namespace JobTrackerApi.Services
{
    public enum PipelineCategory
    {
        Active,
        Success,
        Closed,
    }

    public sealed record PipelineStage(string Key, int Order, PipelineCategory Category);

    /// <summary>
    /// Canonical job-application pipeline: the single source of truth for the ordered set of
    /// statuses, their grouping, and how free-text/legacy values normalize onto them.
    /// Status remains a free-text column so custom values are never destroyed; this only
    /// canonicalizes casing and known synonyms.
    /// </summary>
    public static class JobPipeline
    {
        public const string DefaultStatus = "Applied";

        public static readonly IReadOnlyList<PipelineStage> Stages = new List<PipelineStage>
        {
            new("Applied", 1, PipelineCategory.Active),
            new("Waiting", 2, PipelineCategory.Active),
            new("Interview", 3, PipelineCategory.Active),
            new("Offer", 4, PipelineCategory.Success),
            new("Rejected", 5, PipelineCategory.Closed),
            new("Ghosted", 6, PipelineCategory.Closed),
        };

        private static readonly Dictionary<string, string> Canonical =
            Stages.ToDictionary(s => s.Key, s => s.Key, StringComparer.OrdinalIgnoreCase);

        // Legacy/synonym spellings that should collapse onto a canonical stage.
        private static readonly Dictionary<string, string> Aliases = new(StringComparer.OrdinalIgnoreCase)
        {
            ["interviewing"] = "Interview",
            ["interviews"] = "Interview",
            ["interviewed"] = "Interview",
            ["in interview"] = "Interview",
            ["awaiting response"] = "Waiting",
            ["awaiting"] = "Waiting",
            ["in progress"] = "Waiting",
            ["pending"] = "Waiting",
            ["no response"] = "Ghosted",
            ["no reply"] = "Ghosted",
            ["declined"] = "Rejected",
        };

        /// <summary>
        /// Returns the canonical status for a raw value: trims, matches a stage case-insensitively,
        /// or maps a known synonym. Unknown non-empty values are preserved (trimmed) so custom
        /// statuses survive. Empty/whitespace becomes the default stage.
        /// </summary>
        public static string Normalize(string? status)
        {
            var trimmed = (status ?? string.Empty).Trim();
            if (trimmed.Length == 0) return DefaultStatus;
            if (Canonical.TryGetValue(trimmed, out var canonical)) return canonical;
            if (Aliases.TryGetValue(trimmed, out var alias)) return alias;
            return trimmed;
        }

        public static bool IsCanonical(string? status)
            => !string.IsNullOrWhiteSpace(status) && Canonical.ContainsKey(status.Trim());

        public static int OrderOf(string? status)
        {
            var normalized = Normalize(status);
            var stage = Stages.FirstOrDefault(s => string.Equals(s.Key, normalized, StringComparison.OrdinalIgnoreCase));
            return stage?.Order ?? int.MaxValue; // custom statuses sort last
        }
    }
}