package playletser

import (
	"strconv"
	"strings"
)

const defaultThemeIndexPageSize = 20

// ThemeIndexQuery 专题列表页分页参数。
type ThemeIndexQuery struct {
	PageNum  int
	PageSize int
}

func (q *ThemeIndexQuery) Normalize() {
	if q.PageNum <= 0 {
		q.PageNum = 1
	}
	if q.PageSize <= 0 {
		q.PageSize = defaultThemeIndexPageSize
	}
}

// ParseThemeIndexQuery 从语义化分页路由读取页码。
func ParseThemeIndexQuery(page string) ThemeIndexQuery {
	q := ThemeIndexQuery{PageSize: defaultThemeIndexPageSize}
	if n, err := strconv.Atoi(strings.TrimSpace(page)); err == nil {
		q.PageNum = n
	}
	q.Normalize()
	return q
}

// BuildThemeIndexPage 过滤已启用专题，并按设计稿每页 20 项分页。
func BuildThemeIndexPage(themes []PlayletThemeItem, q ThemeIndexQuery) ([]PlayletThemeItem, int64) {
	q.Normalize()
	visible := make([]PlayletThemeItem, 0, len(themes))
	for _, theme := range themes {
		if !theme.Status || theme.ID <= 0 || strings.TrimSpace(theme.Name) == "" {
			continue
		}
		visible = append(visible, theme)
	}
	total := int64(len(visible))
	start := (q.PageNum - 1) * q.PageSize
	if start >= len(visible) {
		return nil, total
	}
	end := start + q.PageSize
	if end > len(visible) {
		end = len(visible)
	}
	return visible[start:end], total
}

func themeIndexPageURL(page int) string {
	if page <= 1 {
		return "/topic/"
	}
	return "/topic/page/" + strconv.Itoa(page) + "/"
}

func ThemeIndexCanonicalPath(q ThemeIndexQuery) string {
	q.Normalize()
	return themeIndexPageURL(q.PageNum)
}

func BuildThemeIndexPagination(q ThemeIndexQuery, totalCount int64) PaginationVM {
	q.Normalize()
	return BuildPagination(themeIndexPageURL, q.PageNum, q.PageSize, totalCount)
}