package validators

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

	validation "github.com/go-ozzo/ozzo-validation/v4"
	"github.com/go-ozzo/ozzo-validation/v4/is"
	"github.com/pocketbase/dbx"
	"github.com/pocketbase/pocketbase/daos"
	"github.com/pocketbase/pocketbase/models"
	"github.com/pocketbase/pocketbase/models/schema"
	"github.com/pocketbase/pocketbase/tools/list"
	"github.com/pocketbase/pocketbase/tools/rest"
	"github.com/pocketbase/pocketbase/tools/types"
)

var requiredErr = validation.NewError("validation_required", "Missing required value")

// NewRecordDataValidator creates new [models.Record] data validator
// using the provided record constraints and schema.
//
// Example:
//	validator := NewRecordDataValidator(app.Dao(), record, nil)
//	err := validator.Validate(map[string]any{"test":123})
func NewRecordDataValidator(
	dao *daos.Dao,
	record *models.Record,
	uploadedFiles []*rest.UploadedFile,
) *RecordDataValidator {
	return &RecordDataValidator{
		dao:           dao,
		record:        record,
		uploadedFiles: uploadedFiles,
	}
}

// RecordDataValidator defines a  model.Record data validator
// using the provided record constraints and schema.
type RecordDataValidator struct {
	dao           *daos.Dao
	record        *models.Record
	uploadedFiles []*rest.UploadedFile
}

// Validate validates the provided `data` by checking it against
// the validator record constraints and schema.
func (validator *RecordDataValidator) Validate(data map[string]any) error {
	keyedSchema := validator.record.Collection().Schema.AsMap()
	if len(keyedSchema) == 0 {
		return nil // no fields to check
	}

	if len(data) == 0 {
		return validation.NewError("validation_empty_data", "No data to validate")
	}

	errs := validation.Errors{}

	// check for unknown fields
	for key := range data {
		if _, ok := keyedSchema[key]; !ok {
			errs[key] = validation.NewError("validation_unknown_field", "Unknown field")
		}
	}
	if len(errs) > 0 {
		return errs
	}

	for key, field := range keyedSchema {
		// normalize value to emulate the same behavior
		// when fetching or persisting the record model
		value := field.PrepareValue(data[key])

		// check required constraint
		if field.Required && validation.Required.Validate(value) != nil {
			errs[key] = requiredErr
			continue
		}

		// validate field value by its field type
		if err := validator.checkFieldValue(field, value); err != nil {
			errs[key] = err
			continue
		}

		// check unique constraint
		if field.Unique && !validator.dao.IsRecordValueUnique(
			validator.record.Collection(),
			key,
			value,
			validator.record.GetId(),
		) {
			errs[key] = validation.NewError("validation_not_unique", "Value must be unique")
			continue
		}
	}

	if len(errs) == 0 {
		return nil
	}

	return errs
}

func (validator *RecordDataValidator) checkFieldValue(field *schema.SchemaField, value any) error {
	switch field.Type {
	case schema.FieldTypeText:
		return validator.checkTextValue(field, value)
	case schema.FieldTypeNumber:
		return validator.checkNumberValue(field, value)
	case schema.FieldTypeBool:
		return validator.checkBoolValue(field, value)
	case schema.FieldTypeEmail:
		return validator.checkEmailValue(field, value)
	case schema.FieldTypeUrl:
		return validator.checkUrlValue(field, value)
	case schema.FieldTypeDate:
		return validator.checkDateValue(field, value)
	case schema.FieldTypeSelect:
		return validator.checkSelectValue(field, value)
	case schema.FieldTypeJson:
		return validator.checkJsonValue(field, value)
	case schema.FieldTypeFile:
		return validator.checkFileValue(field, value)
	case schema.FieldTypeRelation:
		return validator.checkRelationValue(field, value)
	case schema.FieldTypeUser:
		return validator.checkUserValue(field, value)
	}

	return nil
}

func (validator *RecordDataValidator) checkTextValue(field *schema.SchemaField, value any) error {
	val, _ := value.(string)
	if val == "" {
		return nil // nothing to check
	}

