package validator

import (
	"fmt"
	"regexp"
	"strings"

	"github.com/bluesky-social/indigo/atproto/syntax"
	"golang.org/x/exp/slices"
	"tangled.sh/tangled.sh/core/api/tangled"
	"tangled.sh/tangled.sh/core/appview/db"
)

var (
	// Label name should be alphanumeric with hyphens/underscores, but not start/end with them
	labelNameRegex = regexp.MustCompile(`^[a-zA-Z0-9]([a-zA-Z0-9_-]*[a-zA-Z0-9])?$`)
	// Color should be a valid hex color
	colorRegex = regexp.MustCompile(`^#[a-fA-F0-9]{6}$`)
	// You can only label issues and pulls presently
	validScopes = []syntax.NSID{tangled.RepoIssueNSID, tangled.RepoPullNSID}
)

func (v *Validator) ValidateLabelDefinition(label *db.LabelDefinition) error {
	if label.Name == "" {
		return fmt.Errorf("label name is empty")
	}
	if len(label.Name) > 40 {
		return fmt.Errorf("label name too long (max 40 graphemes)")
	}
	if len(label.Name) < 1 {
		return fmt.Errorf("label name too short (min 1 grapheme)")
	}
	if !labelNameRegex.MatchString(label.Name) {
		return fmt.Errorf("label name contains invalid characters (use only letters, numbers, hyphens, and underscores)")
	}

	if !label.ValueType.IsConcreteType() {
		return fmt.Errorf("invalid value type: %q (must be one of: null, boolean, integer, string)", label.ValueType)
	}

	if label.ValueType.IsNull() && label.ValueType.IsEnumType() {
		return fmt.Errorf("null type cannot be used in conjunction with enum type")
	}

	// validate scope (nsid format)
	if label.Scope == "" {
		return fmt.Errorf("scope is required")
	}
	if _, err := syntax.ParseNSID(string(label.Scope)); err != nil {
		return fmt.Errorf("failed to parse scope: %w", err)
	}
	if !slices.Contains(validScopes, label.Scope) {
		return fmt.Errorf("invalid scope: scope must be one of %q", validScopes)
	}

	// validate color if provided
	if label.Color != nil {
		color := strings.TrimSpace(*label.Color)
		if color == "" {
			// empty color is fine, set to nil
			label.Color = nil
		} else {
			if !colorRegex.MatchString(color) {
				return fmt.Errorf("color must be a valid hex color (e.g. #79FFE1 or #000)")
			}
			// expand 3-digit hex to 6-digit hex
			if len(color) == 4 { // #ABC
				color = fmt.Sprintf("#%c%c%c%c%c%c", color[1], color[1], color[2], color[2], color[3], color[3])
			}
			// convert to uppercase for consistency
			color = strings.ToUpper(color)
			label.Color = &color
		}
	}

	return nil
}