using Microsoft.AspNetCore.Http.HttpResults;
using Microsoft.AspNetCore.Mvc;
using StellaOps.Auth.Abstractions;
using StellaOps.Policy.Engine.Attestation;

namespace StellaOps.Policy.Engine.Endpoints;

/// <summary>
/// Endpoints for verification policy management per CONTRACT-VERIFICATION-POLICY-006.
/// </summary>
public static class VerificationPolicyEndpoints
{
    public static IEndpointRouteBuilder MapVerificationPolicies(this IEndpointRouteBuilder routes)
    {
        var group = routes.MapGroup("/api/v1/attestor/policies")
            .WithTags("Verification Policies");

        group.MapPost("/", CreatePolicyAsync)
            .WithName("Attestor.CreatePolicy")
            .WithSummary("Create a new verification policy")
            .RequireAuthorization(policy => policy.RequireClaim("scope", StellaOpsScopes.PolicyWrite))
            .Produces<VerificationPolicy>(StatusCodes.Status201Created)
            .Produces<ProblemHttpResult>(StatusCodes.Status400BadRequest)
            .Produces<ProblemHttpResult>(StatusCodes.Status409Conflict);

        group.MapGet("/{policyId}", GetPolicyAsync)
            .WithName("Attestor.GetPolicy")
            .WithSummary("Get a verification policy by ID")
            .RequireAuthorization(policy => policy.RequireClaim("scope", StellaOpsScopes.PolicyRead))
            .Produces<VerificationPolicy>(StatusCodes.Status200OK)
            .Produces<ProblemHttpResult>(StatusCodes.Status404NotFound);

        group.MapGet("/", ListPoliciesAsync)
            .WithName("Attestor.ListPolicies")
            .WithSummary("List verification policies")
            .RequireAuthorization(policy => policy.RequireClaim("scope", StellaOpsScopes.PolicyRead))
            .Produces<VerificationPolicyListResponse>(StatusCodes.Status200OK);

        group.MapPut("/{policyId}", UpdatePolicyAsync)
            .WithName("Attestor.UpdatePolicy")
            .WithSummary("Update a verification policy")
            .RequireAuthorization(policy => policy.RequireClaim("scope", StellaOpsScopes.PolicyWrite))
            .Produces<VerificationPolicy>(StatusCodes.Status200OK)
            .Produces<ProblemHttpResult>(StatusCodes.Status404NotFound);

        group.MapDelete("/{policyId}", DeletePolicyAsync)
            .WithName("Attestor.DeletePolicy")
            .WithSummary("Delete a verification policy")
            .RequireAuthorization(policy => policy.RequireClaim("scope", StellaOpsScopes.PolicyWrite))
            .Produces(StatusCodes.Status204NoContent)
            .Produces<ProblemHttpResult>(StatusCodes.Status404NotFound);

        return routes;
    }

    private static async Task<IResult> CreatePolicyAsync(
        [FromBody] CreateVerificationPolicyRequest request,
        IVerificationPolicyStore store,
        TimeProvider timeProvider,
        CancellationToken cancellationToken)
    {
        if (request == null)
        {
            return Results.BadRequest(CreateProblem(
                "Invalid request",
                "Request body is required.",
                "ERR_ATTEST_001"));
        }

        if (string.IsNullOrWhiteSpace(request.PolicyId))
        {
            return Results.BadRequest(CreateProblem(
                "Invalid request",
                "Policy ID is required.",
                "ERR_ATTEST_002"));
        }

        if (request.PredicateTypes == null || request.PredicateTypes.Count == 0)
        {
            return Results.BadRequest(CreateProblem(
                "Invalid request",
                "At least one predicate type is required.",
                "ERR_ATTEST_003"));
        }

        if (await store.ExistsAsync(request.PolicyId, cancellationToken).ConfigureAwait(false))
        {
            return Results.Conflict(CreateProblem(
                "Policy exists",
                $"Policy '{request.PolicyId}' already exists.",
                "ERR_ATTEST_004"));
        }

