// model.go — the log projected into a browsable model.
//
// Everything the site shows is derived here from the notevi log alone: agents and
// their colors, per-file coverage bitmasks, notes, and live session activity.
// The private jj sidecar is the only state.
package web

import (
	"encoding/json"
	"fmt"
	"html/template"
	"sort"
	"strings"
	"time"
)

// Coverage is a uint8 bitmask, so only the first maxAgents agents get a color;
// later ones fall back to the muted "no bit" rendering.
const maxAgents = 8

type Entry struct {
	Time    string `json:"time,omitempty"`
	Op      string `json:"op"`
	Session string `json:"session,omitempty"`
	Agent   string `json:"agent,omitempty"`
	Model   string `json:"model,omitempty"`
	Reason  string `json:"reasoning,omitempty"`
	Dir     string `json:"dir,omitempty"`
	Rev     string `json:"rev,omitempty"`
	Change  string `json:"change,omitempty"`
	Commit  string `json:"commit,omitempty"`
	File    string `json:"file,omitempty"`
	Start   int    `json:"start,omitempty"`
	End     int    `json:"end,omitempty"`
	Pattern string `json:"pattern,omitempty"`
	Matches int    `json:"matches,omitempty"`
	NoteID  int    `json:"note_id,omitempty"`
	ReplyTo int    `json:"reply_to,omitempty"`
	Type    string `json:"type,omitempty"`
	Text    string `json:"text,omitempty"`
}

type Agent struct {
	Name, Short, Session, Model, Reason string
	Bit                                 uint8
	Reads, Greps, Notes                 int
}

type Note struct {
	ID                                    int // position in the log, for anchors
	NoteID                                int // the agent's own per-session number
	Agent                                 *Agent
	Session, Model, Reason                string
	File, Kind, Text, Change, Commit, Rev string
	Start, End                            int
	ReplyTo                               int
	Replies, Mentions                     []*Note // notes that point back to this one
	At                                    time.Time
	When, Ago                             string
}

// ThreadNode is the tree-shaped rendering of the note DAG. A note reached by
// more than one path is emitted fully once and then as a compact reference, so
// the focused page keeps valid DOM ids and cannot recurse through malformed
// cyclic logs.
type ThreadNode struct {
	Note      *Note
	Via       string // "reply" | "mention"; empty for the focused root
	Children  []*ThreadNode
	Reference bool
}

type File struct {
	Path, Change        string
	Traced              bool
	Stub                string      // set when content is not rendered (binary, huge)
	Cov                 []uint8     // 1-based line -> agent bitmask
	NoteAt              map[int]int // line -> index into Notes
	Reads, Greps        int
	Patterns            []string
	Notes               []*Note
	Total, Covered, Pct int
	Mask                uint8
	Body                template.HTML
}

type Site struct {
	Title   string
	Repo    string
	Change  string // the change most entries were logged at
	Only    string // the change this view is scoped to ("" = the whole log)
	Agents  []*Agent
	Files   map[string]*File // traced files
	Order   []string         // traced paths, sorted
	All     []*File          // every file in the repo at the site change
	Notes   []*Note          // in scope
	Entries []Entry          // the whole log, scope or no scope
	Theme   *Theme           // dark
	Light   *Theme

	// counted over the whole log, so a scoped view can still say what it is
	// not showing
	NotesTotal int
	NotesAt    map[string]int // change -> notes recorded there
	Votes      map[string]int // change -> entries recorded there
	Ranked     []string       // changes, most-logged first
}

