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? seed = null, string? genesis = null, string role = "agent")
    {
        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();
        }

        // 固定了操作员的创世（--genesis）和码的种子（--seed）：先取信任链，确认这个面板的操作员集合和委托确实是固定的创世签出来的，
        // 再用码的私钥签绑定。任何一步对不上都不注册，也不把自己的密钥交出去。
        Binding? binding = null;
        string? bindingStatement = null;
        string? bindingSignature = null;
        TrustBundle? bundle = null;
        if (seed is not null || genesis is not null)
        {
            Result<(TrustBundle Bundle, Binding Binding, string Statement, string Signature)> trusted =
                await EstablishTrustAsync(http, server, joinToken, name, role, seed, genesis, identity.PublicKeySpki, tlsPublicKey, time, ct);
            if (!trusted.TryGet(out (TrustBundle Bundle, Binding Binding, string Statement, string Signature) value, out FleetError? trustError))
            {
                return Result<EnrollmentResult>.Fail(trustError);
            }

            bundle = value.Bundle;
            binding = value.Binding;
            bindingStatement = value.Statement;
            bindingSignature = value.Signature;
        }

        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,
            ["binding"] = bindingStatement,
            ["binding_signature"] = bindingSignature,
        };

        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 && binding is not null)
        {
            TrustAnchor.Pin(identityDirectory, genesis!, bundle.Chain, new MemberProofDto { Grant = bundle.Grant!, Binding = bindingStatement!, BindingSignature = bindingSignature! });
        }

        // 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 Bundle, Binding Binding, string Statement, string Signature)>> EstablishTrustAsync(
        HttpClient http, Uri server, string joinToken, string name, string role, string? seedText, string? genesis, byte[] nodeKey, byte[] peerKey, TimeProvider time, CancellationToken ct)
    {
        static Result<(TrustBundle, Binding, string, string)> Refuse(string reason) => Result<(TrustBundle, Binding, string, string)>.Fail(FleetErrors.ProofInvalid, "refusing to enroll: " + reason);

        if (seedText is null || genesis is null)
        {
            return Refuse("--seed and --genesis go together (the panel's install command has both)");
        }

        if (!Base64Url.TryDecode(seedText, out byte[] seed) || seed.Length != 32)
        {
            return Refuse("the code seed is malformed");
        }

        if (OperatorTrust.AuthToken(seed) != joinToken)
        {
            return Refuse("the join token is not derived from the code seed");
        }

        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, Binding, string, string)>.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?.Grant is null || bundle.Chain.Count == 0)
        {
            return Refuse("the panel has no operator trust set up, or this code carries no grant from the operator");
        }

        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)");
        }

        Grant? grant = OperatorTrust.ParseGrant(bundle.Grant.Statement);
        long now = time.GetUtcNow().ToUnixTimeMilliseconds();
        if (grant is null || !OperatorTrust.VerifyOperator(bundle.Grant.ToSigned(), current))
        {
            return Refuse("the grant is not signed by your operator passkey");
        }

        if (grant.AuthHash != OperatorTrust.AuthHash(joinToken) || grant.Role != role || now < grant.NotBeforeMs || now > grant.NotAfterMs)
        {
            return Refuse("the grant is not for this code, this role, or this time");
        }

        using ECDsa? codeKey = OperatorTrust.CodeSigningKey(seed, grant.CodeKey);
        if (codeKey is null)
        {
            return Refuse("the code seed does not match the grant's code key");
        }

        var binding = new Binding(name, role, nodeKey, peerKey, grant.AuthHash, now);
        string signature = OperatorTrust.SignBinding(codeKey, binding, out string statement);
        return Result<(TrustBundle, Binding, string, string)>.Ok((bundle, binding, statement, signature));
    }
}