// Copyright (c) 2025-2026 Probo Inc <hello@probo.com>.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

package validator

import (
	"fmt"
	"net/url"
	"regexp"
	"slices"
	"strings"

	"go.probo.inc/probo/pkg/gid"
)

var (
	domainRegex = regexp.MustCompile(`^(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)*[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?$`)
	slugRegex   = regexp.MustCompile(`^[a-z0-9]+(-[a-z0-9]+)*$`)
)

// URL validates that a string is a valid URL with http or https scheme.
func URL() ValidatorFunc {
	return func(value any) *ValidationError {
		actualValue, isNil := dereferenceValue(value)
		if isNil {
			return nil
		}

		str, ok := actualValue.(string)
		if !ok {
			return newValidationError(ErrorCodeInvalidURL, "value must be a string")
		}

		if str == "" {
			return nil
		}

		parsedURL, err := url.Parse(str)
		if err != nil {
			return newValidationError(ErrorCodeInvalidURL, "invalid URL format")
		}

		if parsedURL.Scheme != "http" && parsedURL.Scheme != "https" {
			return newValidationError(ErrorCodeInvalidURL, "URL must use http or https scheme")
		}

		if parsedURL.Host == "" {
			return newValidationError(ErrorCodeInvalidURL, "URL must have a host")
		}

		return nil
	}
}

// HTTPSUrl validates that a string is a valid HTTPS URL (not HTTP).
func HTTPSUrl() ValidatorFunc {
	return func(value any) *ValidationError {
		actualValue, isNil := dereferenceValue(value)
		if isNil {
			return nil
		}

		str, ok := actualValue.(string)
		if !ok {
			return newValidationError(ErrorCodeInvalidURL, "value must be a string")
		}

		if str == "" {
			return nil
		}

		parsedURL, err := url.Parse(str)
		if err != nil {
			return newValidationError(ErrorCodeInvalidURL, "invalid URL format")
		}

		if parsedURL.Scheme != "https" {
			return newValidationError(ErrorCodeInvalidURL, "URL must use https scheme")
		}

		if parsedURL.Host == "" {
			return newValidationError(ErrorCodeInvalidURL, "URL must have a host")
		}

		return nil
	}
}

// GID validates that a string is a valid GID using gid.ParseGID.
// Optionally validates the entity type if provided.
//
// Example usage:
//   - GID() validates any GID format
//   - GID(100) validates GID with entity type 100
//   - GID(100, 200) validates GID with entity type 100 or 200
func GID(entityTypes ...uint16) ValidatorFunc {
	return func(value any) *ValidationError {
		if value == nil {
			return nil
		}

		var gidValue gid.GID

		switch v := value.(type) {
		case gid.GID:
			gidValue = v
		case *gid.GID:
			if v == nil {
				return nil
			}

			gidValue = *v
		default:
			return newValidationError(ErrorCodeInvalidGID, "value must be a GID")
		}

		if len(entityTypes) > 0 {
			parsedEntityType := gidValue.EntityType()

			valid := slices.Contains(entityTypes, parsedEntityType)
			if !valid {
				return newValidationError(ErrorCodeInvalidGID, "GID has invalid entity type")
			}
		}

		return nil
	}
}

// Origin validates that a string is a valid web origin (scheme + host + optional port).
// No path, query, fragment, or userinfo is allowed.
func Origin() ValidatorFunc {
	return func(value any) *ValidationError {
		actualValue, isNil := dereferenceValue(value)
		if isNil {
			return nil
		}

		str, ok := actualValue.(string)
		if !ok {
			return newValidationError(ErrorCodeInvalidFormat, "value must be a string")
		}

		if str == "" {
			return nil
		}

		parsedURL, err := url.Parse(str)
		if err != nil {
			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
		}

		if parsedURL.Scheme != "http" && parsedURL.Scheme != "https" {
			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
		}

		if parsedURL.Host == "" || parsedURL.Hostname() == "" || strings.HasSuffix(parsedURL.Host, ":") {
			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
		}

		if parsedURL.Path != "" && parsedURL.Path != "/" {
			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
		}

		if parsedURL.RawQuery != "" || parsedURL.Fragment != "" || parsedURL.User != nil {
			return newValidationError(ErrorCodeInvalidFormat, "must be a valid origin (e.g. https://example.com)")
		}

		return nil
	}
}

// Slug validates that a string is a lowercase alphanumeric slug (with hyphens, no
// leading/trailing hyphens, no consecutive hyphens) and does not exceed maxLen.
func Slug(maxLen int) ValidatorFunc {
	return func(value any) *ValidationError {
		actualValue, isNil := dereferenceValue(value)
		if isNil {
			return nil
		}

		str, ok := actualValue.(string)
		if !ok {
			return newValidationError(ErrorCodeInvalidFormat, "value must be a string")
		}

		if str == "" {
			return nil
		}

		if len(str) > maxLen {
			return newValidationError(ErrorCodeTooLong, fmt.Sprintf("slug must be at most %d characters", maxLen))
		}

		if !slugRegex.MatchString(str) {
			return newValidationError(ErrorCodeInvalidFormat, "slug must contain only lowercase letters, numbers, and hyphens")
		}

		return nil
	}
}

// Domain validates that a string is a valid domain name.
func Domain() ValidatorFunc {
	return func(value any) *ValidationError {
		actualValue, isNil := dereferenceValue(value)
		if isNil {
			return nil
		}

		str, ok := actualValue.(string)
		if !ok {
			return newValidationError(ErrorCodeInvalidFormat, "value must be a string")
		}

		if str == "" {
			return nil
		}

		if len(str) > 253 {
			return newValidationError(ErrorCodeInvalidFormat, "domain name too long (max 253 characters)")
		}

		if !domainRegex.MatchString(str) {
			return newValidationError(ErrorCodeInvalidFormat, "invalid domain name format")
		}

		return nil
	}
}