package cli

import (
	"fmt"
	"io/fs"
	"sort"
	"strings"

	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
	"github.com/spf13/cobra"

	llmgw "gitea.mynodes.xyz/ilker/llmgw"
)

// The manual: every document the project has, carried in the binary, and a
// page for every command built from the commands themselves — read like man
// or info, in the console or with `llmgw docs`, on a machine with no checkout
// and no browser.

type docTopic struct {
	key   string // what `llmgw docs KEY` takes
	title string
	src   func() string
}

// docOrder is the documents in the order someone new reads them.
var docOrder = []string{"console", "quickstart", "quick-install", "install", "node-onboarding", "onboarding",
	"choosing-models", "fabrics", "facility-aware-placement", "data", "reference"}

func docTopics() []docTopic {
	read := func(path string) func() string {
		return func() string {
			b, err := fs.ReadFile(llmgw.Docs, path)
			if err != nil {
				return "# " + path + "\n\nNot in this build."
			}
			return string(b)
		}
	}
	titleOf := func(path string) string {
		b, _ := fs.ReadFile(llmgw.Docs, path)
		for _, l := range strings.Split(string(b), "\n") {
			if strings.HasPrefix(l, "# ") {
				return strings.TrimPrefix(l, "# ")
			}
		}
		return path
	}
	var out []docTopic
	seen := map[string]bool{}
	add := func(key, path string) {
		if seen[key] {
			return
		}
		if _, err := fs.Stat(llmgw.Docs, path); err != nil {
			return
		}
		seen[key] = true
		out = append(out, docTopic{key: key, title: titleOf(path), src: read(path)})
	}
	for _, k := range docOrder {
		add(k, "docs/"+k+".md")
		if k == "reference" {
			out = append(out, docTopic{key: "commands", title: "Commands", src: commandsManual})
			seen["commands"] = true
		}
	}
	// Any document not placed above, so a new one is never missing.
	entries, _ := fs.ReadDir(llmgw.Docs, "docs")
	var rest []string
	for _, e := range entries {
		rest = append(rest, strings.TrimSuffix(e.Name(), ".md"))
	}
	sort.Strings(rest)
	for _, k := range rest {
		add(k, "docs/"+k+".md")
	}
	add("readme", "README.md")
	add("changes", "CHANGELOG.md")
	return out
}

func findTopic(topics []docTopic, key string) int {
	key = strings.ToLower(strings.TrimSuffix(key, ".md"))
	for i, t := range topics {
		if t.key == key {
			return i
		}
	}
	for i, t := range topics {
		if strings.Contains(strings.ToLower(t.title), key) || strings.HasPrefix(t.key, key) {
			return i
		}
	}
	return -1
}

// commandsManual is a page for every command, from its own help.
func commandsManual() string {
	var b strings.Builder
	b.WriteString("# Commands\n\nEvery command, as `llmgw COMMAND --help` describes it. " +
		"Run bare, in a terminal, `llmgw` opens the setup screens or the console instead.\n")
	var walk func(c *cobra.Command)
	walk = func(c *cobra.Command) {
		if c.Hidden || c.Name() == "help" || c.Name() == "completion" {
			return
		}
		if c.HasParent() {
			level := min(strings.Count(c.CommandPath(), " ")+1, 4)
			fmt.Fprintf(&b, "\n%s %s\n\n", strings.Repeat("#", level), c.CommandPath())
			if c.Long != "" {
				b.WriteString(c.Long + "\n")
			} else if c.Short != "" {
				b.WriteString(c.Short + ".\n")
			}
			b.WriteString("\n```\n" + c.UseLine() + "\n")
			if c.Example != "" {
				b.WriteString("\n" + strings.TrimRight(c.Example, "\n") + "\n")
			}
			if fl := c.LocalFlags(); fl.HasAvailableFlags() {
				b.WriteString("\n" + strings.TrimRight(fl.FlagUsagesWrapped(100), "\n") + "\n")
			}
			b.WriteString("```\n")
		}
		subs := c.Commands()
		sort.Slice(subs, func(i, j int) bool { return subs[i].Name() < subs[j].Name() })
		for _, s := range subs {
			walk(s)
		}
	}
	walk(Root())
	return b.String()
}

// --- markdown, for a terminal ---

var (
	mdH1   = lipgloss.NewStyle().Bold(true).Foreground(tuiAccent).Underline(true)
	mdH2   = lipgloss.NewStyle().Bold(true).Foreground(tuiAccent)
	mdH3   = lipgloss.NewStyle().Bold(true)
	mdCode = lipgloss.NewStyle().Foreground(lipgloss.AdaptiveColor{Light: "#8A4B08", Dark: "#E5C07B"})
	mdBold = lipgloss.NewStyle().Bold(true)
	mdHit  = lipgloss.NewStyle().Reverse(true)
	mdEm   = lipgloss.NewStyle().Italic(true)
	mdLink = lipgloss.NewStyle().Underline(true)
)

