// Package iot 实现设备命令、Outbox 认领和上行报文持久化。
package iot

import (
	"crypto/subtle"
	"encoding/json"
	"errors"
	"net/http"
	"strings"
	"time"

	"git.apinb.com/heqiapp/platforms/backend/api/internal/config"
	"git.apinb.com/heqiapp/platforms/backend/api/internal/impl"
	"git.apinb.com/heqiapp/platforms/backend/api/internal/models"
	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

type commandRequest struct {
	DeviceIdentity string    `json:"device_identity"`
	DeviceID       string    `json:"device_id"`
	IdempotencyKey string    `json:"idempotency_key"`
	Action         string    `json:"action"`
	ExpiresAt      time.Time `json:"expires_at"`
	KeyID          byte      `json:"key_id"`
	DeviceKind     byte      `json:"device_kind"`
	DeviceType     byte      `json:"device_type"`
	DeviceModel    [3]byte   `json:"device_model"`
	Controller     byte      `json:"controller"`
	Loop           byte      `json:"loop"`
	Component      byte      `json:"component"`
}

func RequireInternalToken() gin.HandlerFunc {
	return func(ctx *gin.Context) {
		actual := ctx.GetHeader("X-Heqi-Iot-Token")
		expected := config.Spec.IoT.InternalServiceToken
		if len(actual) != len(expected) || subtle.ConstantTimeCompare([]byte(actual), []byte(expected)) != 1 {
			ctx.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"code": "IOT_UNAUTHORIZED"})
			return
		}
		ctx.Next()
	}
}

func CreateCommand(ctx *gin.Context) {
	var request commandRequest
	if err := ctx.ShouldBindJSON(&request); err != nil || request.DeviceIdentity == "" || len(request.DeviceID) != 16 || request.IdempotencyKey == "" || (request.Action != "open_valve" && request.Action != "close_valve") {
		ctx.JSON(422, gin.H{"code": "IOT_COMMAND_INVALID"})
		return
	}
	if request.ExpiresAt.IsZero() {
		request.ExpiresAt = time.Now().Add(30 * time.Second)
	}
	var existing models.IotCommand
	if err := impl.DBService.Where("idempotency_key = ?", request.IdempotencyKey).First(&existing).Error; err == nil {
		ctx.JSON(200, existing)
		return
	} else if err != gorm.ErrRecordNotFound {
		ctx.JSON(500, gin.H{"code": "IOT_COMMAND_QUERY_FAILED"})
		return
	}
	payload, _ := json.Marshal(request)
	command := models.IotCommand{Entity: models.Entity{Identity: models.NewIdentity()}, DeviceIdentity: request.DeviceIdentity, DeviceID: request.DeviceID, IdempotencyKey: request.IdempotencyKey, Action: request.Action, RequestPayload: string(payload), CommandStatus: "accepted", ExpiresAt: request.ExpiresAt}
	outbox := models.IotOutbox{Identity: models.NewIdentity(), CommandIdentity: command.Identity, EventType: "iot.command.accepted", Payload: string(payload), OutboxStatus: "pending", AvailableAt: time.Now()}
	err := impl.DBService.Transaction(func(tx *gorm.DB) error {
		if err := tx.Create(&command).Error; err != nil {
			return err
		}
		return tx.Create(&outbox).Error
	})
	if err != nil {
		ctx.JSON(500, gin.H{"code": "IOT_COMMAND_CREATE_FAILED"})
		return
	}
	ctx.JSON(http.StatusAccepted, command)
}

func GetCommand(ctx *gin.Context) {
	var command models.IotCommand
	if err := impl.DBService.Where("identity = ?", ctx.Param("identity")).First(&command).Error; err != nil {
		ctx.JSON(404, gin.H{"code": "IOT_COMMAND_NOT_FOUND"})
		return
	}
	ctx.JSON(200, command)
}

func ClaimOutbox(ctx *gin.Context) {
	var outbox models.IotOutbox
	err := impl.DBService.Transaction(func(tx *gorm.DB) error {
		now := time.Now()
		err := tx.Clauses(clause.Locking{Strength: "UPDATE", Options: "SKIP LOCKED"}).Where("(outbox_status IN ? AND available_at <= ?) OR (outbox_status = ? AND updated_at < ?)", []string{"pending", "retry"}, now, "processing", now.Add(-time.Minute)).Order("id").First(&outbox).Error
		if err != nil {
			return err
		}
		return tx.Model(&outbox).Updates(map[string]any{"outbox_status": "processing", "attempts": gorm.Expr("attempts + 1"), "updated_at": time.Now()}).Error
	})
	if err == gorm.ErrRecordNotFound {
		ctx.Status(http.StatusNoContent)
		return
	}
	if err != nil {
		ctx.JSON(500, gin.H{"code": "IOT_OUTBOX_CLAIM_FAILED"})
		return
	}
	ctx.JSON(200, outbox)
}

