// Package site assembles the Mode A static site out of content/ and knows how
// to write it to disk.
//
// One assembler, two callers: cmd/build writes the whole site to a directory,
// and cmd/server uses the same view models for the two things that cannot be
// pre-rendered — a keyword search with a query in it, and the streamed stage
// demonstration. Everything else in the running server is a file on disk, so a
// page is never rendered per request and no page needs an AI service.
package site

import (
	"path/filepath"
	"time"

	"github.com/a-h/templ"

	"gitea.lab.audasmedia.com.au/sam/ai-resume/internal/content"
	"gitea.lab.audasmedia.com.au/sam/ai-resume/internal/search"
	"gitea.lab.audasmedia.com.au/sam/ai-resume/internal/stage"
	"gitea.lab.audasmedia.com.au/sam/ai-resume/internal/web/templates"
)

// Config is where the site is read from and written to.
type Config struct {
	// Root is the repository root. Static assets are read from it.
	Root string
	// ContentDir is the Markdown source of truth. Defaults to Root/content.
	ContentDir string
	// OutDir is where Build writes the pre-rendered site. Defaults to Root/dist.
	OutDir string
}

func (c *Config) defaults() {
	if c.Root == "" {
		c.Root = "."
	}
	if c.ContentDir == "" {
		c.ContentDir = filepath.Join(c.Root, "content")
	}
	if c.OutDir == "" {
		c.OutDir = filepath.Join(c.Root, "dist")
	}
}

// Shell is the chrome every page shares. It needs no content tree, so the
// running server can render a search page with only dist/ on disk.
type Shell struct {
	// Year is stamped in the footer.
	Year int
}

// NewShell returns the chrome for the current year.
func NewShell() Shell { return Shell{Year: year()} }

// Nav builds the six-area navigation, marking area as current.
func (Shell) Nav(area string) []templates.NavItem {
	items := make([]templates.NavItem, 0, len(content.Areas))
	for _, a := range content.Areas {
		items = append(items, templates.NavItem{
			Title:   a.Title,
			Href:    "/" + a.Key + "/",
			Gutter:  a.Gutter,
			Current: a.Key == area,
		})
	}
	return items
}

// RouteBinding is the Mode A driver: one pre-rendered fragment per click.
func (Shell) RouteBinding() stage.Binding {
	return stage.RouteDriver{BaseURL: "/stage"}.Bind()
}

// StreamBinding is the Mode B driver: fragments pushed over SSE.
func (Shell) StreamBinding(endpoint string) stage.Binding {
	return stage.SSEDriver{Endpoint: endpoint}.Bind()
}

// LayoutOpts are the per-page chrome values.
type LayoutOpts struct {
	Title       string
	Description string
	Area        string
	Crumbs      []templates.Crumb
	Binding     stage.Binding
}

// Layout builds the chrome for one page. It never looks at the stage driver
// beyond handing the binding to the template.
func (sh Shell) Layout(o LayoutOpts) templates.LayoutView {
	return templates.LayoutView{
		Title:       o.Title,
		Description: o.Description,
		Area:        o.Area,
		Nav:         sh.Nav(o.Area),
		Crumbs:      o.Crumbs,
		Stage:       o.Binding,
		Year:        sh.Year,
	}
}

// SearchView builds the search page. Search is the one Mode A page that reads a
// query, so the server renders it; with JavaScript off the form posts and the
// same page comes back with results.
func (sh Shell) SearchView(indexed int, q string, results []search.Result, failed bool) templates.SearchView {
	return templates.SearchView{
		Layout: sh.Layout(LayoutOpts{
			Title:       "Search — Sam Rolfe",
			Description: "Keyword search across every page of this site. No model, no network call.",
			Crumbs:      []templates.Crumb{{Label: "Home", Href: "/"}, {Label: "Search"}},
			Binding:     sh.RouteBinding(),
		}),
		Query:   q,
		Results: results,
		Indexed: indexed,
		Failed:  failed,
	}
}

