// framed.typ — artwork inset inside a generous coloured frame.
//
// The gallery layout, and the safest of the five: the type NEVER sits on the artwork,
// so a busy, high-variance image can never eat a word of it. The coloured frame is the
// page itself (`palette.bg`), the artwork is a panel floated inside it, and every text
// block lives in the frame's margins.
//
// Two compositions, chosen from the trim's aspect ratio — never one layout scaled:
//
//   STACKED (portrait and square-ish: a3, a4, ig-post, ig-story)
//     +----------------------+   art panel across the top, flush with the side frames,
//     |    +------------+    |   the type band in the deeper bottom margin. The classic
//     |    |    art     |    |   museum poster. The band takes only what the type needs,
//     |    +------------+    |   so every spare millimetre goes back to the picture.
//     |  TITOLO              |
//     |  data · luogo        |
//     +----------------------+
//
//   SIDE (landscape: fb-cover, yt-thumb)
//     +---------------------------+  a 2.5:1 cover has no room for a bottom band — it
//     | TITOLO  |     art         |  would be a 12 mm strip. So the frame margin that
//     | data    |                 |  carries the type moves to the left edge and becomes
//     +---------------------------+  a column; the artwork fills the rest.
//
// Everything is drawn in `page(background:)`, whose origin is the FULL page INCLUDING
// bleed — hence the `+ b` on every coordinate. One coordinate system for the whole
// composition is the only reliable defence against the classic bleed bug. Only the frame
// colour bleeds; the art panel is inset by definition and never reaches the trim, which
// is what makes this template unusually forgiving to print.

#import "lib.typ": *
#let spec = json(sys.inputs.specfile)

// ---------------------------------------------------------------------------
// Tunables — fractions of the trim's SHORT edge or of the trim itself, so the piece
// looks the same at 1080 px and at 300 dpi A3.
// ---------------------------------------------------------------------------

/// Frame width: the margin between the trim and the art panel. Generous on purpose —
/// a mean frame reads as a printing mistake, a wide one reads as a decision.
#let FRAME-RATIO = 0.070

/// Breathing space between the panel and the type, and between type blocks.
#let GAP-RATIO = 0.030

/// The type band may never take more than `BAND-MAX` of the height (stacked), and the
/// picture may never be squeezed below `ART-MIN`. Between them they keep the piece a
/// framed picture with a caption, rather than a caption with a stamp.
#let BAND-MAX = 0.50
#let ART-MIN = 0.28

/// Width of the type column in the landscape composition, as a fraction of the width
/// inside the frame. Wide enough for a readable measure, narrow enough to leave a picture.
#let COL-RATIO = 0.40

/// Hairline keyline around the art panel — a gallery frame's inner edge. Scales with the
/// piece so it stays a hairline instead of becoming a rule.
#let KEYLINE-RATIO = 0.0016

/// Ceiling on the lines each role may claim while the band is budgeted. The auto-fit is
/// what actually guarantees the text fits; this only stops one very long block from
/// claiming the whole band before the others have been placed.
#let MAX-LINES = (title: 4, subtitle: 3, date: 2, venue: 2, details: 4, price: 2, footer: 2)

/// Rough line box (cap height plus leading), used only for the cap above.
#let LINE-FACTOR = 1.34

/// How far the stack may be squeezed before an optional block is dropped instead. Losing
/// 10% of the type is cheaper than losing the price of a ticket.
#let SQUEEZE-ALLOWANCE = 0.12

/// Floors for the staged squeeze: gaps give up half their air before the supporting type
/// is touched, and the supporting type gives up 30% before the headline is touched.
#let GAP-FLOOR = 0.45
#let MINOR-FLOOR = 0.70

/// Width of the coloured frame: the margin between the trim and everything inside it.
/// Never narrower than the safe margin, never so wide that it eats the picture — 18% of
/// the short edge per side is already a very deep mount. The logo is aligned to this
/// same edge, which is why it is a function rather than a local.
#let frame-of(spec) = {
  let sa = safe-area(spec)
  calc.min(calc.max(sa.safe, sa.short-edge * FRAME-RATIO), sa.short-edge * 0.18)
}

// ---------------------------------------------------------------------------
// Blocks
// ---------------------------------------------------------------------------

