using System.Security.Cryptography;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;
using System.Text.Json.Serialization;
using Fleet.Core;
using Fleet.Hosting;
using Fleet.Identity;

namespace Fleet.Enrollment.Client;

[JsonSerializable(typeof(TrustBundle))]
internal sealed partial class TrustBundleContext : JsonSerializerContext;

public sealed record EnrollmentResult(string NodeId, string Status, string IdentityDirectory, bool Pinned = false);

/// <summary>
/// 用加入令牌注册（供 <c>fleet-enroll</c> 使用，也可以嵌入产品自己的安装工具）：
/// 生成身份密钥和 TLS 证书 → 用身份私钥签名持有证明 → 调用注册端点 → 写入身份目录。
/// 注册逻辑只存在于这里，常驻的业务进程不包含注册代码，也不使用 HttpClient。
/// </summary>
public static class EnrollmentClient
{
    public static async Task<Result<EnrollmentResult>> EnrollAsync(
        HttpClient http, Uri server, string joinToken, string name, string identityDirectory, string nodeVersion, JsonNode? productMeta, TimeProvider time, CancellationToken ct,
        string? genesis = null, IReadOnlyList<string>? controllers = null)
    {
        string nodeFile = Path.Combine(identityDirectory, LoadedNodeIdentity.NodeFileName);
        if (File.Exists(nodeFile))
        {
            return Result<EnrollmentResult>.Fail(FleetErrors.NameConflict, $"{nodeFile} already exists: this node is already enrolled (remove the directory to enroll again)");
        }

        using NodeIdentity identity = NodeIdentity.Generate();
        byte[] pfx = NodeCertificate.CreateSelfSignedPfx(name, TimeSpan.FromDays(3650), time);
        byte[] spki;
        byte[] tlsPublicKey;
        using (var certificate = NodeCertificate.LoadPfx(pfx))
        {
            spki = NodeCertificate.SpkiFingerprint(certificate);
            tlsPublicKey = certificate.PublicKey.ExportSubjectPublicKeyInfo();
        }

        // 安装命令里带了创世指纹（--genesis）和属主（--controllers）：先取操作员集合链，从固定的创世验起，
        // 属主必须是集合里的凭证；对不上就不注册，也不把自己的密钥交出去。通过之后固定到本地 trust.json，Backend 之后改不了。
        TrustBundle? bundle = null;
        if (genesis is not null)
        {
            if (controllers is not { Count: > 0 })
            {
                // 每个节点都必须有属主：没有属主的节点没有人能授权它的敏感操作
                return Result<EnrollmentResult>.Fail(FleetErrors.InvalidParams, "an owner is required: pass the passkey credential ids from the panel's command (--controllers)");
            }

            Result<TrustBundle> trusted = await FetchTrustAsync(http, server, joinToken, genesis, controllers ?? [], ct);
            if (!trusted.TryGet(out bundle, out FleetError? trustError))
            {
                return Result<EnrollmentResult>.Fail(trustError);
            }
        }

        string pubkey = Convert.ToBase64String(identity.PublicKeySpki);
        string tokenHash = Convert.ToHexStringLower(SHA256.HashData(Encoding.UTF8.GetBytes(joinToken)));
        var body = new JsonObject
        {
            ["join_token"] = joinToken,
            ["name"] = name,
            ["pubkey"] = pubkey,
            ["tls_spki"] = Convert.ToBase64String(spki),
            ["tls_pubkey"] = Convert.ToBase64String(tlsPublicKey),
            ["proof"] = Convert.ToBase64String(identity.Sign(SignaturePurpose.Enroll, tokenHash, pubkey)),
            ["node_version"] = nodeVersion,
            ["meta"] = productMeta,
        };

        using var content = new StringContent(body.ToJsonString(), Encoding.UTF8, "application/json");
        using HttpResponseMessage response = await http.PostAsync(new Uri(server, "/api/agent/v1/enroll"), content, ct);
        string text = await response.Content.ReadAsStringAsync(ct);
        if (!response.IsSuccessStatusCode)
        {
            string code = "fleet_internal";
            string detail = text;
            try
            {
                JsonNode? problem = JsonNode.Parse(text);
                code = problem?["code"]?.GetValue<string>() ?? code;
                detail = problem?["detail"]?.GetValue<string>() ?? detail;
            }
            catch (JsonException)
            {
                // 不是 problem+json：原样返回
            }

            return Result<EnrollmentResult>.Fail(new ErrorCode(code), $"{(int)response.StatusCode}: {detail}");
        }

        JsonNode result = JsonNode.Parse(text)!;
        string nodeId = result["node_id"]!.GetValue<string>();
        var store = new ConfigStore(identityDirectory);
        store.Write(LoadedNodeIdentity.KeyFileName, identity.ExportPkcs8());
        store.Write(LoadedNodeIdentity.TlsFileName, pfx);
        if (bundle is not null)
        {
            TrustAnchor.Pin(identityDirectory, genesis!, bundle.Chain, controllers ?? []);
        }

        // node.json 最后写：它存在就表示注册完整完成
        store.Write(
            LoadedNodeIdentity.NodeFileName,
            JsonSerializer.SerializeToUtf8Bytes(new NodeFile { NodeId = nodeId, Server = server.ToString().TrimEnd('/'), TlsSpki = Convert.ToBase64String(spki) }, NodeFileContext.Default.NodeFile));
        return Result<EnrollmentResult>.Ok(new EnrollmentResult(nodeId, result["status"]!.GetValue<string>(), identityDirectory, bundle is not null));
    }

    private static async Task<Result<TrustBundle>> FetchTrustAsync(HttpClient http, Uri server, string joinToken, string genesis, IReadOnlyList<string> controllers, CancellationToken ct)
    {
        static Result<TrustBundle> Refuse(string reason) => Result<TrustBundle>.Fail(FleetErrors.ProofInvalid, "refusing to enroll: " + reason);

        using var request = new StringContent(new JsonObject { ["join_token"] = joinToken }.ToJsonString(), Encoding.UTF8, "application/json");
        using HttpResponseMessage response = await http.PostAsync(new Uri(server, "/api/agent/v1/enroll/trust"), request, ct);
        if (!response.IsSuccessStatusCode)
        {
            return Result<TrustBundle>.Fail(FleetErrors.JoinTokenInvalid, $"{(int)response.StatusCode}: the panel would not give the trust chain");
        }

        TrustBundle? bundle = JsonSerializer.Deserialize(await response.Content.ReadAsStringAsync(ct), TrustBundleContext.Default.TrustBundle);
        if (bundle is null || bundle.Chain.Count == 0)
        {
            return Refuse("the panel has no operator trust root set up");
        }

        OperatorSet? current = OperatorTrust.VerifyChain(genesis, [.. bundle.Chain.Select(c => c.ToSigned())]);
        if (current is null)
        {
            return Refuse("the panel's operator set does not match the pinned genesis fingerprint (wrong panel, or the panel was tampered with)");
        }

        if (controllers.Any(c => current.Keys.All(k => k.CredentialId != c)))
        {
            return Refuse("an owner passkey in the install command is not in the operator set");
        }

        return Result<TrustBundle>.Ok(bundle);
    }
}