using System.Collections.Generic;
using Swashbuckle.AspNetCore.SwaggerGen;
using System.Globalization;
using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.OpenApi;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.OpenApi.Models;
using StellaOps.VulnExplorer.Api.Data;
using StellaOps.VulnExplorer.Api.Models;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen(options =>
{
    options.SwaggerDoc("v1", new OpenApiInfo
    {
        Title = "StellaOps Vuln Explorer API",
        Version = "v1",
        Description = "Deterministic vulnerability listing/detail and VEX decision endpoints"
    });
});

// Configure JSON serialization with enum string converter
builder.Services.ConfigureHttpJsonOptions(options =>
{
    options.SerializerOptions.Converters.Add(new JsonStringEnumConverter());
    options.SerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
});

// Register VEX decision store
builder.Services.AddSingleton<VexDecisionStore>();

var app = builder.Build();

app.UseSwagger();
app.UseSwaggerUI();

app.UseHttpsRedirection();

app.MapGet("/v1/vulns", ([AsParameters] VulnFilter filter) =>
{
    if (string.IsNullOrWhiteSpace(filter.Tenant))
    {
        return Results.BadRequest(new { error = "x-stella-tenant required" });
    }

    var data = ApplyFilter(SampleData.Summaries, filter);
    var pageSize = Math.Clamp(filter.PageSize ?? 50, 1, 200);
    var offset = ParsePageToken(filter.PageToken);

    var page = data.Skip(offset).Take(pageSize).ToArray();
    var nextOffset = offset + page.Length;
    var next = nextOffset < data.Count ? nextOffset.ToString(CultureInfo.InvariantCulture) : null;

    var response = new VulnListResponse(page, next);
    return Results.Ok(response);
})
.WithOpenApi();

app.MapGet("/v1/vulns/{id}", ([FromHeader(Name = "x-stella-tenant")] string? tenant, string id) =>
{
    if (string.IsNullOrWhiteSpace(tenant))
    {
        return Results.BadRequest(new { error = "x-stella-tenant required" });
    }

    return SampleData.TryGetDetail(id, out var detail) && detail is not null
        ? Results.Ok(detail)
        : Results.NotFound();
})
.WithOpenApi();

// ============================================================================
// VEX Decision Endpoints (API-VEX-06-001, API-VEX-06-002, API-VEX-06-003)
// ============================================================================

app.MapPost("/v1/vex-decisions", (
    [FromHeader(Name = "x-stella-tenant")] string? tenant,
    [FromHeader(Name = "x-stella-user-id")] string? userId,
    [FromHeader(Name = "x-stella-user-name")] string? userName,
    [FromBody] CreateVexDecisionRequest request,
    VexDecisionStore store) =>
{
    if (string.IsNullOrWhiteSpace(tenant))
    {
        return Results.BadRequest(new { error = "x-stella-tenant required" });
    }

    if (string.IsNullOrWhiteSpace(request.VulnerabilityId))
    {
        return Results.BadRequest(new { error = "vulnerabilityId is required" });
    }

    if (request.Subject is null)
    {
        return Results.BadRequest(new { error = "subject is required" });
    }

    var effectiveUserId = userId ?? "anonymous";
    var effectiveUserName = userName ?? "Anonymous User";

    var decision = store.Create(request, effectiveUserId, effectiveUserName);
    return Results.Created($"/v1/vex-decisions/{decision.Id}", decision);
})
.WithName("CreateVexDecision")
.WithOpenApi();

app.MapPatch("/v1/vex-decisions/{id:guid}", (
    [FromHeader(Name = "x-stella-tenant")] string? tenant,
    Guid id,
    [FromBody] UpdateVexDecisionRequest request,
    VexDecisionStore store) =>
{
    if (string.IsNullOrWhiteSpace(tenant))
    {
        return Results.BadRequest(new { error = "x-stella-tenant required" });
    }

    var updated = store.Update(id, request);
    return updated is not null
        ? Results.Ok(updated)
        : Results.NotFound(new { error = $"VEX decision {id} not found" });
})
.WithName("UpdateVexDecision")
.WithOpenApi();