// buildModel projects log entries onto agents, files and notes. It never
// touches the repo, so it is cheap enough to redo on every log change.
//
// only, when set, keeps just what was recorded at that change: a read logged
// against another change points at line numbers that have since moved, so a
// view of one change must not inherit them. Two things stay whole-log
// regardless — agent colors, so they do not shuffle when the scope changes,
// and note ids, so a link to a note survives it.
func buildModel(title string, entries []Entry, only string) *Site {
	s := &Site{Title: title, Only: only, Files: map[string]*File{}, Entries: entries,
		NotesAt: map[string]int{}, Votes: map[string]int{}}
	agents := map[string]*Agent{}
	noteN := 0
	for _, e := range entries {
		if e.Agent == "" {
			e.Agent = "unknown"
		}
		a := agents[e.Agent]
		if a == nil {
			a = &Agent{Name: e.Agent, Short: strings.SplitN(e.Agent, "_", 2)[0],
				Session: e.Session, Model: e.Model, Reason: e.Reason}
			if len(s.Agents) < maxAgents {
				a.Bit = 1 << len(s.Agents)
			}
			agents[e.Agent] = a
			s.Agents = append(s.Agents, a)
		}
		if e.Change != "" {
			s.Votes[e.Change]++
		}
		if e.Op == "note" {
			noteN++
			s.NotesTotal++
			s.NotesAt[e.Change]++
		}
		if only != "" && e.Change != only {
			continue
		}
		switch e.Op {
		case "read":
			a.Reads++
			f := s.file(e.File, e.Change)
			f.Reads++
			f.cover(e.Start, e.End, a.Bit)
		case "grep":
			a.Greps++
			if f, ok := s.Files[e.File]; ok || e.File != "" {
				if f == nil { // grep on a file we later read
					f = s.file(e.File, e.Change)
				}
				f.Greps++
				f.Patterns = append(f.Patterns, fmt.Sprintf("%s (%d)", e.Pattern, e.Matches))
			}
		case "note":
			a.Notes++
			at := parseTime(e.Time)
			n := &Note{ID: noteN, NoteID: e.NoteID, Agent: a, Session: e.Session,
				Model: e.Model, Reason: e.Reason, File: e.File, Change: e.Change,
				Commit: e.Commit, Rev: e.Rev, Start: e.Start, End: e.End, ReplyTo: e.ReplyTo,
				Kind: e.Type, Text: e.Text,
				At: at, When: stamp(at), Ago: ago(at)}
			s.Notes = append(s.Notes, n)
			if e.File != "" {
				f := s.file(e.File, e.Change)
				f.Notes = append(f.Notes, n)
			}
		}
	}
	for c := range s.Votes {
		s.Ranked = append(s.Ranked, c)
	}
	// most-logged first; ties by id so the pick is stable across rebuilds
	sort.Slice(s.Ranked, func(i, j int) bool {
		a, b := s.Ranked[i], s.Ranked[j]
		if s.Votes[a] != s.Votes[b] {
			return s.Votes[a] > s.Votes[b]
		}
		return a < b
	})
	if len(s.Ranked) > 0 {
		s.Change = s.Ranked[0]
	}
	// drop grep-only "files" that are really path filters (dirs, non-files)
	for p, f := range s.Files {
		if f.Reads == 0 && len(f.Notes) == 0 {
			delete(s.Files, p)
		}
	}
	for p := range s.Files {
		s.Order = append(s.Order, p)
	}
	sort.Strings(s.Order)
	linkNotes(s.Notes)
	return s
}

func (s *Site) file(path, change string) *File {
	f := s.Files[path]
	if f == nil {
		f = &File{Path: path, NoteAt: map[int]int{}, Traced: true}
		s.Files[path] = f
	}
	if change != "" {
		f.Change = change
	}
	return f
}

func (f *File) cover(start, end int, bit uint8) {
	if start < 1 {
		return
	}
	if end < start {
		end = start
	}
	for len(f.Cov) <= end {
		f.Cov = append(f.Cov, 0)
	}
	for i := start; i <= end; i++ {
		f.Cov[i] |= bit
	}
	f.Mask |= bit
}

// clone copies the per-render state so one *File from the model can be
// rendered concurrently at several revisions. Cov is read-only during render.
func (f *File) clone() *File {
	c := *f
	c.NoteAt = map[int]int{}
	c.Notes = append([]*Note(nil), f.Notes...)
	return &c
}

