// cph-render — curriculum lesson render package.
//
// PUBLIC ENTRY: `render-lesson(info, target, parts, heading-numbering)`.
//
// MODEL (ADR-0011). A build compiles a *template file* (e.g. `exports/student.typ`)
// as the typst main, with the manifest injected via `--input manifest=<path>`.
// The template reads the manifest, loads each part's content, and calls
// `render-lesson` here. Presentation (heading numbering) lives in the template,
// not the manifest, not hardcoded-unreachable in this package — we only provide
// the DEFAULT scheme (`default-heading-numbering`) for the template to use or
// override.
//
// WHY THE TEMPLATE LOADS CONTENT, NOT US (the include-resolution finding):
//   typst resolves an `include`/`import` path relative to THE PACKAGE/FILE THE
//   include LEXICALLY APPEARS IN, and a package (`@local/cph-render`) has its OWN
//   virtual root. A dynamic `include` written inside this file resolves against
//   the PACKAGE root — even an absolute `/segments/x.typ` lands in the package
//   dir, NOT the engineering-file root (`--root`). Verified empirically.
//   Therefore the dynamic-include LOOP must live in the TEMPLATE (which lives at
//   `<root>/exports/*.typ`, so `/<part.path>/<field>.typ` resolves against
//   `--root`). `render-lesson` is content-in: it takes an ALREADY-ASSEMBLED
//   `parts` array of dicts and never includes anything itself.
//
// A part dict the template hands us:
//   `kind` plus that kind's content/scalar fields. Content field VALUES are
//   already-evaluated typst content (the template produced them via `include`).
//
// kind -> fields (MVP) — see `part-fields` below, which the template uses to
// know what to load:
//   segment : textbook (content, required)
//   example : problem (content, required), solution (content, required),
//             source (string scalar, optional, from <path>/element.toml)
//   lemma   : stmt (content, required), proof (content, optional)
//   sop     : sop (content, required)
//
// target -> show/hide (the (kind x target) render matrix; defaults per
// ADR-0005/0008, derived internally — template passes only the target string):
//   student : example problem only (hide solution); lemma stmt only (hide
//             proof); segment textbook; sop shown.
//   teacher : everything shown.
//   unknown : rendered conservatively == student (show only required-public
//             fields). Never crashes. The "no render rule => warning"
//             diagnostic is the Rust side's job, not ours.

#import "src/style.typ": base-style, default-heading-numbering, title-block, subtitle-block
#import "src/elements/segment.typ": display-segment
#import "src/elements/example.typ": display-example
#import "src/elements/lemma.typ": display-lemma
#import "src/elements/sop.typ": display-sop
#import "src/elements/common.typ": example-counter, lemma-counter

/// Per-kind field manifest, exported so a TEMPLATE knows exactly what to load
/// for each part without hardcoding the matrix. For each kind:
///   `content`: field names whose `<part.path>/<field>.typ` the template must
///              `include` (assembling them into the part dict).
///   `optional-content`: content fields that may be absent (template should
///              probe before including; absence is fine).
///   `scalars`: scalar field names the template reads from `<path>/element.toml`
///              (currently only example `source`).
/// Keeping this here (not in the template) keeps kind->fields a single source of
/// truth in the package; the template iterates it generically.
#let part-fields = (
  segment: (content: ("textbook",), optional-content: (), scalars: ()),
  example: (content: ("problem", "solution"), optional-content: (), scalars: ("source",)),
  lemma: (content: ("stmt",), optional-content: ("proof",), scalars: ()),
  sop: (content: ("sop",), optional-content: (), scalars: ()),
)

/// Resolve a target string to the set of show/hide booleans.
/// Unknown targets fall back to the conservative (student-like) profile.
#let _flags-for(target) = {
  if target == "teacher" {
    (show-solution: true, show-proof: true, subtitle: [教师版讲义])
  } else if target == "student" {
    (show-solution: false, show-proof: false, subtitle: [学生版讲义])
  } else {
    // Unknown target: conservative — show only required-public fields.
    (show-solution: false, show-proof: false, subtitle: [讲义])
  }
}

/// Render one part according to its `kind`. Unknown kinds render an inline
/// note instead of crashing.
#let _render-part(part, flags) = {
  let kind = part.at("kind", default: none)
  if kind == "segment" {
    display-segment(part)
  } else if kind == "example" {
    display-example(part, show-solution: flags.show-solution)
  } else if kind == "lemma" {
    display-lemma(part, show-proof: flags.show-proof)
  } else if kind == "sop" {
    display-sop(part)
  } else {
    // Don't crash on an unrecognised kind; surface it visibly instead.
    block(
      width: 100%,
      inset: 0.6em,
      fill: red.lighten(85%),
      stroke: red.darken(20%) + 0.6pt,
      radius: 0.4em,
      text(fill: red.darken(30%), weight: "bold")[
        [未知部件类型 / unknown kind: #repr(kind)]
      ],
    )
  }
}

/// THE ENTRY POINT — called by a template (`exports/*.typ`).
///
/// - `info`:   dict, e.g. (title: "…", author: "…"). `author` may be absent.
///             Templates typically pass `manifest.at("info", default: (:))`.
/// - `target`: string. MVP: "student" | "teacher". Unknown => conservative.
///             Each template hardcodes its own target (student.typ => "student").
/// - `parts`:  ordered array of part dicts, ALREADY ASSEMBLED by the template
///             (content fields included, scalars read). See file header.
/// - `heading-numbering`: array of per-level numbly pattern strings, e.g.
///             `("{1:一}、", "{1:1}.{2:1}", "{1:1}.{2:1}.{3:1}")`. Presentation
///             lives in the template (ADR-0011); the template passes its chosen
///             scheme. Defaults to `default-heading-numbering` (the framework
///             default) when the template omits it.
#let render-lesson(
  info: (:),
  target: "student",
  parts: (),
  heading-numbering: default-heading-numbering,
) = {
  let title = info.at("title", default: [])
  let author = info.at("author", default: none)

  // `document` author wants a string/array; normalise the optional field.
  set document(
    title: title,
    author: if author == none { () } else { author },
  )

  show: base-style.with(heading-numbering: heading-numbering)

  // Reset shared counters so each rendered lesson numbers from 1.
  example-counter.update(0)
  lemma-counter.update(0)

  let flags = _flags-for(target)

  title-block()
  subtitle-block(flags.subtitle)

  // Render strictly in array order.
  for part in parts {
    _render-part(part, flags)
  }
}