// NotFoundPage is the 404, pre-rendered at build time and also served live.
func (sh Shell) NotFoundPage() templates.NotFoundView {
	return templates.NotFoundView{
		Layout: sh.Layout(LayoutOpts{
			Title:       "Page not found — Sam Rolfe",
			Description: "That page is not here. The six areas and the evidence index are the reliable ways in.",
			Crumbs:      []templates.Crumb{{Label: "Home", Href: "/"}, {Label: "Not found"}},
			Binding:     sh.RouteBinding(),
		}),
	}
}

// Site is the content tree plus everything derived from it.
type Site struct {
	Shell
	Config   Config
	Content  *content.Set
	Renderer *content.Renderer

	// Fragments are the pre-rendered stage fragments, in manifest order. The
	// first len(content.Areas) are the six area landing pages, which is the
	// default stream.
	Fragments []*Fragment
	// Manifest indexes the same fragments the way the server sees them.
	Manifest *stage.Manifest
	// FragmentsByDoc lists fragment ids per document, in reading order.
	FragmentsByDoc map[string][]string

	fragByID map[string]*Fragment
}

// New loads content/ and renders every page and stage fragment in memory. It
// touches no network and starts no service.
func New(cfg Config) (*Site, error) {
	cfg.defaults()
	set, err := content.Load(cfg.ContentDir)
	if err != nil {
		return nil, err
	}
	r := content.NewRenderer(set)
	if err := r.Render(); err != nil {
		return nil, err
	}
	s := &Site{
		Shell:          NewShell(),
		Config:         cfg,
		Content:        set,
		Renderer:       r,
		Manifest:       &stage.Manifest{},
		FragmentsByDoc: map[string][]string{},
		fragByID:       map[string]*Fragment{},
	}
	if err := s.buildFragments(); err != nil {
		return nil, err
	}
	return s, nil
}

// PublicDocs returns the published documents: public: true, in navigation order.
func (s *Site) PublicDocs() []*content.Document {
	out := make([]*content.Document, 0, len(s.Content.Docs))
	for _, d := range s.Content.Docs {
		if d.Public {
			out = append(out, d)
		}
	}
	return out
}

// PublicInArea returns the published documents of one area, L1 first.
func (s *Site) PublicInArea(area string) []*content.Document {
	var out []*content.Document
	for _, d := range s.PublicDocs() {
		if d.Area == area {
			out = append(out, d)
		}
	}
	return out
}

// pageCount counts published pages in an area.
func (s *Site) pageCount(area string) int { return len(s.PublicInArea(area)) }

// artefactCount counts every resolved artefact on the site.
func (s *Site) artefactCount() int {
	n := 0
	for _, d := range s.PublicDocs() {
		n += len(d.Artefacts)
	}
	return n
}

// Home is the landing page view: the ninety-second read.
func (s *Site) Home() templates.HomeView {
	cardArea := func(a content.Area) templates.PillarCardView {
		card := templates.PillarCardView{
			Area:    a,
			Title:   a.Title,
			Claim:   a.Blurb,
			Href:    "/" + a.Key + "/",
			Level:   1,
			Pages:   s.pageCount(a.Key),
			Metrics: []templates.MetricView{},
			Tech:    []string{},
		}
		if d, ok := s.Content.AreaLanding(a.Key); ok {
			card.Claim = d.Claim
			card.Confidence = d.Confidence
			card.Title = d.Title
			for _, m := range d.Metrics {
				card.Metrics = append(card.Metrics, templates.MetricView{Label: m.Label, Value: content.MetricValue(m.Value)})
			}
			card.Tech = d.Tech
		}
		return card
	}
	cards := make([]templates.PillarCardView, 0, len(content.Areas))
	for _, a := range content.Areas {
		cards = append(cards, cardArea(a))
	}
	return templates.HomeView{
		Layout: s.Layout(LayoutOpts{
			Title:       "Sam Rolfe — AI systems, the platforms under them, the hardware at the edge",
			Description: content.Positioning + " " + content.SupportLine,
			Crumbs:      []templates.Crumb{{Label: "Home"}},
			Binding:     s.RouteBinding(),
		}),
		Positioning: content.Positioning,
		Support:     content.SupportLine,
		Location:    content.Location,
		Cards:       cards,
		Artifacts:   s.artefactCount(),
		Pages:       len(s.PublicDocs()),
		Areas:       len(content.Areas),
	}
}

