using System.Text.Json;
using System.Text.Json.Serialization;
using w4c_workflows.Models;

namespace w4c_workflows.Services.Triggers;

/// <summary>
/// Typed trigger model parsed from <c>Workflow.TriggerJson</c>. The compiler
/// stores the trigger exactly as it appeared in YAML (camelCase, nulls omitted);
/// this record normalizes it for the trigger engine: the interval string becomes
/// a parsed <see cref="TimeSpan"/> and the type is guaranteed non-null.
/// </summary>
public sealed record TriggerSpec(
    string Type,
    string? Cron,
    TimeSpan? Interval,
    string? WebhookPath,
    string? Stream)
{
    private static readonly JsonSerializerOptions Json = new(JsonSerializerDefaults.Web)
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
    };

    /// <summary>
    /// Parses stored trigger JSON. Returns null (with a non-null
    /// <paramref name="error"/>) when the JSON is absent, malformed, or the
    /// trigger lacks a valid type/interval.
    /// </summary>
    public static TriggerSpec? Parse(string? json, out string? error)
    {
        error = null;
        if (string.IsNullOrWhiteSpace(json))
            return null;

        TriggerDefinition def;
        try
        {
            def = JsonSerializer.Deserialize<TriggerDefinition>(json, Json) ?? new TriggerDefinition();
        }
        catch (JsonException ex)
        {
            error = ex.Message;
            return null;
        }

        if (string.IsNullOrWhiteSpace(def.Type))
        {
            error = "trigger.type is missing";
            return null;
        }

        TimeSpan? interval = null;
        if (!string.IsNullOrWhiteSpace(def.Interval))
        {
            if (!DurationParser.TryParse(def.Interval, out var parsed))
            {
                error = $"trigger.interval '{def.Interval}' is not a valid duration";
                return null;
            }
            interval = parsed;
        }

        return new TriggerSpec(def.Type, def.Cron, interval, def.WebhookPath, def.Stream);
    }
}