using System.Text.Json;
using System.Text.Json.Serialization;
using Nexus.Api.Data;
using Nexus.Api.Integrations;

namespace Nexus.Api.Services;

public sealed record AgentConfig
{
    [JsonPropertyName("id")]
    public string Id { get; init; } = string.Empty;

    [JsonPropertyName("name")]
    public string Name { get; init; } = string.Empty;

    [JsonPropertyName("workspace")]
    public string? Workspace { get; init; }

    [JsonPropertyName("agentDir")]
    public string? AgentDir { get; init; }

    [JsonPropertyName("model")]
    [JsonConverter(typeof(AgentModelConfigConverter))]
    public AgentModelConfig? Model { get; init; }

    [JsonPropertyName("identity")]
    public AgentIdentityConfig? Identity { get; init; }

    [JsonPropertyName("subagents")]
    public SubAgentConfig? Subagents { get; init; }
}

public sealed record SubAgentConfig
{
    [JsonPropertyName("allowAgents")]
    public IReadOnlyList<string>? AllowAgents { get; init; }
}

public sealed record AgentIdentityConfig
{
    [JsonPropertyName("name")]
    public string Name { get; init; } = string.Empty;

    [JsonPropertyName("theme")]
    public string Theme { get; init; } = string.Empty;
}

public sealed record AgentModelConfig
{
    [JsonPropertyName("primary")]
    public string? Primary { get; init; }
}

public sealed class AgentModelConfigConverter : JsonConverter<AgentModelConfig>
{
    public override AgentModelConfig? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        if (reader.TokenType == JsonTokenType.Null)
            return null;

        if (reader.TokenType == JsonTokenType.String)
        {
            var primary = reader.GetString();
            return string.IsNullOrWhiteSpace(primary) ? null : new AgentModelConfig { Primary = primary };
        }

        if (reader.TokenType != JsonTokenType.StartObject)
            throw new JsonException("Agent model must be either a string or an object.");

        using var document = JsonDocument.ParseValue(ref reader);
        var root = document.RootElement;

        string? primary = null;
        foreach (var property in root.EnumerateObject())
        {
            if (!string.Equals(property.Name, "primary", StringComparison.OrdinalIgnoreCase))
                continue;

            primary = property.Value.ValueKind switch
            {
                JsonValueKind.String => property.Value.GetString(),
                JsonValueKind.Null => null,
                _ => throw new JsonException("Agent model primary must be a string.")
            };
            break;
        }

        return new AgentModelConfig { Primary = primary };
    }

    public override void Write(Utf8JsonWriter writer, AgentModelConfig value, JsonSerializerOptions options)
    {
        writer.WriteStartObject();
        if (!string.IsNullOrWhiteSpace(value.Primary))
            writer.WriteString("primary", value.Primary);
        else
            writer.WriteNull("primary");
        writer.WriteEndObject();
    }
}

public sealed record AgentInfo(
    string Id,
    string Name,
    string Role,
    string Model,
    OperationalStatus Status,
    DateTimeOffset? LastSeen,
    string? Workspace,
    string? Description
);

public sealed record AgentDetail(
    string Id,
    string Name,
    string Role,
    string Model,
    OperationalStatus Status,
    DateTimeOffset? LastSeen,
    string? Workspace,
    string? AgentDir,
    string? Description,
    IReadOnlyList<string>? SubAgents,
    string? IdentityName
);

public interface IAgentService
{
    Task<IReadOnlyCollection<AgentInfo>> GetAgentsAsync(CancellationToken cancellationToken);
    Task<AgentDetail?> GetAgentAsync(string id, CancellationToken cancellationToken);
    Task<IReadOnlySet<string>> GetAllowedAgentIdsAsync(CancellationToken cancellationToken);
}

public sealed class AgentService(IConfiguration configuration, IAgentRuntime runtime) : IAgentService
{
    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNameCaseInsensitive = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase
    };

    public async Task<IReadOnlyCollection<AgentInfo>> GetAgentsAsync(CancellationToken cancellationToken)
    {
        var configs = await LoadAgentConfigsAsync(cancellationToken);
        var runtimeStatus = await runtime.GetStatusAsync(cancellationToken);
        var overallOperational = runtimeStatus.Status;

        var now = DateTimeOffset.UtcNow;
        var agents = new List<AgentInfo>(configs.Count);
        foreach (var config in configs)
        {
            var model = ResolveModel(config);
            var role = DeriveRole(config.Id);
            var description = config.Identity?.Theme ?? string.Empty;

            if (string.IsNullOrEmpty(description))
            {
                description = config.Id switch
                {
                    "main" => "Primary conversational agent — routing and general-purpose chat",
                    _ => description
                };
            }

            agents.Add(new AgentInfo(
                Id: config.Id,
                Name: config.Identity?.Name ?? config.Name ?? config.Id,
                Role: role,
                Model: model,
                Status: overallOperational,
                LastSeen: now,
                Workspace: config.Workspace,
                Description: description
            ));
        }