// docLine is one line of a rendered document: as shown, as plain text for
// searching, and its heading level if it is one.
type docLine struct {
	text, plain string
	heading     int
}

type mdRun struct {
	text  string
	style *lipgloss.Style
	link  string
}

// inline splits markdown's inline markup into styled runs.
func inline(s string) []mdRun {
	var out []mdRun
	plain := func(t string) {
		if t != "" {
			out = append(out, mdRun{text: t})
		}
	}
	for s != "" {
		i := strings.IndexAny(s, "`*[")
		if i < 0 {
			plain(s)
			break
		}
		plain(s[:i])
		s = s[i:]
		switch {
		case s[0] == '`':
			if j := strings.IndexByte(s[1:], '`'); j >= 0 {
				out = append(out, mdRun{text: s[1 : j+1], style: &mdCode})
				s = s[j+2:]
				continue
			}
		case strings.HasPrefix(s, "**"):
			if j := strings.Index(s[2:], "**"); j >= 0 {
				out = append(out, mdRun{text: s[2 : j+2], style: &mdBold})
				s = s[j+4:]
				continue
			}
		case s[0] == '*':
			// *emphasis*, when it closes and is not a lone star in text.
			if j := strings.IndexByte(s[1:], '*'); j > 0 && s[1] != ' ' {
				out = append(out, mdRun{text: s[1 : j+1], style: &mdEm})
				s = s[j+2:]
				continue
			}
		case s[0] == '[':
			if j := strings.Index(s, "]("); j > 0 {
				if k := strings.IndexByte(s[j:], ')'); k > 0 {
					out = append(out, mdRun{text: s[1:j], link: s[j+2 : j+k]})
					s = s[j+k+1:]
					continue
				}
			}
		}
		plain(s[:1])
		s = s[1:]
	}
	return out
}

// wrapRuns lays styled runs out in lines of at most width columns: words
// are cut at spaces, a word keeping each part's own style.
func wrapRuns(runs []mdRun, width int, first, rest string) []docLine {
	type word struct{ plain, shown string }
	var words []word
	var plain, shown strings.Builder
	end := func() {
		if plain.Len() > 0 {
			words = append(words, word{plain.String(), shown.String()})
		}
		plain.Reset()
		shown.Reset()
	}
	for _, r := range runs {
		text := r.text
		if r.link != "" && strings.HasPrefix(r.link, "http") {
			text += " ‹" + r.link + "›"
		}
		for k, part := range strings.Split(text, " ") {
			if k > 0 {
				end()
			}
			if part == "" {
				continue
			}
			plain.WriteString(part)
			switch {
			case r.style != nil:
				shown.WriteString(r.style.Render(part))
			case r.link != "":
				shown.WriteString(mdLink.Render(part))
			default:
				shown.WriteString(part)
			}
		}
	}
	end()

	var out []docLine
	var line, lp strings.Builder
	start := func(pre string) {
		line.Reset()
		lp.Reset()
		line.WriteString(pre)
		lp.WriteString(pre)
	}
	start(first)
	col, empty := len([]rune(first)), true
	for _, w := range words {
		n := len([]rune(w.plain))
		if !empty && col+1+n > width {
			out = append(out, docLine{text: line.String(), plain: lp.String()})
			start(rest)
			col, empty = len([]rune(rest)), true
		}
		if !empty {
			line.WriteString(" ")
			lp.WriteString(" ")
			col++
		}
		line.WriteString(w.shown)
		lp.WriteString(w.plain)
		col += n
		empty = false
	}
	if !empty {
		out = append(out, docLine{text: line.String(), plain: lp.String()})
	}
	return out
}

