// The types in this file are the theme contract in Go: what a template receives, nothing about how it is
// produced. Split from render.go when that file crossed the size warning — the seam was already here, since
// docs/theme-contract.md describes exactly this and nothing else.

package render

import (
	"html/template"
	"time"

	"khosra/internal/content"
)

// head is what every kind of page shares: the document shell the base template needs. Absence is the
// zero value — a template reads what exists and never fails on a missing field (invariant 1).
type head struct {
	// Title may be empty for a bundle; a listing always has one.
	Title string
	// Lang is the locale being served.
	Lang string
	// Canonical is the permalink of what was actually served, which differs from the URL requested when
	// the fallback chain supplied another language (ADR-0009).
	Canonical string
	// Alternates lists every language this key exists in, for hreflang.
	Alternates []Alternate
	// Style is the reference theme's stylesheet, inlined so a bare site root needs no asset route.
	Style template.CSS
	// Site is what the site declared about itself in site.yaml (ADR-0039). Zero when it declared nothing.
	Site content.Settings
	// Sections are the site's sections, for navigation: only .Title and .URL are set. Empty until the engine is
	// told where to find them, which cmd does at wiring time (ADR-0049).
	Sections []Item
}

// Page is one bundle rendered.
type Page struct {
	head
	// Key is the bundle's identity, useful for building links.
	Key string
	// HTML is the rendered body.
	HTML template.HTML
	// Extra carries every frontmatter key the parser does not name (ADR-0002).
	Extra map[string]any
	// Sequence is the series this page sits in, nil when it sits in none.
	Sequence *Sequence
	// Tags are this bundle's own terms, each with the URL of its listing. Empty when it carries none.
	Tags []Item
	// ExtrasURL links this bundle's supporting files, empty when it has none — so a theme can offer them
	// without guessing whether they exist (ADR-0047).
	ExtrasURL string
}

// Sequence is a series as a page sees it: its members in reading order, and where this page is in them
// (ADR-0033).
type Sequence struct {
	// Title is the series' title, empty when the landing page omits one; URL is its permalink.
	Title, URL string
	// Members are every entry in reading order — ascending, unlike a dated listing.
	Members []Item
	// Index is this page's 1-based position, zero when this page is the series landing itself. Count is
	// how many members there are.
	Index, Count int
	// Prev and Next are the neighbours in reading order, nil at the ends and on the landing page. Prev is
	// the *earlier* entry, the opposite sense of a listing's PrevURL.
	Prev, Next *Item
	// First and Last are the ends of the series, set whenever it has members.
	First, Last *Item
}

// Extras is a bundle's supporting files, browsable (ADR-0047).
type Extras struct {
	head
	// Bundle is the page these files belong to, so a theme has its title and a way back.
	Bundle Item
	// Entries is the whole tree, sorted by path.
	Entries []content.Entry
	// Selected is the entry the URL named, nil on the bare listing.
	Selected *Selected
}

// Selected is the entry a request picked out of the tree.
type Selected struct {
	content.Entry
	// HTML is the rendered file for a markdown or text entry, empty for anything else.
	HTML template.HTML
	// RawURL always works: it is how a theme embeds an image, links a PDF, or offers a download.
	RawURL string
}

// List is a collection page: the result of a Query, one page of it.
type List struct {
	head
	// Items are the entries on this page, in the Query's order.
	Items []Item
	// Page is 1-based; Pages is the total, at least 1 even when empty.
	Page, Pages int
	// PrevURL and NextURL are empty at the ends. Newer is "prev" because the order is newest first.
	PrevURL, NextURL string
	// Groups is the same entries partitioned by section, set alongside Items for a tag listing. Both shapes
	// are offered because which one to show is the theme's decision, not the engine's (ADR-0046).
	Groups []Group
}

// Group is a named run of entries within a listing.
type Group struct {
	Name  string
	Items []Item
}

// Item is one entry in a listing.
type Item struct {
	Title string
	Key   string
	URL   string
	Date  time.Time
	// Section is the entry's top-level section, so a flat listing can label where an entry came from without
	// the engine deciding that it must be grouped (ADR-0046).
	Section string
}

// Alternate is one language a bundle exists in.
type Alternate struct {
	Lang string
	// URL is absolute when the site declares a base, because hreflang is read by machines that resolve nothing
	// against the page.
	URL string
	// Path is the same address, root-relative — what a *visible* language link wants. Found by looking at a
	// rendered page: using URL sent a reader from a local server to the canonical host (ADR-0049).
	Path string
}