// Doc builds the view for one document at any depth.
func (s *Site) Doc(d *content.Document) templates.DocView {
	area, _ := content.AreaByKey(d.Area)
	levelLabel := templates.LevelLabel(d.Level)

	view := templates.DocView{
		Layout: s.Layout(LayoutOpts{
			Title:       d.Title + " — Sam Rolfe",
			Description: content.Truncate(d.Claim, 160),
			Area:        d.Area,
			Crumbs:      s.crumbs(d),
			Binding:     s.RouteBinding(),
		}),
		Doc:        d,
		AreaTitle:  area.Title,
		Role:       area.Role,
		Body:       templates.MarkdownBody(d.HTML),
		Metrics:    make([]templates.MetricView, 0, len(d.Metrics)),
		Tech:       d.Tech,
		Evidence:   s.evidence(d),
		Backlinks:  s.backlinks(d),
		SubPages:   s.subPages(d),
		LevelLabel: levelLabel,
	}
	for _, m := range d.Metrics {
		view.Metrics = append(view.Metrics, templates.MetricView{Label: m.Label, Value: content.MetricValue(m.Value)})
	}
	if d.Area == "history" && d.Level <= 2 {
		view.Timeline = s.timeline(d.Area)
	}
	return view
}

func (s *Site) crumbs(d *content.Document) []templates.Crumb {
	area, _ := content.AreaByKey(d.Area)
	out := []templates.Crumb{
		{Label: "Home", Href: "/"},
		{Label: area.Title, Href: "/" + d.Area + "/"},
	}
	if d.Level > 1 {
		out = append(out, templates.Crumb{Label: d.Title, Href: d.URL})
	}
	return out
}

// evidence turns each artefact into a row that loads the artefact into the
// stage panel and is also a working link.
func (s *Site) evidence(d *content.Document) []templates.LinkView {
	out := make([]templates.LinkView, 0, len(d.Artefacts))
	ids := s.FragmentsByDoc[d.ID]
	for _, a := range d.Artefacts {
		ra, err := s.Content.Resolve(d, a)
		if err != nil {
			// Load already rejected dangling artefacts; keep going rather than
			// render a broken link.
			continue
		}
		conf := d.Confidence
		if ra.Target != nil {
			conf = ra.Target.Confidence
		}
		link := templates.LinkView{
			Label:      a.Label,
			Href:       ra.Href,
			Kind:       ra.Kind,
			Confidence: conf,
		}
		for _, id := range ids {
			if f, ok := s.fragByID[id]; ok && f.ArtefactURL == a.URL {
				link.HXGet = s.RouteFragmentURL(id)
			}
		}
		out = append(out, link)
	}
	return out
}

func (s *Site) backlinks(d *content.Document) []templates.LinkView {
	out := make([]templates.LinkView, 0, len(d.Backlinks))
	for _, b := range d.Backlinks {
		out = append(out, templates.LinkView{Label: b.Title, Href: b.URL, Kind: templates.LevelLabel(b.Level)})
	}
	return out
}

// subPages is the drill-down list under a page. L1 lists the capability pages
// in its area; every other level lists artefacts in the area that this page
// does not already cite, so no page can become unreachable.
func (s *Site) subPages(d *content.Document) []templates.LinkView {
	cited := map[string]bool{}
	for _, a := range d.Artefacts {
		if ra, err := s.Content.Resolve(d, a); err == nil && ra.Target != nil {
			cited[ra.Target.ID] = true
		}
	}
	var out []templates.LinkView
	for _, other := range s.PublicInArea(d.Area) {
		if other.ID == d.ID || cited[other.ID] {
			continue
		}
		if d.Level == 1 && other.Level != 2 {
			continue
		}
		if d.Level > 1 && other.Level < 3 {
			continue
		}
		out = append(out, templates.LinkView{
			Label: other.Title,
			Href:  other.URL,
			Kind:  other.Confidence,
		})
	}
	return out
}

