package admin

import (
	"context"
	"encoding/json"
	"errors"
	"regexp"
	"strings"
	"unicode/utf8"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"

	"github.com/yuxingu/digital-psychology/apps/api/internal/repository"
)

var (
	ErrInvalidBanner   = errors.New("invalid banner")
	ErrBannerConflict  = errors.New("banner code conflict")
	bannerPathRe       = regexp.MustCompile(`^/[a-zA-Z0-9_./-]{1,200}$`)
	bannerPlacements   = map[string]struct{}{"home": {}, "explore": {}, "ask": {}}
	bannerCodeRe       = regexp.MustCompile(`^[a-z][a-z0-9_]{1,62}$`)
)

// BannerWriteBody is JSON for create/update.
type BannerWriteBody struct {
	Code      string  `json:"code"`
	Title     string  `json:"title"`
	Placement string  `json:"placement"`
	ImageURL  *string `json:"image_url"`
	LinkPath  *string `json:"link_path"`
	SortOrder int     `json:"sort_order"`
	Active    bool    `json:"active"`
}

// CreateBanner validates, inserts, audits.
func (s *Service) CreateBanner(ctx context.Context, adminID uuid.UUID, body BannerWriteBody) (*repository.BannerRow, error) {
	in, err := normalizeBannerWrite(body, true)
	if err != nil {
		return nil, err
	}
	meta, _ := json.Marshal(map[string]any{"code": in.Code, "active": in.Active})
	row, err := s.Repo.CreateBannerWithAudit(ctx, adminID, in, meta)
	if repository.BannerCodeConflict(err) {
		return nil, ErrBannerConflict
	}
	return row, err
}

// UpdateBanner validates, updates, audits.
func (s *Service) UpdateBanner(ctx context.Context, adminID, id uuid.UUID, body BannerWriteBody) (*repository.BannerRow, error) {
	in, err := normalizeBannerWrite(body, true)
	if err != nil {
		return nil, err
	}
	meta, _ := json.Marshal(map[string]any{"code": in.Code, "active": in.Active})
	row, err := s.Repo.UpdateBannerWithAudit(ctx, adminID, id, in, meta)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, ErrBannerNotFound
	}
	if repository.BannerCodeConflict(err) {
		return nil, ErrBannerConflict
	}
	return row, err
}

func normalizeBannerWrite(body BannerWriteBody, requireCode bool) (repository.BannerWriteInput, error) {
	code := strings.TrimSpace(body.Code)
	title := strings.TrimSpace(body.Title)
	placement := strings.TrimSpace(body.Placement)
	if requireCode && code == "" {
		return repository.BannerWriteInput{}, ErrInvalidBanner
	}
	if code != "" && !bannerCodeRe.MatchString(code) {
		return repository.BannerWriteInput{}, ErrInvalidBanner
	}
	if title == "" || utf8.RuneCountInString(title) > 128 {
		return repository.BannerWriteInput{}, ErrInvalidBanner
	}
	if _, ok := bannerPlacements[placement]; !ok {
		return repository.BannerWriteInput{}, ErrInvalidBanner
	}
	var link *string
	if body.LinkPath != nil {
		lp := strings.TrimSpace(*body.LinkPath)
		if lp == "" {
			link = nil
		} else {
			if strings.Contains(lp, "://") || !bannerPathRe.MatchString(lp) {
				return repository.BannerWriteInput{}, ErrInvalidBanner
			}
			link = &lp
		}
	}
	var img *string
	if body.ImageURL != nil {
		u := strings.TrimSpace(*body.ImageURL)
		if u == "" {
			img = nil
		} else if utf8.RuneCountInString(u) > 2000 {
			return repository.BannerWriteInput{}, ErrInvalidBanner
		} else {
			img = &u
		}
	}
	return repository.BannerWriteInput{
		Code: code, Title: title, Placement: placement,
		ImageURL: img, LinkPath: link, SortOrder: body.SortOrder, Active: body.Active,
	}, nil
}