gno.land/p/nt/avl/pager/v0⧉

1package pager23import (4	"math"5	"net/url"6	"strconv"78	"gno.land/p/nt/avl/rotree/v0"9	"gno.land/p/nt/ufmt/v0"10)1112// Pager is a struct that holds the AVL tree and pagination parameters.13type Pager struct {14	Tree            rotree.IReadOnlyTree15	PageQueryParam  string16	SizeQueryParam  string17	DefaultPageSize int18	Reversed        bool19}2021// Page represents a single page of results.22type Page struct {23	Items      []Item24	PageNumber int25	PageSize   int26	TotalItems int27	TotalPages int28	HasPrev    bool29	HasNext    bool30	Pager      *Pager // Reference to the parent Pager31}3233// Item represents a key-value pair in the AVL tree.34type Item struct {35	Key   string36	Value any37}3839// NewPager creates a new Pager with default values.40func NewPager(tree rotree.IReadOnlyTree, defaultPageSize int, reversed bool) *Pager {41	return &Pager{42		Tree:            tree,43		PageQueryParam:  "page",44		SizeQueryParam:  "size",45		DefaultPageSize: defaultPageSize,46		Reversed:        reversed,47	}48}4950// GetPage retrieves a page of results from the AVL tree.51func (p *Pager) GetPage(pageNumber int) *Page {52	return p.GetPageWithSize(pageNumber, p.DefaultPageSize)53}5455func (p *Pager) GetPageWithSize(pageNumber, pageSize int) *Page {56	if pageSize <= 0 {57		panic("GetPageWithSize: invalid page size")58	}5960	totalItems := p.Tree.Size()61	totalPages := int(math.Ceil(float64(totalItems) / float64(pageSize)))6263	page := &Page{64		TotalItems: totalItems,65		TotalPages: totalPages,66		PageSize:   pageSize,67		Pager:      p,68	}6970	// page number provided is not available71	if pageNumber < 1 {72		page.HasNext = totalPages > 073		return page74	}7576	// page number provided is outside the range of total pages77	if pageNumber > totalPages {78		page.PageNumber = pageNumber79		page.HasPrev = pageNumber > 080		return page81	}8283	startIndex := (pageNumber - 1) * pageSize84	endIndex := startIndex + pageSize85	if endIndex > totalItems {86		endIndex = totalItems87	}8889	items := []Item{}9091	if p.Reversed {92		p.Tree.ReverseIterateByOffset(startIndex, endIndex-startIndex, func(key string, value any) bool {93			items = append(items, Item{Key: key, Value: value})94			return false95		})96	} else {97		p.Tree.IterateByOffset(startIndex, endIndex-startIndex, func(key string, value any) bool {98			items = append(items, Item{Key: key, Value: value})99			return false100		})101	}102103	page.Items = items104	page.PageNumber = pageNumber105	page.HasPrev = pageNumber > 1106	page.HasNext = pageNumber < totalPages107	return page108}109110func (p *Pager) MustGetPageByPath(rawURL string) *Page {111	page, err := p.GetPageByPath(rawURL)112	if err != nil {113		panic("invalid path")114	}115	return page116}117118// GetPageByPath retrieves a page of results based on the query parameters in the URL path.119func (p *Pager) GetPageByPath(rawURL string) (*Page, error) {120	pageNumber, pageSize, err := p.ParseQuery(rawURL)121	if err != nil {122		return nil, err123	}124	return p.GetPageWithSize(pageNumber, pageSize), nil125}126127// Picker generates the Markdown UI for the page Picker128func (p *Page) Picker(path string) string {129	pageNumber := p.PageNumber130	pageNumber = max(pageNumber, 1)131132	if p.TotalPages <= 1 {133		return ""134	}135136	u, _ := url.Parse(path)137	query := u.Query()138139	// Remove existing page query parameter140	query.Del(p.Pager.PageQueryParam)141142	// Encode remaining query parameters143	baseQuery := query.Encode()144	if baseQuery != "" {145		baseQuery = "&" + baseQuery146	}147	md := ""148149	if p.HasPrev {150		md += ufmt.Sprintf("[%d](?%s=%d%s) | ", 1, p.Pager.PageQueryParam, 1, baseQuery)151152		if p.PageNumber > 4 {153			md += "… | "154		}155156		if p.PageNumber > 3 {157			md += ufmt.Sprintf("[%d](?%s=%d%s) | ", p.PageNumber-2, p.Pager.PageQueryParam, p.PageNumber-2, baseQuery)158		}159160		if p.PageNumber > 2 {161			md += ufmt.Sprintf("[%d](?%s=%d%s) | ", p.PageNumber-1, p.Pager.PageQueryParam, p.PageNumber-1, baseQuery)162		}163	}164165	if p.PageNumber > 0 && p.PageNumber <= p.TotalPages {166		md += ufmt.Sprintf("**%d**", p.PageNumber)167	} else {168		md += ufmt.Sprintf("_%d_", p.PageNumber)169	}170171	if p.HasNext {172		if p.PageNumber < p.TotalPages-1 {173			md += ufmt.Sprintf(" | [%d](?%s=%d%s)", p.PageNumber+1, p.Pager.PageQueryParam, p.PageNumber+1, baseQuery)174		}175176		if p.PageNumber < p.TotalPages-2 {177			md += ufmt.Sprintf(" | [%d](?%s=%d%s)", p.PageNumber+2, p.Pager.PageQueryParam, p.PageNumber+2, baseQuery)178		}179180		if p.PageNumber < p.TotalPages-3 {181			md += " | …"182		}183184		md += ufmt.Sprintf(" | [%d](?%s=%d%s)", p.TotalPages, p.Pager.PageQueryParam, p.TotalPages, baseQuery)185	}186187	return md188}189190// ParseQuery parses the URL to extract the page number and page size.191func (p *Pager) ParseQuery(rawURL string) (int, int, error) {192	u, err := url.Parse(rawURL)193	if err != nil {194		return 1, p.DefaultPageSize, err195	}196197	query := u.Query()198	pageNumber := 1199	pageSize := p.DefaultPageSize200201	if p.PageQueryParam != "" {202		if pageStr := query.Get(p.PageQueryParam); pageStr != "" {203			pageNumber, err = strconv.Atoi(pageStr)204			if err != nil || pageNumber < 1 {205				pageNumber = 1206			}207		}208	}209210	if p.SizeQueryParam != "" {211		if sizeStr := query.Get(p.SizeQueryParam); sizeStr != "" {212			pageSize, err = strconv.Atoi(sizeStr)213			if err != nil || pageSize < 1 {214				pageSize = p.DefaultPageSize215			}216		}217	}218219	return pageNumber, pageSize, nil220}221222func max(a, b int) int {223	if a > b {224		return a225	}226	return b227}228