/// Every renderable block in SPEC ORDER, with its resolved style and its text already
/// uppercased where the role calls for it. Blocks that are not dictionaries, or whose
/// text is missing or blank, simply do not exist — a half-filled spec must still print.
#let entries(spec) = {
  let bs = _get(spec, "blocks", ())
  if type(bs) != array { return () }
  let out = ()
  for b in bs {
    if type(b) != dictionary { continue }
    let raw = _get(b, "text", "")
    if type(raw) != str or raw.trim() == "" { continue }
    let st = block-style(spec, _get(b, "role", none), surface: "bg")
    out.push((
      st: st,
      body: if st.upper { upper(raw) } else { raw },
      // Only an explicit `true` makes a block droppable; anything else is mandatory.
      optional: _get(b, "optional", false) == true,
    ))
  }
  out
}

// ---------------------------------------------------------------------------
// The unbreakable-word cap
// ---------------------------------------------------------------------------
//
// ⚠️ Why this exists. `fit` accepts a candidate when `measure(width: w, ...)` reports a
// width within `w` — but Typst CLAMPS the reported width of an overfull paragraph to the
// region it was measured in. A single word too wide to break (`DELL'AUTUNNO` at 47 pt in
// a 75 mm column) therefore measures as fitting, and then draws straight across the
// artwork. Measured: word 380.5 pt, column 212.3 pt, `measure().width` = 212.3 pt.
//
// Typst cannot hyphenate its way out either: `hyphenate: auto` only applies with
// justification, and posters are set ragged. So the size has to be capped BEFORE the fit,
// from the width of the longest word — which is exact, since advance width is linear in
// size.

/// Widest single word of `body` at `size`/`wd`, as an absolute length.
#let widest-word(st, size, wd, words) = {
  let widest = 0pt
  for word in words {
    let m = measure(text(.._text-args(st.family, size, st.weight, st.tracking, none, wd), word))
    widest = calc.max(widest, m.width)
  }
  widest
}

/// Largest size — and the widest `wdth` instance — at which every word of `body` fits in
/// `w`. Returns `(size, wdth)`, where `wdth` is handed to `fit` as `natural-wdth`, i.e.
/// as a CEILING: the fit may still narrow further, it may never go wider than this.
///
/// Narrowing is spent before size: a condensed headline in a narrow column is a
/// typographic decision, a small one is a defeat.
#let word-cap(st, body, w) = {
  let words = body.split(regex("\\s+")).filter(x => x.trim() != "")
  if words.len() == 0 { return (size: st.size, wdth: 100) }

  let rng = _axis-range(st.axes.at("wdth", default: none))
  // `fit` never goes past the family's natural instance, so 100 is the real ceiling.
  let hi = if rng == none { none } else { calc.min(calc.max(rng.at(0), rng.at(1)), 100) }
  let lo = if rng == none { none } else { calc.min(rng.at(0), rng.at(1)) }

  if widest-word(st, st.size, hi, words) <= w { return (size: st.size, wdth: 100) }

  if rng != none and lo < hi {
    let narrow = widest-word(st, st.size, lo, words)
    if narrow <= w {
      // The axis alone can save it: find the widest instance that still fits. Bisection
      // rather than interpolation because `avar` makes the axis non-linear.
      let a = lo
      let z = hi
      let i = 0
      while i < 8 {
        let mid = (a + z) / 2
        if widest-word(st, st.size, mid, words) <= w { a = mid } else { z = mid }
        i += 1
      }
      return (size: st.size, wdth: a)
    }
    // Axis exhausted: stay at the narrow end and pay the rest in size.
    return (size: st.size * (w / narrow) * 0.99, wdth: lo)
  }

  // No axis to spend: scale the size down by exactly the overflow.
  let plain = widest-word(st, st.size, hi, words)
  (size: st.size * (w / plain) * 0.99, wdth: 100)
}

