package middleware

import (
	"net/http"
	"strconv"

	"github.com/gin-gonic/gin"
	"go.uber.org/zap"
	"veza-backend-api/internal/validators"
)

// QueryParamValidation middleware pour valider les paramètres de requête (BE-SVC-020)
type QueryParamValidation struct {
	logger    *zap.Logger
	validator *validators.Validator
}

// NewQueryParamValidation crée un nouveau middleware de validation des paramètres de requête
func NewQueryParamValidation(logger *zap.Logger) *QueryParamValidation {
	return &QueryParamValidation{
		logger:    logger,
		validator: validators.NewValidator(),
	}
}

// ValidateQueryParams valide les paramètres de requête selon les règles spécifiées
// Usage:
//   router.GET("/users", queryValidation.ValidateQueryParams(map[string]string{
//     "page": "numeric,min=1",
//     "limit": "numeric,min=1,max=100",
//     "sort": "oneof=asc,desc",
//   }), handler)
func (q *QueryParamValidation) ValidateQueryParams(rules map[string]string) gin.HandlerFunc {
	return func(c *gin.Context) {
		errors := make(map[string]string)

		for param, rule := range rules {
			value := c.Query(param)
			if value == "" {
				// Si le paramètre est requis, on vérifie avec "required" dans la règle
				if containsRule(rule, "required") {
					errors[param] = "This query parameter is required"
				}
				continue
			}

			// Valider selon les règles
			if err := q.validateParam(param, value, rule); err != nil {
				errors[param] = err.Error()
			}
		}

		if len(errors) > 0 {
			q.logger.Warn("Query parameter validation failed",
				zap.Any("errors", errors),
				zap.String("path", c.Request.URL.Path),
			)
			c.JSON(http.StatusBadRequest, gin.H{
				"error":   "Invalid query parameters",
				"details": errors,
			})
			c.Abort()
			return
		}

		c.Next()
	}
}

// validateParam valide un paramètre selon une règle
func (q *QueryParamValidation) validateParam(param, value, rule string) error {
	rules := parseRules(rule)

	for _, r := range rules {
		switch r.name {
		case "numeric":
			if _, err := strconv.ParseFloat(value, 64); err != nil {
				return &ValidationError{Field: param, Message: "must be a numeric value"}
			}
		case "integer":
			if _, err := strconv.Atoi(value); err != nil {
				return &ValidationError{Field: param, Message: "must be an integer"}
			}
		case "min":
			if num, err := strconv.ParseFloat(value, 64); err == nil {
				if min, err2 := strconv.ParseFloat(r.param, 64); err2 == nil {
					if num < min {
						return &ValidationError{Field: param, Message: "must be at least " + r.param}
					}
				}
			}
		case "max":
			if num, err := strconv.ParseFloat(value, 64); err == nil {
				if max, err2 := strconv.ParseFloat(r.param, 64); err2 == nil {
					if num > max {
						return &ValidationError{Field: param, Message: "must be at most " + r.param}
					}
				}
			}
		case "oneof":
			validValues := splitComma(r.param)
			found := false
			for _, valid := range validValues {
				valid = trimSpace(valid)
				if value == valid {
					found = true
					break
				}
			}
			if !found {
				return &ValidationError{Field: param, Message: "must be one of: " + r.param}
			}
		case "email":
			if err := q.validator.ValidateVar(value, "email"); err != nil {
				return &ValidationError{Field: param, Message: "must be a valid email address"}
			}
		case "uuid":
			if err := q.validator.ValidateVar(value, "uuid"); err != nil {
				return &ValidationError{Field: param, Message: "must be a valid UUID"}
			}
		case "url":
			if err := q.validator.ValidateVar(value, "url"); err != nil {
				return &ValidationError{Field: param, Message: "must be a valid URL"}
			}
		}
	}

	return nil
}

// ValidationError représente une erreur de validation
type ValidationError struct {
	Field   string
	Message string
}

func (e *ValidationError) Error() string {
	return e.Message
}

// rule représente une règle de validation
type rule struct {
	name  string
	param string
}

// parseRules parse une chaîne de règles (ex: "numeric,min=1,max=100")
func parseRules(ruleStr string) []rule {
	var rules []rule
	parts := splitComma(ruleStr)
	for _, part := range parts {
		part = trimSpace(part)
		if idx := indexOf(part, "="); idx != -1 {
			rules = append(rules, rule{
				name:  part[:idx],
				param: part[idx+1:],
			})
		} else {
			rules = append(rules, rule{
				name:  part,
				param: "",
			})
		}
	}
	return rules
}

// Helper functions
func containsRule(ruleStr, ruleName string) bool {
	rules := parseRules(ruleStr)
	for _, r := range rules {
		if r.name == ruleName {
			return true
		}
	}
	return false
}

func splitComma(s string) []string {
	var result []string
	start := 0
	for i, char := range s {
		if char == ',' {
			if i > start {
				result = append(result, s[start:i])
			}
			start = i + 1
		}
	}
	if start < len(s) {
		result = append(result, s[start:])
	}
	return result
}

func trimSpace(s string) string {
	start := 0
	end := len(s)
	for start < end && s[start] == ' ' {
		start++
	}
	for end > start && s[end-1] == ' ' {
		end--
	}
	return s[start:end]
}

func indexOf(s string, substr string) int {
	for i := 0; i <= len(s)-len(substr); i++ {
		if s[i:i+len(substr)] == substr {
			return i
		}
	}
	return -1
}