namespace marlin.web.Services;

using System.Security.Claims;
using System.Text.Encodings.Web;
using Data;
using Microsoft.AspNetCore.Authentication;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;
using Microsoft.Extensions.Primitives;

public class AgentSchemeOptions : AuthenticationSchemeOptions
{
    public const string Name = "Agent";
    public string AgentHeader { get; set; } = "Agent";
    public string JobHeader { get; set; } = "Job";
}

public class AgentAuthenticationHandler : AuthenticationHandler<AgentSchemeOptions>
{
    private readonly ApplicationDbContext _dbContext;

    public AgentAuthenticationHandler(
        IOptionsMonitor<AgentSchemeOptions> options,
        ILoggerFactory logger,
        UrlEncoder encoder,
        ApplicationDbContext dbContext) : base(options, logger, encoder)
    {
        this._dbContext = dbContext;
    }

    private bool TryReadPair(string headerName, out Guid id, out string token)
    {
        id = Guid.Empty;
        token = string.Empty;

        if (!Request.Headers.TryGetValue(headerName, out StringValues header))
            return false;

        var parts = header.ToString().Split(' ', 2);
        if (parts.Length != 2 || parts[1].Length == 0)
            return false;

        token = parts[1];
        return Guid.TryParse(parts[0], out id);
    }

    protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
    {
        var claims = new List<Claim>();
        
        if (!TryReadPair(Options.AgentHeader, out var agentId, out var agentToken))
            return AuthenticateResult.NoResult();

        var agent = await this._dbContext.Agents
            .FirstOrDefaultAsync(x => x.Id == agentId && x.AuthToken == agentToken);

        if (agent == null)
            return AuthenticateResult.Fail("Invalid agent credentials.");
        
        claims.Add(new Claim("agent_id", agent.Id.ToString()));

        if (TryReadPair(Options.JobHeader, out var jobId, out var jobToken))
        {
            var job = await this._dbContext.Jobs
                .FirstOrDefaultAsync(x => x.Id == jobId && x.AgentId == agent.Id && x.ClaimToken == jobToken);

            if (job == null)
                return AuthenticateResult.Fail("Invalid job claim token.");

            claims.Add(new Claim("job_id", job.Id.ToString()));
        }

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

        return AuthenticateResult.Success(ticket);
    }
}