pdfdoc: page markers, the map for long documents, page ranges, grep
Pure render function on a *pdftext.Doc with no I/O: the whole text with page markers when it fits, otherwise a map (title, outline with page numbers, leading pages and how to ask for more), a page range, or grep results with page numbers. Every length is in runes. Co-Authored-By: ornith-1.5-35b-a3b <ornith-1.5-35b-a3b@llama.cpp.invalid>
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ornith-1.5-35b-a3b
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// Package pdfdoc renders an extracted document for an agent: the whole text with
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// page markers when it fits, otherwise a map (title, outline with page numbers,
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// leading pages and how to ask for more), a page range, or grep results with page
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// numbers. It works on a *pdftext.Doc with no I/O; every length is in runes, which
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// is what bounds an agent's context regardless of the byte width of a code point.
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package pdfdoc
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import (
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"errors"
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"fmt"
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"strconv"
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"strings"
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"unicode/utf8"
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"git.wntrmute.dev/kyle/sift/internal/pdftext"
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)
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// The errors Render returns for a malformed Pages or Grep option.
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var (
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ErrBadPages = errors.New("invalid pages")
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ErrBadGrep = errors.New("invalid grep")
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)
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// maxPages bounds a range request so a caller cannot ask for the whole of a
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// million-page document at once; the cap below still applies on top of it.
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const maxPages = 100
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// Options selects how Render draws from a document.
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type Options struct {
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Pages string // "" = no range; "a-b", "a" or "a-" (1-based, inclusive)
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Grep string // "" = no grep; an RE2 pattern
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OutCap int // characters (runes) the content may use
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}
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// Rendered is what an agent sees. When Map is true Content is the map of a
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// document longer than OutCap; a grep answer sets GrepHits and leaves First and
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// Last at zero.
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type Rendered struct {
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Content string
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Map bool // Content is the map of a document longer than OutCap
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First, Last int // pages whose text is in Content; 0, 0 for a grep answer
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GrepHits int // matches found (more may exist than are shown)
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Note string // "" or how the answer was cut and how to continue
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}
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// Marker is the header printed before a page's text.
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func Marker(page int) string {
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return fmt.Sprintf("--- page %d ---", page)
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}
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// Full renders every extracted page with its marker, trimmed of surrounding
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// whitespace. It is the unit the map and page ranges are built from.
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func Full(doc *pdftext.Doc) string {
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parts := make([]string, 0, len(doc.Text))
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for i := range doc.Text {
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parts = append(parts, Marker(i+1)+"\n\n"+strings.TrimSpace(doc.Text[i]))
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}
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return strings.Join(parts, "\n\n")
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}
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// Render dispatches on the option that is set: grep, a page range, or the whole
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// document.
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func Render(doc *pdftext.Doc, opt Options) (Rendered, error) {
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switch {
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case opt.Grep != "":
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return renderGrep(doc, opt)
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case opt.Pages != "":
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return renderPages(doc, opt)
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default:
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return renderWhole(doc, opt)
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}
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}
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// renderWhole shows the whole document when it fits OutCap, otherwise a map that
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// fits.
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func renderWhole(doc *pdftext.Doc, opt Options) (Rendered, error) {
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full := Full(doc)
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if utf8.RuneCountInString(full) <= opt.OutCap {
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return Rendered{Content: full, First: 1, Last: len(doc.Text)}, nil
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}
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return renderMap(doc, opt), nil
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}
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// header is the fixed top of a map: the title line and the pages/token line,
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// which notes how many pages were extracted when fewer than the document has.
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func header(doc *pdftext.Doc) string {
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title := doc.Title
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if title == "" {
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title = "Untitled PDF"
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}
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pages := fmt.Sprintf("%d pages · ~%d tokens", doc.Pages, tokenEstimate(doc))
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if len(doc.Text) < doc.Pages {
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pages += fmt.Sprintf(" · pages 1-%d extracted", len(doc.Text))
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}
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return "# " + title + "\n\n" + pages + "\n\n"
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}
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// tokenEstimate roughs a document's size in tokens as a quarter of its runes.
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func tokenEstimate(doc *pdftext.Doc) int {
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return utf8.RuneCountInString(Full(doc)) / 4
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}
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// instruction is the fixed line that tells the agent how to ask for more.
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const instruction = "This document is longer than one answer: ask for pages=\"a-b\" or grep=\"pattern\".\n\n"
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// renderMap assembles the header, a cuttable outline, the instruction, and whole
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// leading pages that fit in a quarter of the cap.
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func renderMap(doc *pdftext.Doc, opt Options) Rendered {
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h := header(doc)
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outlineLines := outlineItems(doc.Outline)
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// The outline is the only flexible part: cut it rather than the header or the
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// instruction when the document's outline would not fit.
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pagesBudget := opt.OutCap / 4
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outlineBudget := opt.OutCap - utf8.RuneCountInString(h) - utf8.RuneCountInString(instruction) - pagesBudget
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if outlineBudget < 0 {
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outlineBudget = 0
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}
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var kept []string
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running := 0
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for _, line := range outlineLines {
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line += "\n"
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if running+utf8.RuneCountInString(line) > outlineBudget {
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break
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}
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running += utf8.RuneCountInString(line)
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kept = append(kept, strings.TrimRight(line, "\n"))
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}
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outlineSection := ""
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if len(kept) > 0 {
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outlineSection = "## Outline\n" + strings.Join(kept, "\n") + "\n\n"
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}
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pages := leadingPages(doc, opt.OutCap-utf8.RuneCountInString(h)-utf8.RuneCountInString(outlineSection)-utf8.RuneCountInString(instruction), pagesBudget)
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content := h + outlineSection + instruction + pages.text
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if utf8.RuneCountInString(content) > opt.OutCap {
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content = truncateRunes(content, opt.OutCap)
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}
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return Rendered{Content: content, Map: true, First: 1, Last: pages.last}
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}
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// outlineItems renders each outline item as "- <indent><title> (p. <page>)", two
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// spaces of indent per level below the top.