func CompleteOutbox(ctx *gin.Context) {
	var request struct {
		Success      bool   `json:"success"`
		PacketNumber uint16 `json:"packet_number"`
		ErrorCode    string `json:"error_code"`
	}
	if ctx.ShouldBindJSON(&request) != nil {
		ctx.JSON(400, gin.H{"code": "IOT_OUTBOX_RESULT_INVALID"})
		return
	}
	var outbox models.IotOutbox
	if err := impl.DBService.Where("identity = ?", ctx.Param("identity")).First(&outbox).Error; err != nil {
		ctx.JSON(404, gin.H{"code": "IOT_OUTBOX_NOT_FOUND"})
		return
	}
	now := time.Now()
	err := impl.DBService.Transaction(func(tx *gorm.DB) error {
		if request.Success {
			if err := tx.Model(&outbox).Updates(map[string]any{"outbox_status": "published", "updated_at": now}).Error; err != nil {
				return err
			}
			return tx.Model(&models.IotCommand{}).Where("identity = ?", outbox.CommandIdentity).Updates(map[string]any{"command_status": "pending_confirmation", "packet_number": request.PacketNumber, "dispatched_at": now, "updated_at": now}).Error
		}
		delay := time.Duration(outbox.Attempts+1) * time.Second
		if delay > time.Minute {
			delay = time.Minute
		}
		if err := tx.Model(&outbox).Updates(map[string]any{"outbox_status": "retry", "available_at": now.Add(delay), "updated_at": now}).Error; err != nil {
			return err
		}
		return tx.Model(&models.IotCommand{}).Where("identity = ?", outbox.CommandIdentity).Updates(map[string]any{"command_status": "dispatch_failed", "error_code": request.ErrorCode, "updated_at": now}).Error
	})
	if err != nil {
		ctx.JSON(500, gin.H{"code": "IOT_OUTBOX_RESULT_FAILED"})
		return
	}
	ctx.Status(204)
}

func SaveDeviceMessage(ctx *gin.Context) {
	data, err := ctx.GetRawData()
	if err != nil || len(data) == 0 {
		ctx.JSON(400, gin.H{"code": "IOT_MESSAGE_INVALID"})
		return
	}
	var envelope struct {
		Type, Topic, DeviceID, ReceivedAt, PayloadHex string
		Frame                                         json.RawMessage `json:"frame"`
	}
	if json.Unmarshal(data, &envelope) != nil || envelope.ReceivedAt == "" {
		ctx.JSON(422, gin.H{"code": "IOT_MESSAGE_INVALID"})
		return
	}
	received, err := time.Parse(time.RFC3339Nano, envelope.ReceivedAt)
	if err != nil {
		ctx.JSON(422, gin.H{"code": "IOT_RECEIVED_AT_INVALID"})
		return
	}
	message := models.IotDeviceMessage{Identity: models.NewIdentity(), DeviceID: envelope.DeviceID, Topic: envelope.Topic, MessageType: envelope.Type, PayloadHex: strings.ToLower(envelope.PayloadHex), DecodedFrame: string(envelope.Frame), ReceivedAt: received}
	var frame struct {
		Control      byte   `json:"Control"`
		PacketNumber uint16 `json:"PacketNumber"`
		DeviceTime   string `json:"DeviceTime"`
	}
	_ = json.Unmarshal(envelope.Frame, &frame)
	if frame.DeviceTime != "" {
		if occurred, parseErr := time.Parse(time.RFC3339, frame.DeviceTime); parseErr == nil {
			message.DeviceOccurredAt = &occurred
		}
	}
	err = impl.DBService.Transaction(func(tx *gorm.DB) error {
		if createErr := tx.Create(&message).Error; createErr != nil {
			return createErr
		}
		if envelope.DeviceID == "" || frame.PacketNumber == 0 || frame.Control&0x08 == 0 {
			return nil
		}
		status, errorCode := "succeeded", ""
		if frame.Control&0x04 != 0 {
			status, errorCode = "failed", "DEVICE_REPORTED_FAILURE"
		}
		result := tx.Model(&models.IotCommand{}).Where("device_id = ? AND packet_number = ? AND command_status IN ?", envelope.DeviceID, frame.PacketNumber, []string{"dispatched", "pending_confirmation"}).Updates(map[string]any{"command_status": status, "error_code": errorCode, "acknowledged_at": received, "updated_at": received})
		if result.Error != nil {
			return result.Error
		}
		if result.RowsAffected > 1 {
			return errors.New("ambiguous device acknowledgement")
		}
		return nil
	})
	if err != nil {
		ctx.JSON(500, gin.H{"code": "IOT_MESSAGE_SAVE_FAILED"})
		return
	}
	ctx.JSON(http.StatusAccepted, gin.H{"identity": message.Identity})
}