package utils

import (
	"fmt"
	"strconv"
	"strings"
)

// ValidationError represents a validation error with field name
type ValidationError struct {
	Field   string
	Message string
}

func (e *ValidationError) Error() string {
	return fmt.Sprintf("%s: %s", e.Field, e.Message)
}

// ValidateBookFields validates all book form fields
func ValidateBookFields(bookName, cost, price, discount, quantity, publisherAuthor, category, description string) []*ValidationError {
	var errors []*ValidationError

	// Book Name
	bookName = strings.TrimSpace(bookName)
	if bookName == "" {
		errors = append(errors, &ValidationError{Field: "book_name", Message: "is required"})
	} else if len(bookName) > 200 {
		errors = append(errors, &ValidationError{Field: "book_name", Message: "exceeds 200 characters"})
	}

	// Cost
	if cost == "" {
		errors = append(errors, &ValidationError{Field: "cost", Message: "is required"})
	} else {
		costVal, err := strconv.ParseFloat(cost, 64)
		if err != nil || costVal <= 0 {
			errors = append(errors, &ValidationError{Field: "cost", Message: "must be a positive number"})
		}
	}

	// Price
	if price == "" {
		errors = append(errors, &ValidationError{Field: "price", Message: "is required"})
	} else {
		priceVal, err := strconv.ParseFloat(price, 64)
		if err != nil || priceVal <= 0 {
			errors = append(errors, &ValidationError{Field: "price", Message: "must be a positive number"})
		}
	}

	// Discount (optional)
	if discount != "" {
		discountVal, err := strconv.ParseFloat(discount, 64)
		if err != nil || discountVal < 0 {
			errors = append(errors, &ValidationError{Field: "discount", Message: "must be a non-negative number"})
		}
	}

	// Quantity
	if quantity == "" {
		errors = append(errors, &ValidationError{Field: "quantity", Message: "is required"})
	} else {
		quantityVal, err := strconv.Atoi(quantity)
		if err != nil || quantityVal <= 0 {
			errors = append(errors, &ValidationError{Field: "quantity", Message: "must be a positive integer"})
		}
	}

	// Publisher/Author
	publisherAuthor = strings.TrimSpace(publisherAuthor)
	if publisherAuthor == "" {
		errors = append(errors, &ValidationError{Field: "publisher_author", Message: "is required"})
	} else if len(publisherAuthor) > 200 {
		errors = append(errors, &ValidationError{Field: "publisher_author", Message: "exceeds 200 characters"})
	}

	// Category
	category = strings.TrimSpace(category)
	if category == "" {
		errors = append(errors, &ValidationError{Field: "category", Message: "is required"})
	} else if len(category) > 100 {
		errors = append(errors, &ValidationError{Field: "category", Message: "exceeds 100 characters"})
	}

	// Description (optional)
	if description != "" && len(description) > 1000 {
		errors = append(errors, &ValidationError{Field: "description", Message: "exceeds 1000 characters"})
	}

	return errors
}

// ValidateStationeryFields validates all stationery form fields
func ValidateStationeryFields(stationeryName, cost, price, discount, quantity, category, description string) []*ValidationError {
	var errors []*ValidationError

	// Stationery Name
	stationeryName = strings.TrimSpace(stationeryName)
	if stationeryName == "" {
		errors = append(errors, &ValidationError{Field: "stationery_name", Message: "is required"})
	} else if len(stationeryName) > 200 {
		errors = append(errors, &ValidationError{Field: "stationery_name", Message: "exceeds 200 characters"})
	}

	// Cost
	if cost == "" {
		errors = append(errors, &ValidationError{Field: "cost", Message: "is required"})
	} else {
		costVal, err := strconv.ParseFloat(cost, 64)
		if err != nil || costVal <= 0 {
			errors = append(errors, &ValidationError{Field: "cost", Message: "must be a positive number"})
		}
	}

	// Price
	if price == "" {
		errors = append(errors, &ValidationError{Field: "price", Message: "is required"})
	} else {
		priceVal, err := strconv.ParseFloat(price, 64)
		if err != nil || priceVal <= 0 {
			errors = append(errors, &ValidationError{Field: "price", Message: "must be a positive number"})
		}
	}

	// Discount (optional)
	if discount != "" {
		discountVal, err := strconv.ParseFloat(discount, 64)
		if err != nil || discountVal < 0 {
			errors = append(errors, &ValidationError{Field: "discount", Message: "must be a non-negative number"})
		}
	}

	// Quantity
	if quantity == "" {
		errors = append(errors, &ValidationError{Field: "quantity", Message: "is required"})
	} else {
		quantityVal, err := strconv.Atoi(quantity)
		if err != nil || quantityVal <= 0 {
			errors = append(errors, &ValidationError{Field: "quantity", Message: "must be a positive integer"})
		}
	}

	// Category
	category = strings.TrimSpace(category)
	if category == "" {
		errors = append(errors, &ValidationError{Field: "category", Message: "is required"})
	} else if len(category) > 100 {
		errors = append(errors, &ValidationError{Field: "category", Message: "exceeds 100 characters"})
	}

	// Description (optional)
	if description != "" && len(description) > 1000 {
		errors = append(errors, &ValidationError{Field: "description", Message: "exceeds 1000 characters"})
	}

	return errors
}

// ValidateFileType checks if file type is allowed
func ValidateFileType(contentType string) error {
	allowedTypes := map[string]bool{
		"image/png":  true,
		"image/jpeg": true,
		"image/jpg":  true,
		"image/webp": true,
	}

	if !allowedTypes[contentType] {
		return fmt.Errorf("invalid file type. Only PNG, JPEG, and WEBP are allowed")
	}

	return nil
}

// ValidateFileSize checks if file size is within limit
func ValidateFileSize(size, maxSize int64) error {
	if size > maxSize {
		return fmt.Errorf("file size exceeds %dMB limit", maxSize/(1024*1024))
	}

	return nil
}