app.MapGet("/v1/vex-decisions", ([AsParameters] VexDecisionFilter filter, VexDecisionStore store) =>
{
    if (string.IsNullOrWhiteSpace(filter.Tenant))
    {
        return Results.BadRequest(new { error = "x-stella-tenant required" });
    }

    var pageSize = Math.Clamp(filter.PageSize ?? 50, 1, 200);
    var offset = ParsePageToken(filter.PageToken);

    var decisions = store.Query(
        vulnerabilityId: filter.VulnerabilityId,
        subjectName: filter.Subject,
        status: filter.Status,
        skip: offset,
        take: pageSize);

    var nextOffset = offset + decisions.Count;
    var next = nextOffset < store.Count() ? nextOffset.ToString(CultureInfo.InvariantCulture) : null;

    return Results.Ok(new VexDecisionListResponse(decisions, next));
})
.WithName("ListVexDecisions")
.WithOpenApi();

app.MapGet("/v1/vex-decisions/{id:guid}", (
    [FromHeader(Name = "x-stella-tenant")] string? tenant,
    Guid id,
    VexDecisionStore store) =>
{
    if (string.IsNullOrWhiteSpace(tenant))
    {
        return Results.BadRequest(new { error = "x-stella-tenant required" });
    }

    var decision = store.Get(id);
    return decision is not null
        ? Results.Ok(decision)
        : Results.NotFound(new { error = $"VEX decision {id} not found" });
})
.WithName("GetVexDecision")
.WithOpenApi();

app.Run();

static int ParsePageToken(string? token) =>
    int.TryParse(token, out var offset) && offset >= 0 ? offset : 0;

static IReadOnlyList<VulnSummary> ApplyFilter(IReadOnlyList<VulnSummary> source, VulnFilter filter)
{
    IEnumerable<VulnSummary> query = source;

    if (filter.Cve is { Length: > 0 })
    {
        var set = filter.Cve.ToHashSet(StringComparer.OrdinalIgnoreCase);
        query = query.Where(v => v.CveIds.Any(set.Contains));
    }

    if (filter.Purl is { Length: > 0 })
    {
        var set = filter.Purl.ToHashSet(StringComparer.OrdinalIgnoreCase);
        query = query.Where(v => v.Purls.Any(set.Contains));
    }

    if (filter.Severity is { Length: > 0 })
    {
        var set = filter.Severity.ToHashSet(StringComparer.OrdinalIgnoreCase);
        query = query.Where(v => set.Contains(v.Severity));
    }

    if (filter.Exploitability is not null)
    {
        query = query.Where(v => string.Equals(v.Exploitability, filter.Exploitability, StringComparison.OrdinalIgnoreCase));
    }

    if (filter.FixAvailable is not null)
    {
        query = query.Where(v => v.FixAvailable == filter.FixAvailable);
    }

    // deterministic ordering: score desc, id asc
    query = query
        .OrderByDescending(v => v.Score)
        .ThenBy(v => v.Id, StringComparer.Ordinal);

    return query.ToArray();
}

public record VulnFilter(
    [FromHeader(Name = "x-stella-tenant")] string? Tenant,
    [FromQuery(Name = "policyVersion")] string? PolicyVersion,
    [FromQuery(Name = "pageSize")] int? PageSize,
    [FromQuery(Name = "pageToken")] string? PageToken,
    [FromQuery(Name = "cve")] string[]? Cve,
    [FromQuery(Name = "purl")] string[]? Purl,
    [FromQuery(Name = "severity")] string[]? Severity,
    [FromQuery(Name = "exploitability")] string? Exploitability,
    [FromQuery(Name = "fixAvailable")] bool? FixAvailable);

public record VexDecisionFilter(
    [FromHeader(Name = "x-stella-tenant")] string? Tenant,
    [FromQuery(Name = "vulnerabilityId")] string? VulnerabilityId,
    [FromQuery(Name = "subject")] string? Subject,
    [FromQuery(Name = "status")] VexStatus? Status,
    [FromQuery(Name = "pageSize")] int? PageSize,
    [FromQuery(Name = "pageToken")] string? PageToken);

public partial class Program { }