        var now = timeProvider.GetUtcNow();
        var policy = new VerificationPolicy(
            PolicyId: request.PolicyId,
            Version: request.Version ?? "1.0.0",
            Description: request.Description,
            TenantScope: request.TenantScope ?? "*",
            PredicateTypes: request.PredicateTypes,
            SignerRequirements: request.SignerRequirements ?? SignerRequirements.Default,
            ValidityWindow: request.ValidityWindow,
            Metadata: request.Metadata,
            CreatedAt: now,
            UpdatedAt: now);

        await store.CreateAsync(policy, cancellationToken).ConfigureAwait(false);

        return Results.Created(
            $"/api/v1/attestor/policies/{policy.PolicyId}",
            policy);
    }

    private static async Task<IResult> GetPolicyAsync(
        [FromRoute] string policyId,
        IVerificationPolicyStore store,
        CancellationToken cancellationToken)
    {
        var policy = await store.GetAsync(policyId, cancellationToken).ConfigureAwait(false);

        if (policy == null)
        {
            return Results.NotFound(CreateProblem(
                "Policy not found",
                $"Policy '{policyId}' was not found.",
                "ERR_ATTEST_005"));
        }

        return Results.Ok(policy);
    }

    private static async Task<IResult> ListPoliciesAsync(
        [FromQuery] string? tenantScope,
        IVerificationPolicyStore store,
        CancellationToken cancellationToken)
    {
        var policies = await store.ListAsync(tenantScope, cancellationToken).ConfigureAwait(false);

        return Results.Ok(new VerificationPolicyListResponse(
            Policies: policies,
            Total: policies.Count));
    }

    private static async Task<IResult> UpdatePolicyAsync(
        [FromRoute] string policyId,
        [FromBody] UpdateVerificationPolicyRequest request,
        IVerificationPolicyStore store,
        TimeProvider timeProvider,
        CancellationToken cancellationToken)
    {
        if (request == null)
        {
            return Results.BadRequest(CreateProblem(
                "Invalid request",
                "Request body is required.",
                "ERR_ATTEST_001"));
        }

        var now = timeProvider.GetUtcNow();

        var updated = await store.UpdateAsync(
            policyId,
            existing => existing with
            {
                Version = request.Version ?? existing.Version,
                Description = request.Description ?? existing.Description,
                PredicateTypes = request.PredicateTypes ?? existing.PredicateTypes,
                SignerRequirements = request.SignerRequirements ?? existing.SignerRequirements,
                ValidityWindow = request.ValidityWindow ?? existing.ValidityWindow,
                Metadata = request.Metadata ?? existing.Metadata,
                UpdatedAt = now
            },
            cancellationToken).ConfigureAwait(false);

        if (updated == null)
        {
            return Results.NotFound(CreateProblem(
                "Policy not found",
                $"Policy '{policyId}' was not found.",
                "ERR_ATTEST_005"));
        }

        return Results.Ok(updated);
    }

    private static async Task<IResult> DeletePolicyAsync(
        [FromRoute] string policyId,
        IVerificationPolicyStore store,
        CancellationToken cancellationToken)
    {
        var deleted = await store.DeleteAsync(policyId, cancellationToken).ConfigureAwait(false);

        if (!deleted)
        {
            return Results.NotFound(CreateProblem(
                "Policy not found",
                $"Policy '{policyId}' was not found.",
                "ERR_ATTEST_005"));
        }

        return Results.NoContent();
    }

    private static ProblemDetails CreateProblem(string title, string detail, string? errorCode = null)
    {
        var problem = new ProblemDetails
        {
            Title = title,
            Detail = detail,
            Status = StatusCodes.Status400BadRequest
        };

        if (!string.IsNullOrWhiteSpace(errorCode))
        {
            problem.Extensions["error_code"] = errorCode;
        }

        return problem;
    }
}

/// <summary>
/// Response for listing verification policies.
/// </summary>
public sealed record VerificationPolicyListResponse(
    [property: System.Text.Json.Serialization.JsonPropertyName("policies")] IReadOnlyList<VerificationPolicy> Policies,
    [property: System.Text.Json.Serialization.JsonPropertyName("total")] int Total);