using EonaCat.DoxaApi.Models;

namespace EonaCat.DoxaApi.Generation
{
    // This file is part of the EonaCat project(s) which is released under the Apache License.
    // See the LICENSE file or go to https://EonaCat.com/license for full license details.

    /// <summary>
    /// Produces schema-shaped, deterministic-but-plausible fake JSON values for a given
    /// <see cref="SchemaModel"/>. Used by the built-in mock server so that frontend teams
    /// can develop against an API before its real implementation exists.
    /// </summary>
    public static class MockResponseGenerator
    {
        public static object? Generate(SchemaModel? schema, ApiDocument doc, int depth = 0, HashSet<string>? seen = null)
        {
            seen ??= new HashSet<string>();
            if (schema is null || depth > 8)
            {
                return null;
            }

            if (schema.RefName is not null)
            {
                if (!seen.Add(schema.RefName))
                {
                    return new Dictionary<string, object?>();
                }

                if (doc.Schemas.TryGetValue(schema.RefName, out var resolved))
                {
                    return Generate(resolved, doc, depth + 1, seen);
                }

                return new Dictionary<string, object?>();
            }

            switch (schema.Type)
            {
                case "string":
                    return MockString(schema.Format);
                case "integer":
                    return RandomInt(depth);
                case "number":
                    return Math.Round(RandomInt(depth) + 0.5, 2);
                case "boolean":
                    return depth % 2 == 0;
                case "enum":
                    return schema.EnumValues?.Count > 0 ? schema.EnumValues[0] : "value";
                case "array":
                    return new List<object?>
                    {
                        Generate(schema.Items, doc, depth + 1, seen),
                        Generate(schema.Items, doc, depth + 1, seen)
                    };
                case "object":
                    {
                        if (schema.Properties is null)
                        {
                            return new Dictionary<string, object?>();
                        }

                        var obj = new Dictionary<string, object?>();
                        foreach (var (key, propSchema) in schema.Properties)
                        {
                            obj[key] = Generate(propSchema, doc, depth + 1, seen);
                        }

                        return obj;
                    }
                default:
                    return null;
            }
        }

        private static object MockString(string? format) => format switch
        {
            "date-time" => DateTime.UtcNow.ToString("O"),
            "date" => DateOnly.FromDateTime(DateTime.UtcNow).ToString("yyyy-MM-dd"),
            "time" => TimeOnly.FromDateTime(DateTime.UtcNow).ToString("HH:mm:ss"),
            "uuid" => Guid.NewGuid().ToString(),
            "uri" => "https://example.com/resource",
            _ => "string"
        };

        private static int RandomInt(int depth) => 1 + depth;
    }
}