/// A block resolved against a specific column width: its capped size, the `wdth` ceiling
/// and the argument dictionary to spread into `fit`.
///
/// Must be called from a `context` block: it measures.
#let tune(it, w) = {
  let cap = word-cap(it.st, it.body, w)
  let k = cap.size / it.st.size
  let args = it.st.args
  args.size = cap.size
  args.min-size = it.st.min-size * k
  (
    st: it.st,
    body: it.body,
    optional: it.optional,
    wdth: cap.wdth,
    args: args,
    // Height it takes at its capped size and at the NARROWEST width the fit may use —
    // the best case `fit` can reach without shrinking. Budgeting against the best case is
    // what lets a long Italian title keep its size by narrowing instead of being handed
    // three lines' worth of room and dutifully filling them.
    wants: {
      let rng = _axis-range(it.st.axes.at("wdth", default: none))
      let wd = if rng == none { none } else {
        calc.min(calc.min(rng.at(0), rng.at(1)), cap.wdth)
      }
      let h = measure(width: w, {
        set par(leading: it.st.leading, linebreaks: "optimized", justify: false)
        text(.._text-args(it.st.family, cap.size, it.st.weight, it.st.tracking, none, wd), it.body)
      }).height
      calc.min(h, MAX-LINES.at(it.st.role, default: 2) * cap.size * LINE-FACTOR)
    },
  )
}

// ---------------------------------------------------------------------------
// Budgeting the stack
// ---------------------------------------------------------------------------

/// Space above block `i`. A title is followed by a wider gap: the reader needs to see
/// where the headline stops and the practical information starts.
#let gap-before(items, i, gap) = {
  if i == 0 { return 0pt }
  if items.at(i - 1).st.role == "title" { gap * 1.7 } else { gap }
}

/// Take `deficit` out of `values`, but never below `floor` of their own size.
/// Returns `(values, remaining-deficit)`.
#let take-from(values, deficit, floor) = {
  let sum = values.sum(default: 0pt)
  if sum <= 0pt or deficit <= 0pt { return (values, deficit) }
  let take = calc.min(deficit, sum * (1 - floor))
  let k = (sum - take) / sum
  (values.map(v => v * k), deficit - take)
}

/// Budget the type stack into `max-h`.
///
///   1. Measure what every block wants (word-capped, best-case width).
///   2. While the stack cannot be squeezed into the band, drop the LAST `optional: true`
///      block — the spec orders blocks by priority, so the last optional one is the least
///      missed. A block is never dropped for a shortfall a mild squeeze can absorb.
///   3. Squeeze in stages: air first, then the supporting blocks, and only then the
///      headline. A poster survives tight leading; it does not survive a small title.
///
/// Whatever `fit` is finally handed, it enforces — this only decides who pays.
#let budget(items, w, gap, max-h) = {
  let plan(list) = {
    let tuned = list.map(it => tune(it, w))
    let hs = tuned.map(it => it.wants)
    let gs = range(tuned.len()).map(i => gap-before(tuned, i, gap))
    (tuned, hs, gs, hs.sum(default: 0pt) + gs.sum(default: 0pt))
  }

  let (tuned, hs, gs, total) = plan(items)

  // Drop optional blocks, last first, while even a full squeeze would not be enough.
  while total > max-h * (1 + SQUEEZE-ALLOWANCE) {
    let drop = none
    for i in range(tuned.len()) {
      if tuned.at(i).optional { drop = i }
    }
    if drop == none { break }
    let kept = tuned.slice(0, drop) + tuned.slice(drop + 1)
    let (t2, h2, g2, tot2) = plan(kept)
    tuned = t2
    hs = h2
    gs = g2
    total = tot2
  }

  if total > max-h {
    let deficit = total - max-h

    // 1. The air between blocks.
    let (gs2, d1) = take-from(gs, deficit, GAP-FLOOR)
    gs = gs2

    // 2. Everything that is not the headline.
    let d2 = d1
    if d2 > 0pt {
      let minor = range(hs.len()).filter(i => tuned.at(i).st.role != "title")
      let vals = minor.map(i => hs.at(i))
      let (vals2, rest) = take-from(vals, d2, MINOR-FLOOR)
      for (n, i) in minor.enumerate() { hs.at(i) = vals2.at(n) }
      d2 = rest
    }

    // 3. Last resort: everything, uniformly. `fit` shrinks the type into it.
    if d2 > 0pt {
      let (hs2, _) = take-from(hs, d2, 0)
      hs = hs2
    }
  }

  (items: tuned, heights: hs, gaps: gs, height: hs.sum(default: 0pt) + gs.sum(default: 0pt))
}