// timeline orders an area's deeper pages by period, newest first.
func (s *Site) timeline(area string) []templates.TimelineItem {
	var items []templates.TimelineItem
	for _, d := range s.PublicInArea(area) {
		if d.Level < 2 {
			continue
		}
		items = append(items, templates.TimelineItem{
			Period:     d.Period,
			Title:      d.Title,
			Href:       d.URL,
			Confidence: d.Confidence,
			Claim:      d.Claim,
		})
	}
	return items
}

// Evidence is the one-page index of every artefact on the site.
func (s *Site) Evidence() templates.EvidenceView {
	var groups []templates.EvidenceGroup
	total := 0
	for _, a := range content.Areas {
		group := templates.EvidenceGroup{AreaTitle: a.Title, Href: "/" + a.Key + "/"}
		for _, d := range s.PublicInArea(a.Key) {
			for _, l := range s.evidence(d) {
				group.Rows = append(group.Rows, templates.EvidenceRow{
					Label:      d.Title + " · " + l.Label,
					Href:       l.Href,
					HXGet:      l.HXGet,
					Kind:       l.Kind,
					Confidence: l.Confidence,
				})
				total++
			}
		}
		if len(group.Rows) > 0 {
			groups = append(groups, group)
		}
	}
	return templates.EvidenceView{
		Layout: s.Layout(LayoutOpts{
			Title:       "Evidence index — Sam Rolfe",
			Description: "Every artefact this site claims, on one page.",
			Crumbs:      []templates.Crumb{{Label: "Home", Href: "/"}, {Label: "Evidence"}},
			Binding:     s.RouteBinding(),
		}),
		Groups: groups,
		Total:  total,
	}
}

// StreamKeys is the fragment sequence the streaming panel demonstrates: the six
// area landing fragments, in navigation order. No model is involved.
func (s *Site) StreamKeys() []string {
	n := len(content.Areas)
	if n > len(s.Fragments) {
		n = len(s.Fragments)
	}
	keys := make([]string, 0, n)
	for _, f := range s.Fragments[:n] {
		keys = append(keys, f.ID)
	}
	return keys
}

// Stream is the page that re-points the panel at an event stream. The layout is
// the same as every other page; only the binding differs.
func (s *Site) Stream(endpoint string) templates.StreamView {
	keys := s.StreamKeys()
	links := make([]templates.LinkView, 0, len(keys))
	for _, id := range keys {
		if f, ok := s.fragByID[id]; ok {
			links = append(links, templates.LinkView{
				Label: f.Title,
				Href:  s.DocURL(f.DocID),
				HXGet: s.RouteFragmentURL(id),
				Kind:  f.Kind,
			})
		}
	}
	return templates.StreamView{
		Layout: s.Layout(LayoutOpts{
			Title:       "Streaming panel — Sam Rolfe",
			Description: "The presentation panel bound to an event stream instead of pre-rendered files.",
			Crumbs:      []templates.Crumb{{Label: "Home", Href: "/"}, {Label: "Streaming panel"}},
			Binding:     s.StreamBinding(endpoint),
		}),
		Frames:   len(links),
		Fragment: links,
	}
}

// DocURL is the published URL for a document id.
func (s *Site) DocURL(id string) string {
	if d, ok := s.Content.ByID(id); ok {
		return d.URL
	}
	return "/"
}

// RouteFragmentURL is where the route driver's fragment file is served from.
func (s *Site) RouteFragmentURL(id string) string {
	return stage.RouteDriver{BaseURL: "/stage"}.FragmentURL(id)
}

// Fragment is one pre-rendered stage fragment.
type Fragment struct {
	ID    string
	DocID string
	Kind  string
	Title string
	// ArtefactURL is the artefact this fragment was built from, if any. It is
	// how an evidence row finds the fragment that belongs to it.
	ArtefactURL string
	// File is relative to the published root, e.g. stage/doc-edge-overview.html.
	File string
	// HTML is the rendered fragment markup, written to File at build time.
	HTML string

	subtitle   string
	body       templ.Component
	code       *stage.Code
	src        string
	alt        string
	links      []stage.Link
	confidence string
	docURL     string
	docTitle   string
}

// Fragment returns a pre-rendered fragment by id.
func (s *Site) Fragment(id string) (*Fragment, bool) {
	f, ok := s.fragByID[id]
	return f, ok
}

func year() int { return time.Now().Year() }