#let cnfont = ("Noto Sans CJK SC", "Noto Sans SC", "Source Han Sans CN")
#let cnmainfont = ("Noto Serif CJK SC", "Source Han Serif CN")

#let mtext(body) = text(font: cnmainfont, weight: "regular", body)

#let tab = h(2em)
#let halftab = h(1em)

#let footer_title = state("footer_title", "")
#let skip_footer = state("skip_footer", false)

#let thispage_number(loc) = {
	let numberstarter = query(<PageNumberingStated>, before: loc)
	if numberstarter == () {
		none
	} else {
		loc.page() - numberstarter.first().location().page() + 1
	}
}

#let problem_id = counter("pid")

#let project(title: "", logo: none, body) = {
	set document(title: title)
	set text(font: cnmainfont, lang: "zh")
	set page(
		width: 195mm,
		height: 270mm,
		margin: (top: 20mm)
	)

	show par: set block(above: 1.2em, below: 1.2em)
	show heading: set text(font: cnfont, weight: "semibold")
	set list(marker: (sym.square.filled.small, [--]), indent: .5em)
	set ref(supplement: it => {
		if it.func() == math.equation {
			"式"
		} else {
			auto
		}
	})

	set par(leading: 0.75em)

	v(0.6fr)
	if logo != none {
		align(right, image(logo, width: 26%))
	}
	v(9.6fr)

	text(4em, weight: "light", font: cnfont, title)
	v(2.4fr)

	pagebreak()
	pagebreak()

	outline(depth: 1)
[
	#counter(page).update(1)
	<PageNumberingStated>
	#set page(footer: locate(loc => {
		if skip_footer.at(loc) {
			return
		}

		let thispage = thispage_number(loc)
		let is_mainpart = query(<MainStarted>, before: loc) != ()
		let is_mainpart = true
		let footer_content = if is_mainpart {
			[\##problem_id.at(loc).first() #footer_title.at(loc)]
		}

		let isleft = calc.even(thispage)
		set align(left)  if isleft
		set align(right) if not isleft
		if isleft { [#thispage] }
		[ #halftab #underline(offset: 2pt, footer_content) #halftab ]
		if not isleft { [#thispage] }
	}))

	// Main body.
	#set par(justify: true)
	#set text(15pt)

	#body
]
}