package server

import (
	"crypto/ecdsa"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"time"

	"gitea.songhuwan.com/actions/docker-compose-updater/internal/auth"
	"gitea.songhuwan.com/actions/docker-compose-updater/internal/docker"
)

// Handler 持有 HTTP handler 的依赖。
type Handler struct {
	verifyKey   *ecdsa.PublicKey
	sessionMgr *auth.SessionManager
	nonceCache *auth.NonceCache
	docker     *docker.Updater
	timeWindow time.Duration
}

// NewHandler 创建 Handler。
func NewHandler(
	verifyKey *ecdsa.PublicKey,
	sessionMgr *auth.SessionManager,
	nonceCache *auth.NonceCache,
	docker *docker.Updater,
	timeWindow time.Duration,
) *Handler {
	return &Handler{
		verifyKey:   verifyKey,
		sessionMgr: sessionMgr,
		nonceCache:  nonceCache,
		docker:      docker,
		timeWindow:  timeWindow,
	}
}

// --- 请求/响应结构 ---

// phase1Req 第一阶段请求。
type phase1Req struct {
	V     int    `json:"v"`
	TS    int64  `json:"ts"`
	Nonce string `json:"nonce"`
	Sig   string `json:"sig"`
}

// phase2Req 第二阶段请求。
type phase2Req struct {
	V     int    `json:"v"`
	TS    int64  `json:"ts"`
	Nonce string `json:"nonce"`
	KeyID string `json:"key_id"`
	Data  string `json:"data"` // AES-GCM 密文 base64
}

// plainPayload 解密后的明文请求。
type plainPayload struct {
	Project string `json:"project"`
	Service string `json:"service"`
	Action  string `json:"action"` // update / pull / restart
}

// --- 处理函数 ---

// HandleSession Phase 1: 验证签名 → 生成会话密钥 → 返回。
func (h *Handler) HandleSession(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeError(w, http.StatusMethodNotAllowed, "only POST allowed")
		return
	}

	var req phase1Req
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json")
		return
	}
	if req.V != 1 {
		writeError(w, http.StatusBadRequest, "unsupported protocol version")
		return
	}
	if req.Sig == "" {
		writeError(w, http.StatusBadRequest, "missing sig")
		return
	}
	if err := h.checkTimestamp(req.TS); err != nil {
		writeError(w, http.StatusUnauthorized, err.Error())
		return
	}
	if !h.nonceCache.Check(req.Nonce) {
		writeError(w, http.StatusUnauthorized, "nonce reused")
		return
	}

	// 验证 ECDSA 签名：sign("v.ts.nonce")
	signData := fmt.Sprintf("%d.%d.%s", req.V, req.TS, req.Nonce)
	if !auth.Verify(h.verifyKey, []byte(signData), req.Sig) {
		writeError(w, http.StatusUnauthorized, "signature verification failed")
		return
	}

	// 生成会话密钥，用 nonce 作为 key_id
	key := make([]byte, 32)
	// 使用随机数作为会话密钥
	keyBytes, err := h.sessionMgr.GenerateKey(req.Nonce)
	if err != nil {
		slog.Error("generate session key", "error", err)
		writeError(w, http.StatusInternalServerError, "internal error")
		return
	}
	_ = key

	writeJSON(w, http.StatusOK, map[string]any{
		"key":        base64.StdEncoding.EncodeToString(keyBytes),
		"key_id":     req.Nonce,
		"expires_in": 30,
	})
}

// HandleHook Phase 2: 解密 payload → 执行 Docker 操作。
func (h *Handler) HandleHook(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		writeError(w, http.StatusMethodNotAllowed, "only POST allowed")
		return
	}

	var req phase2Req
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json")
		return
	}
	if req.V != 1 {
		writeError(w, http.StatusBadRequest, "unsupported protocol version")
		return
	}
	if err := h.checkTimestamp(req.TS); err != nil {
		writeError(w, http.StatusUnauthorized, err.Error())
		return
	}
	if !h.nonceCache.Check(req.Nonce) {
		writeError(w, http.StatusUnauthorized, "nonce reused")
		return
	}

	// 获取会话密钥
	sessionKey := h.sessionMgr.GetKey(req.KeyID)
	if sessionKey == nil {
		writeError(w, http.StatusUnauthorized, "invalid or expired session key")
		return
	}

	// 解密 payload
	ciphertext, err := base64.StdEncoding.DecodeString(req.Data)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid data encoding")
		return
	}
	plaintext, err := auth.Decrypt(ciphertext, sessionKey)
	if err != nil {
		writeError(w, http.StatusUnauthorized, "decrypt failed")
		return
	}

	var payload plainPayload
	if err := json.Unmarshal(plaintext, &payload); err != nil {
		writeError(w, http.StatusBadRequest, "invalid payload json")
		return
	}
	if payload.Project == "" || payload.Service == "" || payload.Action == "" {
		writeError(w, http.StatusBadRequest, "project, service, action required")
		return
	}

	slog.Info("hook",
		"project", payload.Project,
		"service", payload.Service,
		"action", payload.Action,
	)

	var result string
	switch payload.Action {
	case "pull":
		info, err := h.docker.FindContainerByLabels(payload.Project, payload.Service)
		if err != nil {
			writeError(w, http.StatusNotFound, err.Error())
			return
		}
		if err := h.docker.PullImage(info.Image); err != nil {
			writeError(w, http.StatusInternalServerError, "pull: "+err.Error())
			return
		}
		result = "image pulled"

	case "update":
		id, err := h.docker.RecreateContainer(payload.Project, payload.Service)
		if err != nil {
			writeError(w, http.StatusInternalServerError, "update: "+err.Error())
			return
		}
		result = fmt.Sprintf("container recreated: %s", id[:12])

	case "restart":
		id, err := h.docker.RestartContainer(payload.Project, payload.Service)
		if err != nil {
			writeError(w, http.StatusInternalServerError, "restart: "+err.Error())
			return
		}
		result = fmt.Sprintf("container restarted: %s", id[:12])

	default:
		writeError(w, http.StatusBadRequest, "unknown action: "+payload.Action)
		return
	}

	writeJSON(w, http.StatusOK, map[string]string{
		"status":  "ok",
		"project": payload.Project,
		"service": payload.Service,
		"action":  payload.Action,
		"message": result,
	})
}

// Health 健康检查。
func (h *Handler) Health(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

// --- 工具函数 ---

func (h *Handler) checkTimestamp(ts int64) error {
	now := time.Now().Unix()
	diff := now - ts
	if diff < 0 {
		diff = -diff
	}
	if diff > int64(h.timeWindow.Seconds()) {
		return fmt.Errorf("timestamp outside window")
	}
	return nil
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(v)
}

func writeError(w http.ResponseWriter, status int, msg string) {
	writeJSON(w, status, map[string]string{"error": msg})
}