	options, _ := field.Options.(*schema.TextOptions)

	if options.Min != nil && len(val) < *options.Min {
		return validation.NewError("validation_min_text_constraint", fmt.Sprintf("Must be at least %d character(s)", *options.Min))
	}

	if options.Max != nil && len(val) > *options.Max {
		return validation.NewError("validation_max_text_constraint", fmt.Sprintf("Must be less than %d character(s)", *options.Max))
	}

	if options.Pattern != "" {
		match, _ := regexp.MatchString(options.Pattern, val)
		if !match {
			return validation.NewError("validation_invalid_format", "Invalid value format")
		}
	}

	return nil
}

func (validator *RecordDataValidator) checkNumberValue(field *schema.SchemaField, value any) error {
	if value == nil {
		return nil // nothing to check
	}

	val, _ := value.(float64)
	options, _ := field.Options.(*schema.NumberOptions)

	if options.Min != nil && val < *options.Min {
		return validation.NewError("validation_min_number_constraint", fmt.Sprintf("Must be larger than %f", *options.Min))
	}

	if options.Max != nil && val > *options.Max {
		return validation.NewError("validation_max_number_constraint", fmt.Sprintf("Must be less than %f", *options.Max))
	}

	return nil
}

func (validator *RecordDataValidator) checkBoolValue(field *schema.SchemaField, value any) error {
	return nil
}

func (validator *RecordDataValidator) checkEmailValue(field *schema.SchemaField, value any) error {
	val, _ := value.(string)
	if val == "" {
		return nil // nothing to check
	}

	if is.Email.Validate(val) != nil {
		return validation.NewError("validation_invalid_email", "Must be a valid email")
	}

	options, _ := field.Options.(*schema.EmailOptions)
	domain := val[strings.LastIndex(val, "@")+1:]

	// only domains check
	if len(options.OnlyDomains) > 0 && !list.ExistInSlice(domain, options.OnlyDomains) {
		return validation.NewError("validation_email_domain_not_allowed", "Email domain is not allowed")
	}

	// except domains check
	if len(options.ExceptDomains) > 0 && list.ExistInSlice(domain, options.ExceptDomains) {
		return validation.NewError("validation_email_domain_not_allowed", "Email domain is not allowed")
	}

	return nil
}

func (validator *RecordDataValidator) checkUrlValue(field *schema.SchemaField, value any) error {
	val, _ := value.(string)
	if val == "" {
		return nil // nothing to check
	}

	if is.URL.Validate(val) != nil {
		return validation.NewError("validation_invalid_url", "Must be a valid url")
	}

	options, _ := field.Options.(*schema.UrlOptions)

	// extract host/domain
	u, _ := url.Parse(val)
	host := u.Host

	// only domains check
	if len(options.OnlyDomains) > 0 && !list.ExistInSlice(host, options.OnlyDomains) {
		return validation.NewError("validation_url_domain_not_allowed", "Url domain is not allowed")
	}

	// except domains check
	if len(options.ExceptDomains) > 0 && list.ExistInSlice(host, options.ExceptDomains) {
		return validation.NewError("validation_url_domain_not_allowed", "Url domain is not allowed")
	}

	return nil
}

func (validator *RecordDataValidator) checkDateValue(field *schema.SchemaField, value any) error {
	val, _ := value.(types.DateTime)

	if val.IsZero() {
		if field.Required {
			return requiredErr
		}
		return nil // nothing to check
	}

	options, _ := field.Options.(*schema.DateOptions)

	if !options.Min.IsZero() {
		if err := validation.Min(options.Min.Time()).Validate(val.Time()); err != nil {
			return err
		}
	}

	if !options.Max.IsZero() {
		if err := validation.Max(options.Max.Time()).Validate(val.Time()); err != nil {
			return err
		}
	}

	return nil
}

func (validator *RecordDataValidator) checkSelectValue(field *schema.SchemaField, value any) error {
	normalizedVal := list.ToUniqueStringSlice(value)
	if len(normalizedVal) == 0 {
		return nil // nothing to check
	}

	options, _ := field.Options.(*schema.SelectOptions)

