package handler

import (
	"database/sql"
	"net/http"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
	"github.com/google/uuid"
)

type Handler struct {
	DB        *sql.DB
	JWTSecret string
}

type Device struct {
	ID          uuid.UUID `json:"id" db:"id"`
	Name        string    `json:"name" db:"name"`
	Description string    `json:"description" db:"description"`
	Location    string    `json:"location" db:"location"`
	StatusID    int       `json:"status_id" db:"status_id"`
	CreatedAt   time.Time `json:"created_at" db:"created_at"`
	UpdatedAt   time.Time `json:"updated_at" db:"updated_at"`
}

// Health returns basic service health
func (h *Handler) Health(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{"status": "ok"})
}

// Hello returns a simple greeting
func (h *Handler) Hello(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{"message": "hello from lambda-iot core"})
}

// Login issues a JWT token for demo purposes
func (h *Handler) Login(c *gin.Context) {
	var req struct {
		Username string `json:"username"`
		Password string `json:"password"`
	}
	if err := c.BindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid json"})
		return
	}
	// demo credentials
	if req.Username != "admin" || req.Password != "password" {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "invalid credentials"})
		return
	}
	// create token
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
		"sub": req.Username,
		"exp": time.Now().Add(time.Hour).Unix(),
	})
	signed, err := token.SignedString([]byte(h.JWTSecret))
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "could not sign token"})
		return
	}
	c.JSON(http.StatusOK, gin.H{"token": signed})
}

// CreateDevice creates a new device
func (h *Handler) CreateDevice(c *gin.Context) {
	var req struct {
		Name        string `json:"name" binding:"required"`
		Description string `json:"description" binding:"required"`
		Location    string `json:"location" binding:"required"`
		StatusID    int    `json:"status_id" binding:"required,min=1,max=4"`
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	id := uuid.New()
	_, err := h.DB.Exec("INSERT INTO devices (id, name, description, location, status_id) VALUES (UUID_TO_BIN(?), ?, ?, ?, ?)", id.String(), req.Name, req.Description, req.Location, req.StatusID)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to create device"})
		return
	}

	c.JSON(http.StatusCreated, gin.H{"id": id.String()})
}

// GetDevices retrieves all devices
func (h *Handler) GetDevices(c *gin.Context) {
	rows, err := h.DB.Query("SELECT BIN_TO_UUID(id), name, description, location, status_id, created_at, updated_at FROM devices")
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to fetch devices"})
		return
	}
	defer rows.Close()

	var devices []Device
	for rows.Next() {
		var d Device
		err := rows.Scan(&d.ID, &d.Name, &d.Description, &d.Location, &d.StatusID, &d.CreatedAt, &d.UpdatedAt)
		if err != nil {
			c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to scan device"})
			return
		}
		devices = append(devices, d)
	}

	c.JSON(http.StatusOK, devices)
}

// GetDevice retrieves a single device by ID
func (h *Handler) GetDevice(c *gin.Context) {
	idStr := c.Param("id")
	id, err := uuid.Parse(idStr)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid device id"})
		return
	}

	var d Device
	err = h.DB.QueryRow("SELECT BIN_TO_UUID(id), name, description, location, status_id, created_at, updated_at FROM devices WHERE id = UUID_TO_BIN(?)", id.String()).Scan(&d.ID, &d.Name, &d.Description, &d.Location, &d.StatusID, &d.CreatedAt, &d.UpdatedAt)
	if err == sql.ErrNoRows {
		c.JSON(http.StatusNotFound, gin.H{"error": "device not found"})
		return
	} else if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to fetch device"})
		return
	}

	c.JSON(http.StatusOK, d)
}

// UpdateDevice updates a device
func (h *Handler) UpdateDevice(c *gin.Context) {
	idStr := c.Param("id")
	id, err := uuid.Parse(idStr)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid device id"})
		return
	}

	var req struct {
		Name        *string `json:"name"`
		Description *string `json:"description"`
		Location    *string `json:"location"`
		StatusID    *int    `json:"status_id"`
	}
	if err := c.ShouldBindJSON(&req); err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return
	}

	// Build update query dynamically
	setParts := []string{}
	args := []interface{}{}
	if req.Name != nil {
		setParts = append(setParts, "name = ?")
		args = append(args, *req.Name)
	}
	if req.Description != nil {
		setParts = append(setParts, "description = ?")
		args = append(args, *req.Description)
	}
	if req.Location != nil {
		setParts = append(setParts, "location = ?")
		args = append(args, *req.Location)
	}
	if req.StatusID != nil {
		setParts = append(setParts, "status_id = ?")
		args = append(args, *req.StatusID)
	}
	if len(setParts) == 0 {
		c.JSON(http.StatusBadRequest, gin.H{"error": "no fields to update"})
		return
	}

	query := "UPDATE devices SET " + strings.Join(setParts, ", ") + " WHERE id = UUID_TO_BIN(?)"
	args = append(args, id.String())

	_, err = h.DB.Exec(query, args...)
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to update device"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "device updated"})
}

// DeleteDevice deletes a device
func (h *Handler) DeleteDevice(c *gin.Context) {
	idStr := c.Param("id")
	id, err := uuid.Parse(idStr)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid device id"})
		return
	}

	_, err = h.DB.Exec("DELETE FROM devices WHERE id = UUID_TO_BIN(?)", id.String())
	if err != nil {
		c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to delete device"})
		return
	}

	c.JSON(http.StatusOK, gin.H{"message": "device deleted"})
}

// Protected requires a valid JWT and returns the token claims
func (h *Handler) Protected(c *gin.Context) {
	if v, ok := c.Get("claims"); ok {
		c.JSON(http.StatusOK, gin.H{"claims": v})
		return
	}
	c.JSON(http.StatusUnauthorized, gin.H{"error": "no claims"})
}