using System.Security.Claims;
using System.Text.Encodings.Web;
using Fitness_core_BE.Helpers;
using Fitness_core_BE.Interfaces;
using Microsoft.AspNetCore.Authentication;
using Microsoft.Extensions.Options;

namespace Fitness_core_BE.Auth
{
    /// <summary>
    /// Constants for the agent API-key authentication scheme / authorization policy.
    /// </summary>
    public static class AgentApiKeyDefaults
    {
        public const string AuthenticationScheme = "AgentApiKey";
        public const string PolicyName = "AgentApiKey";
        public const string HeaderName = "X-Api-Key";

        // Claim types used to carry the resolved agent + client server-side.
        public const string AgentIdClaim = "AgentId";
        public const string ClientIdClaim = "FKClientId";
    }

    public class AgentApiKeyAuthenticationOptions : AuthenticationSchemeOptions { }

    /// <summary>
    /// Authenticates on-prem agents using the high-entropy key sent in the X-Api-Key header.
    /// The key is hashed and matched against an active Agent. On success it exposes the
    /// agent's FKClientId and AgentId via claims + HttpContext.Items so downstream code never
    /// has to trust client/agent identifiers coming from the request body.
    /// </summary>
    public class AgentApiKeyAuthenticationHandler : AuthenticationHandler<AgentApiKeyAuthenticationOptions>
    {
        private readonly IAgentRepo _agentRepo;

        public AgentApiKeyAuthenticationHandler(
            IOptionsMonitor<AgentApiKeyAuthenticationOptions> options,
            ILoggerFactory logger,
            UrlEncoder encoder,
            IAgentRepo agentRepo)
            : base(options, logger, encoder)
        {
            _agentRepo = agentRepo;
        }

        protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
        {
            if (!Request.Headers.TryGetValue(AgentApiKeyDefaults.HeaderName, out var headerValues))
                return AuthenticateResult.NoResult();

            var apiKey = headerValues.FirstOrDefault();
            if (string.IsNullOrWhiteSpace(apiKey))
                return AuthenticateResult.Fail("Missing API key.");

            var hash = ApiKeyHelper.HashApiKey(apiKey);
            var agent = await _agentRepo.GetByApiKeyHashAsync(hash);

            if (agent == null || !agent.IsActive)
                return AuthenticateResult.Fail("Invalid API key.");

            // Expose resolved identity server-side (never trust the body for these).
            Context.Items[AgentApiKeyDefaults.AgentIdClaim] = agent.AgentId.ToString();
            Context.Items[AgentApiKeyDefaults.ClientIdClaim] = agent.FKClientId.ToString();

            var claims = new[]
            {
                new Claim(AgentApiKeyDefaults.AgentIdClaim, agent.AgentId.ToString()),
                new Claim(AgentApiKeyDefaults.ClientIdClaim, agent.FKClientId.ToString()),
                new Claim(ClaimTypes.NameIdentifier, agent.AgentId.ToString())
            };

            var identity = new ClaimsIdentity(claims, Scheme.Name);
            var principal = new ClaimsPrincipal(identity);
            var ticket = new AuthenticationTicket(principal, Scheme.Name);

            return AuthenticateResult.Success(ticket);
        }
    }
}