using Explorer.Domain;

namespace Explorer.Application;

public static class GitListingOverlay
{
    public static string ForNestedRepo(GitStatus status)
    {
        var parts = new List<string> { status.Branch };
        if (!string.IsNullOrEmpty(status.OperationLabel))
        {
            parts.Add(status.OperationLabel);
        }

        if (status.ModifiedCount > 0)
        {
            parts.Add($"{status.ModifiedCount} modified");
        }

        if (status.UntrackedCount > 0)
        {
            parts.Add($"{status.UntrackedCount} untracked");
        }

        return string.Join(" · ", parts);
    }

    public static string ForItem(string itemFullPath, bool isDirectory, string repoRoot, GitStatus status)
    {
        var rel = ToGitRelative(repoRoot, itemFullPath);
        if (rel is null)
        {
            return "";
        }

        return isDirectory ? FolderLabel(status.Changes, rel) : FileLabel(status.Changes, rel);
    }

    internal static string? ToGitRelative(string repoRoot, string fullPath)
    {
        var root = PathRules.FromExtended(repoRoot).TrimEnd('\\');
        var full = PathRules.FromExtended(fullPath).TrimEnd('\\');
        if (full.Equals(root, StringComparison.OrdinalIgnoreCase))
        {
            return "";
        }

        if (!full.StartsWith(root + "\\", StringComparison.OrdinalIgnoreCase))
        {
            return null;
        }

        return full[(root.Length + 1)..].Replace('\\', '/');
    }

    private static string FileLabel(IReadOnlyList<GitChange> changes, string rel)
    {
        if (rel.Length == 0)
        {
            return "";
        }

        var hits = changes.Where(c => Matches(c, rel)).ToList();
        if (hits.Count == 0)
        {
            return "";
        }

        if (hits.Exists(c => c.State == GitChangeState.Unmerged))
        {
            return "Unmerged";
        }

        if (hits.Exists(c => c.State == GitChangeState.Untracked))
        {
            return "Untracked";
        }

        var staged = hits.Find(c => c.State == GitChangeState.Staged);
        var unstaged = hits.Find(c => c.State == GitChangeState.Unstaged);
        if (staged is not null && unstaged is not null)
        {
            return "Staged · Modified";
        }

        if (staged is not null)
        {
            return staged.Index switch
            {
                'R' => "Renamed",
                'A' => "Added",
                'D' => "Deleted",
                _ => "Staged"
            };
        }

        return unstaged is null ? "" : Title(unstaged.ChangeLabel);
    }

    private static string FolderLabel(IReadOnlyList<GitChange> changes, string rel)
    {
        var hits = changes.Where(c => Under(c, rel)).ToList();
        if (hits.Count == 0)
        {
            return "";
        }

        if (hits.Exists(c => c.State == GitChangeState.Unmerged))
        {
            return "Unmerged";
        }

        if (hits.TrueForAll(c => c.State == GitChangeState.Untracked))
        {
            return "Untracked";
        }

        return "Modified";
    }

    private static bool Matches(GitChange change, string rel)
        => Same(change.Path, rel)
           || (change.OriginalPath is { Length: > 0 } original && Same(original, rel));

    private static bool Under(GitChange change, string rel)
    {
        if (Matches(change, rel))
        {
            return true;
        }

        if (rel.Length == 0)
        {
            return true;
        }

        var prefix = rel + "/";
        return change.Path.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)
               || (change.OriginalPath is { Length: > 0 } original
                   && original.StartsWith(prefix, StringComparison.OrdinalIgnoreCase));
    }

    private static bool Same(string left, string right)
        => left.Equals(right, StringComparison.OrdinalIgnoreCase);

    private static string Title(string value)
        => string.IsNullOrEmpty(value) ? "" : char.ToUpperInvariant(value[0]) + value[1..];
}