// filesAt joins a revision's path list with the traced files, so untraced
// files still appear in the tree. Traced *File values are shared read-only.
func (s *Site) filesAt(paths []string, change string) []*File {
	var all []*File
	for _, p := range paths {
		if p == "" {
			continue
		}
		f := s.Files[p]
		if f == nil {
			f = &File{Path: p, Change: change, NoteAt: map[int]int{}}
		} else {
			f.Traced = true
		}
		all = append(all, f)
	}
	sort.Slice(all, func(i, j int) bool { return all[i].Path < all[j].Path })
	return all
}

// masks lists every bitmask combination the colored agents can produce.
func (s *Site) masks() []uint8 {
	n := len(s.Agents)
	if n > maxAgents {
		n = maxAgents
	}
	var out []uint8
	for m := 1; m < 1<<n; m++ {
		out = append(out, uint8(m))
	}
	return out
}

// ── notes: filtering and facets ───────────────────────────────────────────

type NoteFilter struct {
	Text    string // substring of the note body
	File    string // substring of the file path
	Agent   string
	Model   string
	Session string
	Kind    string
	Change  string
	From    string // YYYY-MM-DD, inclusive
	To      string // YYYY-MM-DD, inclusive
}

func (f NoteFilter) empty() bool { return f == NoteFilter{} }

func (f NoteFilter) match(n *Note) bool {
	has := func(hay, needle string) bool {
		return needle == "" || strings.Contains(strings.ToLower(hay), strings.ToLower(needle))
	}
	if !has(n.Text, f.Text) || !has(n.File, f.File) {
		return false
	}
	eq := func(got, want string) bool { return want == "" || got == want }
	if !eq(n.Agent.Name, f.Agent) || !eq(n.Model, f.Model) || !eq(n.Session, f.Session) ||
		!eq(n.Kind, f.Kind) || !eq(n.Change, f.Change) {
		return false
	}
	if f.From != "" && (n.At.IsZero() || n.At.Format(dateFmt) < f.From) {
		return false
	}
	if f.To != "" && (n.At.IsZero() || n.At.Format(dateFmt) > f.To) {
		return false
	}
	return true
}

const dateFmt = "2006-01-02"

// FilterNotes returns matching notes, newest first (undated notes last).
func (s *Site) FilterNotes(f NoteFilter) []*Note {
	var out []*Note
	for _, n := range s.Notes {
		if f.match(n) {
			out = append(out, n)
		}
	}
	sort.SliceStable(out, func(i, j int) bool { return out[i].At.After(out[j].At) })
	return out
}

// NoteByID finds a note by the id a permalink names. Ids count over the whole
// log and the log only ever grows, so the link a reader was given goes on
// meaning the same note however the site is later scoped or rebuilt.
func (s *Site) NoteByID(id int) *Note {
	for _, n := range s.Notes {
		if n.ID == id {
			return n
		}
	}
	return nil
}

// linkNotes derives the graph without adding another log operation. Replies
// are explicit reply_to edges; mentions are ordinary local Markdown links to
// /note/N (or an equivalent relative path). If a reply also links its parent,
// the explicit relationship wins and the child is not counted twice.
func linkNotes(notes []*Note) {
	byID := make(map[int]*Note, len(notes))
	for _, n := range notes {
		byID[n.ID] = n
	}
	links := newNoteLinkParser()
	for _, child := range notes {
		if parent := byID[child.ReplyTo]; parent != nil && parent != child {
			parent.Replies = append(parent.Replies, child)
		}
		for _, id := range noteLinks(links, child.Text) {
			parent := byID[id]
			if parent == nil || parent == child || id == child.ReplyTo {
				continue
			}
			parent.Mentions = append(parent.Mentions, child)
		}
	}
}

