// example: a worked example / problem.
//
// Contract fields:
//   content: `problem` (required), `solution` (required)
//   scalar:  `source` (optional string)
//
// Numbered "例题 N" via the shared example-counter.
//   student: show `problem`, HIDE `solution`.
//   teacher: show both.
// `source`, when present, is shown as a small annotation on the problem line.

#import "../fonts.typ"
#import "common.typ": element-box, tag-line, divider, example-counter, hue-of

#let display-example(part, show-solution: true) = {
  let theme = oklch(70%, 0.08, hue-of.example * 1deg)
  example-counter.step()

  element-box(hue-of.example, {
    // Problem
    tag-line(context [例题 #example-counter.display()])
    let source = part.at("source", default: none)
    if source != none and source != "" {
      text(size: 0.85em, fill: gray.darken(30%))[（来源：#source）]
      h(0.3em)
    }
    set text(font: fonts.accent)
    part.problem

    // Solution (teacher-only by default)
    if show-solution {
      divider(theme)
      tag-line[解析]
      set text(font: fonts.accent)
      part.solution
    }
  })
}