        return agents.AsReadOnly();
    }

    public async Task<AgentDetail?> GetAgentAsync(string id, CancellationToken cancellationToken)
    {
        var configs = await LoadAgentConfigsAsync(cancellationToken);
        var config = configs.FirstOrDefault(a =>
            a.Id.Equals(id, StringComparison.OrdinalIgnoreCase));
        if (config is null) return null;

        var runtimeStatus = await runtime.GetStatusAsync(cancellationToken);
        var now = DateTimeOffset.UtcNow;
        var role = DeriveRole(config.Id);
        var description = config.Identity?.Theme ?? string.Empty;

        if (string.IsNullOrEmpty(description) && config.Id == "main")
            description = "Primary conversational agent — routing and general-purpose chat";

        return new AgentDetail(
            Id: config.Id,
            Name: config.Identity?.Name ?? config.Name ?? config.Id,
            Role: role,
            Model: ResolveModel(config),
            Status: runtimeStatus.Status,
            LastSeen: now,
            Workspace: config.Workspace,
            AgentDir: config.AgentDir,
            Description: description,
            SubAgents: config.Subagents?.AllowAgents,
            IdentityName: config.Identity?.Name
        );
    }


    public async Task<IReadOnlySet<string>> GetAllowedAgentIdsAsync(CancellationToken cancellationToken)
    {
        var configs = await LoadAgentConfigsAsync(cancellationToken);
        return configs
            .Where(config => !string.IsNullOrWhiteSpace(config.Id))
            .Select(config => config.Id.Trim().ToLowerInvariant())
            .DefaultIfEmpty()
            .Where(id => !string.IsNullOrWhiteSpace(id))
            .ToHashSet(StringComparer.OrdinalIgnoreCase);
    }

    private static string DeriveRole(string agentId) => agentId.ToLowerInvariant() switch
    {
        "iris" => "Orchestrator",
        "product-owner" => "Product Owner",
        "programmer" => "Developer",
        "programmer-fast" => "Developer",
        "reviewer" => "Reviewer",
        "architekt" => "Architect",
        "main" => "Assistant",
        _ => "Custom"
    };

    private static string ResolveModel(AgentConfig config)
        => config.Model?.Primary ?? "deepseek/deepseek-v4-flash";

    private async Task<IReadOnlyList<AgentConfig>> LoadAgentConfigsAsync(CancellationToken cancellationToken)
    {
        var path = configuration.GetValue<string>("AgentConfigPath")
            ?? "/home/node/.openclaw/openclaw.json";

        if (!File.Exists(path))
            return BuildFallbackConfigs();

        var json = await File.ReadAllTextAsync(path, cancellationToken);
        using var document = JsonDocument.Parse(json, new JsonDocumentOptions { AllowTrailingCommas = true });
        var root = document.RootElement;

        if (!root.TryGetProperty("agents", out var agentsElement))
            return BuildFallbackConfigs();

        if (!agentsElement.TryGetProperty("list", out var listElement))
            return BuildFallbackConfigs();

        var defaults = agentsElement.TryGetProperty("defaults", out var defaultsElement)
            ? JsonSerializer.Deserialize<AgentDefaults>(defaultsElement.GetRawText(), JsonOptions)
            : null;

        var configs = new List<AgentConfig>();
        foreach (var agentElement in listElement.EnumerateArray())
        {
            var config = JsonSerializer.Deserialize<AgentConfig>(agentElement.GetRawText(), JsonOptions);
            if (config is null || string.IsNullOrWhiteSpace(config.Id))
                continue;

            // Inherit defaults for missing fields
            if (string.IsNullOrWhiteSpace(config.Name))
                config = config with { Name = config.Id };
            if (string.IsNullOrWhiteSpace(config.Model?.Primary) && defaults?.Model?.Primary is not null)
                config = config with { Model = new AgentModelConfig { Primary = defaults.Model.Primary } };
            if (string.IsNullOrWhiteSpace(config.Workspace) && defaults?.Workspace is not null)
                config = config with { Workspace = defaults.Workspace };

            configs.Add(config);
        }

        return configs.Count > 0 ? configs.AsReadOnly() : BuildFallbackConfigs();
    }

    private static IReadOnlyList<AgentConfig> BuildFallbackConfigs()
        => AgentIdentityCatalog.DefaultConfiguredAgentIds
            .Select(id => new AgentConfig
            {
                Id = id,
                Name = id,
                Model = new AgentModelConfig { Primary = "deepseek/deepseek-v4-flash" }
            })
            .ToList()
            .AsReadOnly();

    private sealed record AgentDefaults
    {
        [JsonPropertyName("workspace")]
        public string? Workspace { get; init; }

        [JsonPropertyName("model")]
        [JsonConverter(typeof(AgentModelConfigConverter))]
        public AgentModelConfig? Model { get; init; }
    }
}