// NoteThread expands replies and mentions together, oldest first. The global
// seen set turns a DAG into one readable Hacker News-style thread while still
// leaving a reference at every additional incoming edge.
func (s *Site) NoteThread(id int) *ThreadNode {
	root := s.NoteByID(id)
	if root == nil {
		return nil
	}
	seen := map[int]bool{id: true}
	var build func(*Note) *ThreadNode
	build = func(n *Note) *ThreadNode {
		node := &ThreadNode{Note: n}
		for _, edge := range noteEdges(n) {
			child := &ThreadNode{Note: edge.Note, Via: edge.Via}
			if seen[edge.Note.ID] {
				child.Reference = true
			} else {
				seen[edge.Note.ID] = true
				child = build(edge.Note)
				child.Via = edge.Via
			}
			node.Children = append(node.Children, child)
		}
		return node
	}
	return build(root)
}

type noteEdge struct {
	Note *Note
	Via  string
}

func noteEdges(n *Note) []noteEdge {
	seen := map[int]bool{}
	edges := make([]noteEdge, 0, len(n.Replies)+len(n.Mentions))
	for _, child := range n.Replies {
		seen[child.ID] = true
		edges = append(edges, noteEdge{Note: child, Via: "reply"})
	}
	for _, child := range n.Mentions {
		if !seen[child.ID] {
			edges = append(edges, noteEdge{Note: child, Via: "mention"})
		}
	}
	sort.SliceStable(edges, func(i, j int) bool { return edges[i].Note.ID < edges[j].Note.ID })
	return edges
}

// Facets are the distinct values the note filters can select, so the form
// only ever offers choices that exist in the log.
type Facets struct {
	Agents, Models, Sessions, Kinds, Changes, Files []string
}

func (s *Site) Facets() *Facets {
	fa := &Facets{}
	add := func(dst *[]string, seen map[string]bool, v string) {
		if v != "" && !seen[v] {
			seen[v] = true
			*dst = append(*dst, v)
		}
	}
	ag, mo, se, ki, ch, fi := map[string]bool{}, map[string]bool{}, map[string]bool{}, map[string]bool{}, map[string]bool{}, map[string]bool{}
	for _, n := range s.Notes {
		add(&fa.Agents, ag, n.Agent.Name)
		add(&fa.Models, mo, n.Model)
		add(&fa.Sessions, se, n.Session)
		add(&fa.Kinds, ki, n.Kind)
		add(&fa.Changes, ch, n.Change)
		add(&fa.Files, fi, n.File)
	}
	for _, s := range [][]string{fa.Agents, fa.Models, fa.Sessions, fa.Kinds, fa.Changes, fa.Files} {
		sort.Strings(s)
	}
	return fa
}

// nextNoteID mirrors notevi's numbering: ids count up from 1 within a session.
func nextNoteID(entries []Entry, session string) int {
	max := 0
	for _, e := range entries {
		if e.Op == "note" && e.Session == session && e.NoteID > max {
			max = e.NoteID
		}
	}
	return max + 1
}

// ── live activity ─────────────────────────────────────────────────────────

// A Session is one agent run seen in the log: who it is, what it last did,
// and whether it is still going. This is what "live" shows.
type Session struct {
	ID, Agent, Short, Model, Reason, Dir string
	Bit                                  uint8
	Last                                 time.Time
	Ago, LastOp, File                    string
	Change                               string
	Reads, Greps, Notes                  int
	Live                                 bool
}

