;; Compute all positioned lines for a paragraph.
(defcomp
  ()
  (let
    ((sample-words (split "In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by him; and without him was not any thing made that was made. In him was life; and the life was the light of men." " "))
      (font "serif")
      (size 15))
    (let
      ((sw (list)) (n-words (len sample-words)))
      (for-each
        (fn
          (w)
          (let
            ((m (measure-text font size w)))
            (append! sw (get m :width))))
        sample-words)
      (let
        ((space-m (measure-text font size " "))
          (space-w (get (measure-text font size " ") :width)))
        (div
          (begin
            (~tw :tokens "space-y-10")
            (~font
              :family "Pretext Serif"
              :src "/static/fonts/DejaVuSerif.ttf"))
          (div
            (~tw :tokens "space-y-4")
            (div
              (h1
                (~tw
                  :tokens "text-3xl font-bold text-stone-900 tracking-tight")
                "Pretext")
              (p
                (~tw :tokens "mt-1 text-lg text-stone-500")
                "DOM-free text layout. One IO boundary. Pure arithmetic."))
            (let
              ((hero-max 520) (hero-ranges (break-lines sw space-w 520)))
              (div
                (~tw :tokens "max-w-xl mx-auto mt-6")
                (~pretext-demo/render-paragraph
                  :lines (pretext-layout-lines
                    sample-words
                    sw
                    hero-ranges
                    space-w
                    hero-max
                    24)
                  :max-width hero-max
                  :n-words n-words
                  :label "Knuth-Plass optimal line breaking — John 1:1–4"))))
          (div
            (~tw
              :tokens "rounded-lg border border-violet-200 bg-violet-50 p-5")
            (p
              (~tw :tokens "text-sm text-violet-800")
              (strong "One ")
              (code (~tw :tokens "bg-violet-100 px-1 rounded") "perform")
              " for glyph measurement. Everything else — line breaking, positioning, hyphenation, justification — is pure SX functions over numbers. "
              "Server renders with font-table lookups. Browser uses "
              (code "canvas.measureText")
              ". Same algorithm, same output."))
          (div
            (~tw :tokens "space-y-3")
            (h2
              (~tw :tokens "text-xl font-semibold text-stone-800")
              "Greedy vs optimal")
            (p
              (~tw :tokens "text-sm text-stone-500")
              "Most web text uses greedy word wrap — break when the next word doesn't fit. "
              "Knuth-Plass considers all possible breaks simultaneously, minimizing total raggedness.")
            (let
              ((nm 340))
              (div
                (~tw :tokens "grid grid-cols-1 md:grid-cols-2 gap-4")
                (~pretext-demo/render-paragraph
                  :lines (pretext-layout-lines
                    sample-words
                    sw
                    (break-lines-greedy sw space-w nm)
                    space-w
                    nm
                    22)
                  :max-width nm
                  :line-height 22
                  :n-words n-words
                  :label "Greedy (browser default)")
                (~pretext-demo/render-paragraph
                  :lines (pretext-layout-lines
                    sample-words
                    sw
                    (break-lines sw space-w nm)
                    space-w
                    nm
                    22)
                  :max-width nm
                  :line-height 22
                  :n-words n-words
                  :label "Knuth-Plass optimal"))))
          (div
            (~tw :tokens "space-y-3")
            (h2
              (~tw :tokens "text-xl font-semibold text-stone-800")
              "How lines are scored")
            (p
              (~tw :tokens "text-sm text-stone-500")
              "Each line gets a badness score — how far it deviates from ideal width. "
              "The algorithm minimizes total demerits (1 + badness)² across all lines.")
            (div
              (~tw :tokens "grid grid-cols-4 md:grid-cols-8 gap-2")
              (map
                (fn
                  (used)
                  (let
                    ((bad (line-badness used 100))
                      (pct (str (min used 100) "%")))
                    (div
                      (~tw
                        :tokens "rounded border border-stone-200 p-2 text-center")
                      (div
                        :style (str
                          "height:4px;background:linear-gradient(90deg,hsl(263,70%,50%) "
                          pct
                          ",#e7e5e4 "
                          pct
                          ");border-radius:2px;margin-bottom:6px;")
                        "")
                      (div
                        (~tw :tokens "text-sm font-mono font-bold")
                        (if
                          (>= bad 100000)
                          (span (~tw :tokens "text-red-500") "∞")
                          (span (~tw :tokens "text-stone-700") (str bad))))
                      (div
                        (~tw :tokens "text-xs text-stone-400 mt-0.5")
                        (str used "%")))))
                (list 100 95 90 85 80 70 50 110))))
          (div
            (~tw :tokens "space-y-3")
            (h2
              (~tw :tokens "text-xl font-semibold text-stone-800")
              "Hyphenation")
            (p
              (~tw :tokens "text-sm text-stone-500")
              "Liang's algorithm: a trie of character patterns with numeric levels. "
              "Odd levels mark valid break points.")
            (let
              ((trie (make-hyphenation-trie (list "hy1p" "he2n" "hen3at" "hena4t" "1na" "n2at" "1tio" "2io" "o2i" "1tic" "1mo" "4m1p" "1pu" "put1" "1er" "pro1g" "1gram" "2gra" "program5" "pro3" "ty1" "1graph" "2ph"))))
              (div
                (~tw :tokens "flex flex-wrap gap-3")
                (map
                  (fn
                    (word)
                    (let
                      ((syllables (hyphenate-word trie word)))
                      (div
                        (~tw
                          :tokens "rounded-lg border border-stone-200 bg-white px-4 py-3 text-center")
                        (div
                          (~tw
                            :tokens "text-lg font-mono font-semibold text-stone-800 tracking-wide")
                          (map-indexed
                            (fn
                              (i syl)
                              (if
                                (= i 0)
                                (span syl)
                                (<>
                                  (span :class "text-violet-400 mx-0.5" "·")
                                  (span syl))))
                            syllables))
                        (div (~tw :tokens "text-xs text-stone-400 mt-1") word))))
                  (list "hyphen" "computation" "programming" "typography")))))
          (div
            (~tw
              :tokens "rounded-lg border border-stone-200 bg-stone-50 p-5 space-y-2")
            (h3
              (~tw
                :tokens "text-sm font-semibold text-stone-600 uppercase tracking-wide")
              "The pipeline")
            (ol
              (~tw
                :tokens "list-decimal list-inside text-sm text-stone-600 space-y-1")
              (li
                (code "measure-text")
                " — the only IO. Server: font tables. Browser: "
                (code "canvas.measureText"))
              (li
                (code "break-lines")
                " — Knuth-Plass DP over word widths → optimal break points")
              (li
                (code "position-lines")
                " — pure arithmetic: widths + breaks → x,y coordinates")
              (li
                (code "hyphenate-word")
                " — Liang's trie: character patterns → syllable boundaries")
              (li
                "All layout is "
                (strong "deterministic")
                " — same widths → same positions, every time")))
          (div
            (~tw :tokens "space-y-3")
            (h2
              (~tw :tokens "text-xl font-semibold text-stone-800")
              "Live layout (client-side)")
            (p
              (~tw :tokens "text-sm text-stone-500")
              "Same algorithm running in the browser. "
              (code "canvas.measureText")
              " gives pixel-perfect metrics — the browser that measures is the browser that renders. "
              "Drag the sliders to re-layout in real time.")
            (div :data-sx-island "pretext-demo/live" "")))))))
