

    public void AddOccurrence(string path)
    {
        if (!string.IsNullOrWhiteSpace(path) && !_occurrencePaths.Contains(path, StringComparer.Ordinal))
        {
            _occurrencePaths.Add(path);
        }
    }

    public static BunPackage FromPackageJson(
        string name,
        string version,
        string logicalPath,
        string? realPath,
        bool isPrivate,
        BunLockEntry? lockEntry)
    {
        return new BunPackage(name, version)
        {
            LogicalPath = logicalPath,
            RealPath = realPath,
            IsPrivate = isPrivate,
            Source = "node_modules",
            Resolved = lockEntry?.Resolved,
            Integrity = lockEntry?.Integrity,
            IsDev = lockEntry?.IsDev ?? false,
            IsOptional = lockEntry?.IsOptional ?? false,
            IsPeer = lockEntry?.IsPeer ?? false,
            SourceType = lockEntry?.SourceType ?? "npm",
            GitCommit = lockEntry?.GitCommit,
            Specifier = lockEntry?.Specifier,
            Dependencies = lockEntry?.Dependencies ?? Array.Empty<string>()
        };
    }

    public static BunPackage FromLockEntry(BunLockEntry entry, string source)
    {
        ArgumentNullException.ThrowIfNull(entry);

        return new BunPackage(entry.Name, entry.Version)
        {
            Source = source,
            Resolved = entry.Resolved,
            Integrity = entry.Integrity,
            IsDev = entry.IsDev,
            IsOptional = entry.IsOptional,
            IsPeer = entry.IsPeer,
            SourceType = entry.SourceType,
            GitCommit = entry.GitCommit,
            Specifier = entry.Specifier,
            Dependencies = entry.Dependencies
        };
    }

    public IEnumerable<KeyValuePair<string, string?>> CreateMetadata()
    {
        var metadata = new SortedDictionary<string, string?>(StringComparer.Ordinal);

        if (!string.IsNullOrEmpty(LogicalPath))
        {
            metadata["path"] = NormalizePath(LogicalPath);
        }

        if (!string.IsNullOrEmpty(RealPath) && RealPath != LogicalPath)
        {
            metadata["realPath"] = NormalizePath(RealPath);
        }

        if (!string.IsNullOrEmpty(Source))
        {
            metadata["source"] = Source;
        }

        if (!string.IsNullOrEmpty(Resolved))
        {
            metadata["resolved"] = Resolved;
        }

        if (!string.IsNullOrEmpty(Integrity))
        {
            metadata["integrity"] = Integrity;
        }

        if (IsPrivate)
        {
            metadata["private"] = "true";
        }

        if (!string.IsNullOrEmpty(CustomRegistry))
        {
            metadata["customRegistry"] = CustomRegistry;
        }

        if (IsDev)
        {
            metadata["dev"] = "true";
        }

        if (IsDirect)
        {
            metadata["direct"] = "true";
        }

        if (!string.IsNullOrEmpty(GitCommit))
        {
            metadata["gitCommit"] = GitCommit;
        }

        if (IsOptional)
        {
            metadata["optional"] = "true";
        }

        metadata["packageManager"] = "bun";

        if (IsPatched)
        {
            metadata["patched"] = "true";
        }

        if (!string.IsNullOrEmpty(PatchFile))
        {
            metadata["patchFile"] = NormalizePath(PatchFile);
        }

        if (IsPeer)
        {
            metadata["peer"] = "true";
        }

        if (SourceType != "npm")
        {
            metadata["sourceType"] = SourceType;
        }

        if (!string.IsNullOrEmpty(Specifier))
        {
            metadata["specifier"] = Specifier;
        }

        if (_occurrencePaths.Count > 1)
        {
            metadata["occurrences"] = string.Join(";", _occurrencePaths.Select(NormalizePath).Order(StringComparer.Ordinal));
        }

        return metadata;
    }

    public IEnumerable<LanguageComponentEvidence> CreateEvidence()
    {
        var evidence = new List<LanguageComponentEvidence>();

        if (!string.IsNullOrEmpty(LogicalPath))
        {
            evidence.Add(new LanguageComponentEvidence(
                LanguageEvidenceKind.File,
                Source ?? "node_modules",
                NormalizePath(Path.Combine(LogicalPath, "package.json")),
                null,
                null));
        }

        if (!string.IsNullOrEmpty(Resolved))
        {
            evidence.Add(new LanguageComponentEvidence(
                LanguageEvidenceKind.Metadata,
                "resolved",
                "bun.lock",
                Resolved,
                null));
        }

        if (!string.IsNullOrEmpty(Integrity))
        {
            evidence.Add(new LanguageComponentEvidence(
                LanguageEvidenceKind.Metadata,
                "integrity",
                "bun.lock",
                Integrity,
                null));
        }

        return evidence;
    }

    private static string BuildPurl(string name, string version)
    {
        // pkg:npm/<name>@<version>
        // Scoped packages: @scope/name → %40scope/name
        var encodedName = name.StartsWith('@')
            ? $"%40{HttpUtility.UrlEncode(name[1..]).Replace("%2f", "/", StringComparison.OrdinalIgnoreCase)}"
            : HttpUtility.UrlEncode(name);

        return $"pkg:npm/{encodedName}@{version}";
    }

    private static string NormalizePath(string path)
    {
        // Normalize to forward slashes for cross-platform consistency
        return path.Replace('\\', '/');
    }
}