	// check max selected items
	if len(normalizedVal) > options.MaxSelect {
		return validation.NewError("validation_too_many_values", fmt.Sprintf("Select no more than %d", options.MaxSelect))
	}

	// check against the allowed values
	for _, val := range normalizedVal {
		if !list.ExistInSlice(val, options.Values) {
			return validation.NewError("validation_invalid_value", "Invalid value "+val)
		}
	}

	return nil
}

func (validator *RecordDataValidator) checkJsonValue(field *schema.SchemaField, value any) error {
	raw, _ := types.ParseJsonRaw(value)
	if len(raw) == 0 {
		return nil // nothing to check
	}

	if is.JSON.Validate(value) != nil {
		return validation.NewError("validation_invalid_json", "Must be a valid json value")
	}

	return nil
}

func (validator *RecordDataValidator) checkFileValue(field *schema.SchemaField, value any) error {
	// normalize value access
	var names []string
	switch v := value.(type) {
	case []string:
		names = v
	case string:
		names = []string{v}
	}

	options, _ := field.Options.(*schema.FileOptions)

	if len(names) > options.MaxSelect {
		return validation.NewError("validation_too_many_values", fmt.Sprintf("Select no more than %d", options.MaxSelect))
	}

	// extract the uploaded files
	files := []*rest.UploadedFile{}
	if len(validator.uploadedFiles) > 0 {
		for _, file := range validator.uploadedFiles {
			if list.ExistInSlice(file.Name(), names) {
				files = append(files, file)
			}
		}
	}

	for _, file := range files {
		// check size
		if err := UploadedFileSize(options.MaxSize)(file); err != nil {
			return err
		}

		// check type
		if len(options.MimeTypes) > 0 {
			if err := UploadedFileMimeType(options.MimeTypes)(file); err != nil {
				return err
			}
		}
	}

	return nil
}

func (validator *RecordDataValidator) checkRelationValue(field *schema.SchemaField, value any) error {
	// normalize value access
	var ids []string
	switch v := value.(type) {
	case []string:
		ids = v
	case string:
		ids = []string{v}
	}

	if len(ids) == 0 {
		return nil // nothing to check
	}

	options, _ := field.Options.(*schema.RelationOptions)

	if len(ids) > options.MaxSelect {
		return validation.NewError("validation_too_many_values", fmt.Sprintf("Select no more than %d", options.MaxSelect))
	}

	// check if the related records exist
	// ---
	relCollection, err := validator.dao.FindCollectionByNameOrId(options.CollectionId)
	if err != nil {
		return validation.NewError("validation_missing_rel_collection", "Relation connection is missing or cannot be accessed")
	}

	var total int
	validator.dao.RecordQuery(relCollection).
		Select("count(*)").
		AndWhere(dbx.In("id", list.ToInterfaceSlice(ids)...)).
		Row(&total)
	if total != len(ids) {
		return validation.NewError("validation_missing_rel_records", "Failed to fetch all relation records with the provided ids")
	}
	// ---

	return nil
}

func (validator *RecordDataValidator) checkUserValue(field *schema.SchemaField, value any) error {
	// normalize value access
	var ids []string
	switch v := value.(type) {
	case []string:
		ids = v
	case string:
		ids = []string{v}
	}

	if len(ids) == 0 {
		return nil // nothing to check
	}

	options, _ := field.Options.(*schema.UserOptions)

	if len(ids) > options.MaxSelect {
		return validation.NewError("validation_too_many_values", fmt.Sprintf("Select no more than %d", options.MaxSelect))
	}

	// check if the related users exist
	var total int
	validator.dao.UserQuery().
		Select("count(*)").
		AndWhere(dbx.In("id", list.ToInterfaceSlice(ids)...)).
		Row(&total)
	if total != len(ids) {
		return validation.NewError("validation_missing_users", "Failed to fetch all users with the provided ids")
	}

	return nil
}