package monitoring

import (
	"net/http"

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
)

// HealthStatus 健康状态
type HealthStatus string

const (
	HealthStatusUP      HealthStatus = "UP"
	HealthStatusDOWN    HealthStatus = "DOWN"
	HealthStatusUNKNOWN HealthStatus = "UNKNOWN"
)

// HealthCheck 健康检查器
type HealthCheck struct {
	db *gorm.DB
}

// NewHealthCheck 创建健康检查器
func NewHealthCheck(db *gorm.DB) *HealthCheck {
	return &HealthCheck{db: db}
}

// Status 健康状态
type Status struct {
	Status HealthStatus           `json:"status"`
	Checks map[string]CheckResult `json:"checks"`
}

// CheckResult 检查结果
type CheckResult struct {
	Status HealthStatus `json:"status"`
	Error  string       `json:"error,omitempty"`
}

// Check 执行健康检查
func (h *HealthCheck) Check() *Status {
	status := &Status{
		Status: HealthStatusUP,
		Checks: make(map[string]CheckResult),
	}

	// 检查数据库
	dbResult := h.checkDatabase()
	status.Checks["database"] = dbResult
	if dbResult.Status != HealthStatusUP {
		status.Status = HealthStatusDOWN
	}

	return status
}

// checkDatabase 检查数据库
func (h *HealthCheck) checkDatabase() CheckResult {
	if h == nil || h.db == nil {
		return CheckResult{
			Status: HealthStatusDOWN,
			Error:  "database not configured",
		}
	}

	sqlDB, err := h.db.DB()
	if err != nil {
		return CheckResult{
			Status: HealthStatusDOWN,
			Error:  err.Error(),
		}
	}

	// Ping数据库
	if err := sqlDB.Ping(); err != nil {
		return CheckResult{
			Status: HealthStatusDOWN,
			Error:  err.Error(),
		}
	}

	return CheckResult{Status: HealthStatusUP}
}

// ReadinessHandler reports dependency readiness.
func (h *HealthCheck) ReadinessHandler(c *gin.Context) {
	status := h.Check()

	httpStatus := http.StatusOK
	if status.Status != HealthStatusUP {
		httpStatus = http.StatusServiceUnavailable
	}

	c.JSON(httpStatus, status)
}

// LivenessHandler reports process liveness without dependency checks.
func (h *HealthCheck) LivenessHandler(c *gin.Context) {
	c.Status(http.StatusNoContent)
	c.Writer.WriteHeaderNow()
}

// Handler keeps backward compatibility with the historical /health endpoint.
func (h *HealthCheck) Handler(c *gin.Context) {
	h.ReadinessHandler(c)
}