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func outlineItems(items []pdftext.OutlineItem) []string {
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lines := make([]string, 0, len(items))
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for _, it := range items {
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indent := strings.Repeat(" ", max(0, (it.Level-1)*2))
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lines = append(lines, indent+"- "+it.Title+" (p. "+strconv.Itoa(it.Page)+")")
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}
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return lines
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}
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// pagesResult is a run of whole pages plus the last one shown.
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type pagesResult struct {
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text string
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last int
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}
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// leadingPages renders whole pages from page 1 into budget runes, at least one,
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// cutting the first to fit if it is alone larger than the budget.
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func leadingPages(doc *pdftext.Doc, budget, pagesBudget int) pagesResult {
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if budget < 0 {
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budget = 0
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}
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if pagesBudget > budget {
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pagesBudget = budget
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}
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extracted := len(doc.Text)
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var parts []string
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running := 0
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last := 0
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for p := 1; p <= extracted; p++ {
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part := Marker(p) + "\n\n" + strings.TrimSpace(doc.Text[p-1])
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if p == 1 && utf8.RuneCountInString(part) > pagesBudget {
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parts = append(parts, truncateRunes(part, pagesBudget))
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return pagesResult{text: strings.Join(parts, "\n\n"), last: 1}
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}
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if running+utf8.RuneCountInString(part) > pagesBudget {
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break
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}
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running += utf8.RuneCountInString(part)
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parts = append(parts, part)
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last = p
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}
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return pagesResult{text: strings.Join(parts, "\n\n"), last: last}
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}
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// renderPages renders a page range as whole pages, capped at maxPages pages and
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// at OutCap runes, noting how to ask for the rest.
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func renderPages(doc *pdftext.Doc, opt Options) (Rendered, error) {
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start, end, err := parsePages(opt.Pages, len(doc.Text))
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if err != nil {
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return Rendered{}, err
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}
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limit := end
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if end-start+1 > maxPages {
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limit = start + maxPages - 1
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}
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var parts []string
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running := 0
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last := start - 1
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note := ""
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for p := start; p <= limit; p++ {
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part := Marker(p) + "\n\n" + strings.TrimSpace(doc.Text[p-1])
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if p == start && utf8.RuneCountInString(part) > opt.OutCap {
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parts = append(parts, truncateRunes(part, opt.OutCap))
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note = fmt.Sprintf("page %d cut to fit the answer", p)
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last = p
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break
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}
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if running+utf8.RuneCountInString(part) > opt.OutCap {
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break
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}
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running += utf8.RuneCountInString(part)
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parts = append(parts, part)
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last = p
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}
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if last < end {
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note = fmt.Sprintf("cut at page %d; ask for pages=\"%d-%d\"", last, last+1, end)
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}
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return Rendered{Content: strings.Join(parts, "\n\n"), First: start, Last: last, Note: note}, nil
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}
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// parsePages parses a "a-b", "a" or "a-" spec against the number of extracted
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// pages. It returns a range error wrapping ErrBadPages when the numbers are out
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// of range, and a format error wrapping ErrBadPages otherwise.
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func parsePages(spec string, extracted int) (start, end int, err error) {
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s := strings.TrimSpace(spec)
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start, end, endToExtracted, ok := splitSpec(s)
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if !ok {
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return 0, 0, fmt.Errorf("%w: invalid pages", ErrBadPages)
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}
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if endToExtracted {
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end = extracted
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}
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if start < 1 || end < start || start > extracted {
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return 0, 0, fmt.Errorf("%w: pages out of range (1-%d)", ErrBadPages, extracted)
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}
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if end > extracted {
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end = extracted
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}
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return start, end, nil
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}
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// splitSpec turns a spec into its numbers. It reports ok=false for a malformed
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// spec so the caller returns a format error. A bare "a" is a single page; "a-"
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// spans to the last extracted page.
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func splitSpec(s string) (start, end int, endToExtracted, ok bool) {
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if !strings.Contains(s, "-") {
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n, err := strconv.Atoi(s)
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if err != nil {
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return 0, 0, false, false
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}
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return n, n, false, true
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}
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parts := strings.Split(s, "-")
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if len(parts) != 2 || parts[0] == "" {
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return 0, 0, false, false
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}
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a, err := strconv.Atoi(strings.TrimSpace(parts[0]))
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if err != nil {
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return 0, 0, false, false
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}
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if strings.TrimSpace(parts[1]) == "" {
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return a, 0, true, true
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}
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b, err := strconv.Atoi(strings.TrimSpace(parts[1]))
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if err != nil {
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return 0, 0, false, false
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}
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return a, b, false, true
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}
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// truncateRunes returns the first n runes of s, never splitting a multi-byte one.
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func truncateRunes(s string, n int) string {
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if n <= 0 {
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return ""
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}
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if utf8.RuneCountInString(s) <= n {
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return s
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}
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return string([]rune(s)[:n])
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}
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