/// Draw a budgeted stack from `(x, y)`, top-anchored, in a `w`-wide column.
#let draw-stack(plan, x, y, w, align-to) = {
  let cy = y
  for i in range(plan.items.len()) {
    let it = plan.items.at(i)
    cy += plan.gaps.at(i)
    place(
      top + left,
      dx: x,
      dy: cy,
      block(
        width: w,
        fit(
          it.body, w, plan.heights.at(i),
          it.st.family, it.st.axes,
          align-to: align-to,
          natural-wdth: it.wdth,
          ..it.args,
        ),
      ),
    )
    cy += plan.heights.at(i)
  }
}

// ---------------------------------------------------------------------------
// Art panel
// ---------------------------------------------------------------------------

/// The inset artwork, its keyline, and — only when the renderer measured the art as busy
/// — a soft scrim along the edge that faces the type.
///
/// `fit: "cover"` in a fixed-size, clipped block: the artwork fills the panel at its own
/// aspect ratio and the overflow is cropped, so a 4:5 generation is never distorted to
/// fill a 2.5:1 cover panel.
///
/// The scrim here is NOT a legibility fix — no text ever crosses this panel. It is a
/// vignette that settles a noisy image into the frame colour instead of letting it butt
/// against it, which is exactly the case (`needs_scrim`) the renderer flags.
#let art-panel(spec, pal, w, h, short, scrim-edge) = {
  let path = _get(spec, "art_file", none)
  let has-art = type(path) == str and path.trim() != ""
  let keyline = calc.max(0.2pt, short * KEYLINE-RATIO)

  block(
    width: w,
    height: h,
    clip: true,
    // The keyline sits on the panel edge, in ink at low strength: it defines the picture
    // without competing with it. Over a dark frame it reads light and over a light frame
    // dark, because `ink` is already the contrast-checked colour for this background.
    stroke: keyline + pal.ink.transparentize(72%),
    // No artwork yet (a text-only draft): a flat tint keeps the composition honest
    // instead of leaving a hole where the picture goes.
    fill: if has-art { none } else { pal.ink.transparentize(88%) },
    {
      if has-art {
        image(path, width: 100%, height: 100%, fit: "cover")
      }
      if _get(spec, "needs_scrim", false) == true and scrim-edge != none {
        if scrim-edge == "bottom" {
          // Solid at the panel's bottom edge, fading up into the picture.
          place(bottom + left, scrim(h * 0.34, pal.scrim, 90deg, width: 100%, strength: 62%))
        } else {
          // Landscape: solid at the left edge, fading right — away from the type column.
          place(top + left, scrim(h, pal.scrim, 180deg, width: w * 0.30, strength: 62%))
        }
      }
    },
  )
}

// ---------------------------------------------------------------------------
// Logo reserve
// ---------------------------------------------------------------------------

/// `logo-place` anchors the logo at the safe corner, which in this template is inside the
/// frame margin — the right place for it. But the frame is only ~7% of the short edge and
/// a logo may be up to 40%, so the layout has to be told to keep out of its corner.
///
/// Returns the reserve as a length (`0pt` when there is no logo) plus its corner. The
/// reserve is a SQUARE of the logo's width, because `logo-place` constrains width only:
/// a taller-than-wide logo can still exceed it, which costs a little artwork and never a
/// word of type.
#let logo-reserve(spec, short) = {
  let logo = _get(spec, "logo", none)
  if type(logo) != dictionary { return (size: 0pt, corner: none) }
  let path = _get(logo, "path", none)
  if type(path) != str or path.trim() == "" { return (size: 0pt, corner: none) }
  let raw = _get(logo, "scale", 0.12)
  let s = if type(raw) in (int, float) { calc.max(0.02, calc.min(0.4, raw)) } else { 0.12 }
  let corner = _get(logo, "corner", "br")
  (
    size: short * s,
    corner: if corner in ("tl", "tr", "bl", "br") { corner } else { "br" },
  )
}

// ---------------------------------------------------------------------------
// Composition
// ---------------------------------------------------------------------------

#let compose(spec) = context {
  let pal = palette-of(spec, surface: "bg")
  let sa = safe-area(spec)
  let short = sa.short-edge
  let b = sa.bleed
  let tw = sa.trim-width
  let th = sa.trim-height

  let frame = frame-of(spec)
  let gap = short * GAP-RATIO
  let lg = logo-reserve(spec, short)
  let items = entries(spec)