// Sessions groups the log by session (falling back to agent+dir for logs
// without one), newest activity first. Sessions touched within window are
// reported as live.
func (s *Site) Sessions(now time.Time, window time.Duration, limit int) []*Session {
	byKey := map[string]*Session{}
	var order []*Session
	byName := map[string]*Agent{}
	for _, a := range s.Agents {
		byName[a.Name] = a
	}
	for _, e := range s.Entries {
		name := e.Agent
		if name == "" {
			name = "unknown"
		}
		key := e.Session
		if key == "" {
			key = name + "\x00" + e.Dir
		}
		v := byKey[key]
		if v == nil {
			a := byName[name]
			v = &Session{ID: e.Session, Agent: name, Dir: e.Dir}
			if a != nil {
				v.Short, v.Bit = a.Short, a.Bit
			}
			byKey[key] = v
			order = append(order, v)
		}
		if e.Model != "" {
			v.Model, v.Reason = e.Model, e.Reason
		}
		if e.Dir != "" {
			v.Dir = e.Dir
		}
		if e.Change != "" {
			v.Change = e.Change
		}
		switch e.Op {
		case "read":
			v.Reads++
		case "grep":
			v.Greps++
		case "note":
			v.Notes++
		}
		if at := parseTime(e.Time); !at.IsZero() && at.After(v.Last) {
			v.Last, v.File, v.LastOp = at, e.File, describe(e)
		}
	}
	for _, v := range order {
		v.Ago = agoFrom(now, v.Last)
		v.Live = !v.Last.IsZero() && now.Sub(v.Last) < window
	}
	sort.SliceStable(order, func(i, j int) bool { return order[i].Last.After(order[j].Last) })
	if limit > 0 && len(order) > limit {
		order = order[:limit]
	}
	return order
}

func describe(e Entry) string {
	switch e.Op {
	case "read":
		if e.Start > 0 {
			if e.End > e.Start {
				return fmt.Sprintf("read %s:%d-%d", e.File, e.Start, e.End)
			}
			return fmt.Sprintf("read %s:%d", e.File, e.Start)
		}
		return "read " + e.File
	case "grep":
		if e.File != "" {
			return fmt.Sprintf("grep %q in %s (%d)", e.Pattern, e.File, e.Matches)
		}
		return fmt.Sprintf("grep %q (%d)", e.Pattern, e.Matches)
	case "note":
		if e.File != "" {
			return "note on " + e.File
		}
		return "note"
	}
	return e.Op
}

// ── sidecar JSONL ─────────────────────────────────────────────────────────

func parseLog(b []byte) []Entry {
	var entries []Entry
	for _, line := range strings.Split(string(b), "\n") {
		if line == "" {
			continue
		}
		var e Entry
		if json.Unmarshal([]byte(line), &e) == nil {
			entries = append(entries, e)
		}
	}
	return entries
}

func readLog(log logStore) []Entry {
	b, err := log.Read()
	if err != nil {
		fatal("%v", err)
	}
	return parseLog(b)
}

func appendEntry(log logStore, e *Entry) error {
	return log.Append(func(current []byte) ([]byte, error) {
		e.NoteID = nextNoteID(parseLog(current), e.Session)
		b, err := json.Marshal(e)
		return append(b, '\n'), err
	})
}

// ── time ──────────────────────────────────────────────────────────────────

func parseTime(s string) time.Time {
	if s == "" {
		return time.Time{}
	}
	t, err := time.Parse(time.RFC3339, s)
	if err != nil {
		return time.Time{}
	}
	return t
}

func stamp(t time.Time) string {
	if t.IsZero() {
		return ""
	}
	return t.Local().Format("2006-01-02 15:04")
}

func ago(t time.Time) string { return agoFrom(time.Now(), t) }

func agoFrom(now, t time.Time) string {
	if t.IsZero() {
		return ""
	}
	d := now.Sub(t)
	switch {
	case d < 0:
		return "just now"
	case d < time.Minute:
		return fmt.Sprintf("%ds ago", int(d.Seconds()))
	case d < time.Hour:
		return fmt.Sprintf("%dm ago", int(d.Minutes()))
	case d < 24*time.Hour:
		return fmt.Sprintf("%dh ago", int(d.Hours()))
	default:
		return fmt.Sprintf("%dd ago", int(d.Hours())/24)
	}
}