  // Landscape gets the side composition. The threshold sits above 1 on purpose: a
  // 1080x1350 ig-post is "wide" only arithmetically and reads as a portrait.
  let landscape = (tw / th) >= 1.2

  if landscape {
    // ---- SIDE: type column left, art right -------------------------------------
    let inner-w = tw - 2 * frame
    let col-w = inner-w * COL-RATIO
    let art-x = frame + col-w + gap
    let art-w = tw - frame - art-x
    let art-y = frame
    let art-h = th - 2 * frame

    // A logo on the right would sit on the artwork: give it a full-height gutter instead.
    // Landscape art is wide and shallow, so width is the cheap axis here.
    if lg.corner in ("tr", "br") and lg.size > 0pt {
      art-w = calc.max(inner-w * 0.30, art-w - lg.size - gap)
    }

    // A logo on the left sits in the type column: shorten the column at that end.
    let col-y = art-y
    let col-h = art-h
    if lg.corner == "tl" and lg.size > 0pt {
      col-y += lg.size + gap * 0.6
      col-h -= lg.size + gap * 0.6
    } else if lg.corner == "bl" and lg.size > 0pt {
      col-h -= lg.size + gap * 0.6
    }

    let plan = budget(items, col-w, gap, calc.max(0pt, col-h))
    // Optically centre the stack in the column: a top-anchored column beside a full-height
    // picture reads as if the type has slipped.
    let sy = col-y + calc.max(0pt, (col-h - plan.height) / 2)

    place(top + left, dx: b + art-x, dy: b + art-y,
      art-panel(spec, pal, art-w, art-h, short, "left"))
    draw-stack(plan, b + frame, b + sy, col-w, left)
  } else {
    // ---- STACKED: art on top, type band in the bottom margin --------------------
    // A logo in a top corner would land on the picture, so the top frame grows to clear
    // it; in a bottom corner it gets its own strip beneath the type band, which is how
    // civic posters carry their patron's mark anyway.
    let clearance = lg.size + gap * 0.6
    let top-extra = if lg.corner in ("tl", "tr") { clearance } else { 0pt }
    let bottom-extra = if lg.corner in ("bl", "br") { clearance } else { 0pt }

    let art-x = frame
    let art-y = frame + top-extra
    let art-w = tw - 2 * frame
    let band-bottom = th - frame - bottom-extra

    // The band gets what it asks for, capped so the picture keeps its floor. What it does
    // not use goes to the artwork rather than to slack: a short title means a big picture.
    let room = band-bottom - art-y - gap - th * ART-MIN
    let max-band = calc.max(th * 0.12, calc.min(th * BAND-MAX, room))
    let plan = budget(items, art-w, gap, max-band)

    let band-y = band-bottom - plan.height
    let art-h = calc.max(th * 0.12, band-y - gap - art-y)

    place(top + left, dx: b + art-x, dy: b + art-y,
      art-panel(spec, pal, art-w, art-h, short, "bottom"))
    draw-stack(plan, b + art-x, b + band-y, art-w, left)
  }
}

// ---------------------------------------------------------------------------
// Page
// ---------------------------------------------------------------------------

#let pal = palette-of(spec, surface: "bg")
#let sa = safe-area(spec)

// `date: none` is the load-bearing line for byte-identical output — without it the PDF
// carries a creation timestamp and every golden-file test becomes a coin toss.
#set document(date: none)
#set text(lang: "it", fill: pal.ink)
#set par(linebreaks: "optimized")

#set page(
  width: sa.trim-width,
  height: sa.trim-height,
  margin: 0pt,
  bleed: sa.bleed,
  // The frame colour IS the page, so it covers the bleed too and the guillotine can land
  // anywhere in those 3 mm without exposing white.
  fill: pal.bg,
  background: compose(spec),
  foreground: {
    // Aligned to the frame's inner edge, not to the safe corner: the logo then shares a
    // margin with the picture and the type instead of hanging out towards the trim. The
    // composition reserves exactly this much room for it.
    logo-place(spec, margin: sa.bleed + frame-of(spec))
    crop-marks(spec)
  },
)

// The composition lives entirely in `background:`/`foreground:`, which resolve against the
// full bleed page. The body only has to exist so that Typst emits the page.
#v(0pt)