// renderMarkdown lays a document out for a terminal width.
func renderMarkdown(src string, width int) []docLine {
	width = max(width, 30)
	var out []docLine
	blank := func() {
		if len(out) > 0 && out[len(out)-1].plain != "" {
			out = append(out, docLine{})
		}
	}
	lines := strings.Split(strings.ReplaceAll(src, "\r\n", "\n"), "\n")
	var para []string
	flush := func() {
		if len(para) > 0 {
			out = append(out, wrapRuns(inline(strings.Join(para, " ")), width, "", "")...)
			para = nil
		}
	}
	for i := 0; i < len(lines); i++ {
		l := lines[i]
		t := strings.TrimSpace(l)
		switch {
		case strings.HasPrefix(t, "```"):
			flush()
			blank()
			for i++; i < len(lines) && !strings.HasPrefix(strings.TrimSpace(lines[i]), "```"); i++ {
				code := "    " + strings.ReplaceAll(lines[i], "\t", "    ")
				out = append(out, docLine{text: mdCode.Render(truncateWidth(code, width)), plain: code})
			}
			blank()
		case t == "":
			flush()
			blank()
		case strings.HasPrefix(t, "#"):
			flush()
			level := len(t) - len(strings.TrimLeft(t, "#"))
			title := strings.TrimSpace(t[level:])
			plainTitle := ""
			for _, r := range inline(title) {
				plainTitle += r.text
			}
			style := mdH3
			switch level {
			case 1:
				style = mdH1
			case 2:
				style = mdH2
			}
			blank()
			out = append(out, docLine{text: style.Render(plainTitle), plain: plainTitle, heading: level})
			out = append(out, docLine{})
		case strings.HasPrefix(t, "|"):
			flush()
			var rows [][]string
			for ; i < len(lines) && strings.HasPrefix(strings.TrimSpace(lines[i]), "|"); i++ {
				cells := strings.Split(strings.Trim(strings.TrimSpace(lines[i]), "|"), "|")
				sep := true
				for j := range cells {
					cells[j] = strings.TrimSpace(cells[j])
					if strings.Trim(cells[j], ":-") != "" {
						sep = false
					}
				}
				if !sep {
					rows = append(rows, cells)
				}
			}
			i--
			out = append(out, renderTable(rows, width)...)
		case strings.HasPrefix(t, ">"):
			flush()
			q := strings.TrimSpace(strings.TrimPrefix(t, ">"))
			for _, d := range wrapRuns(inline(q), width-2, "", "") {
				out = append(out, docLine{text: sDim.Render("│ ") + d.text, plain: "│ " + d.plain})
			}
		case listItem(t) != "":
			flush()
			marker := listItem(t)
			indent := strings.Repeat(" ", len(l)-len(strings.TrimLeft(l, " ")))
			body := strings.TrimSpace(t[len(marker):])
			// The item's following lines, indented under it.
			for i+1 < len(lines) {
				nt := strings.TrimSpace(lines[i+1])
				if nt == "" || listItem(nt) != "" || strings.HasPrefix(nt, "```") || strings.HasPrefix(nt, "#") ||
					!strings.HasPrefix(lines[i+1], " ") {
					break
				}
				body += " " + nt
				i++
			}
			bullet := "• "
			if marker != "- " && marker != "* " {
				bullet = marker
			}
			out = append(out, wrapRuns(inline(body), width, indent+bullet, indent+strings.Repeat(" ", len([]rune(bullet))))...)
		default:
			para = append(para, t)
		}
	}
	flush()
	return out
}

func listItem(t string) string {
	if strings.HasPrefix(t, "- ") || strings.HasPrefix(t, "* ") {
		return t[:2]
	}
	for i, c := range t {
		if c >= '0' && c <= '9' {
			continue
		}
		if i > 0 && i < 4 && c == '.' && strings.HasPrefix(t[i+1:], " ") {
			return t[:i+2]
		}
		break
	}
	return ""
}

// renderTable aligns a markdown table, wrapping the widest column to fit.
func renderTable(rows [][]string, width int) []docLine {
	if len(rows) == 0 {
		return nil
	}
	plainCell := func(s string) string {
		var p string
		for _, r := range inline(s) {
			p += r.text
		}
		return p
	}
	n := 0
	for _, r := range rows {
		n = max(n, len(r))
	}
	w := make([]int, n)
	for _, r := range rows {
		for j, c := range r {
			w[j] = max(w[j], len([]rune(plainCell(c))))
		}
	}
	total := func() int {
		t := 0
		for _, x := range w {
			t += x + 2
		}
		return t
	}
	for total() > width {
		widest := 0
		for j := range w {
			if w[j] > w[widest] {
				widest = j
			}
		}
		if w[widest] <= 12 {
			break
		}
		w[widest]--
	}
	var out []docLine
	for ri, r := range rows {
		cols := make([][]string, n)
		height := 1
		for j := 0; j < n; j++ {
			c := ""
			if j < len(r) {
				c = plainCell(r[j])
			}
			cols[j] = strings.Split(wrap(c, max(w[j], 20), ""), "\n")
			if len([]rune(c)) <= w[j] {
				cols[j] = []string{c}
			}
			height = max(height, len(cols[j]))
		}
		for h := 0; h < height; h++ {
			var b strings.Builder
			for j := 0; j < n; j++ {
				c := ""
				if h < len(cols[j]) {
					c = cols[j][h]
				}
				b.WriteString(fmt.Sprintf("%-*s  ", w[j], truncate(c, w[j])))
			}
			plain := strings.TrimRight(b.String(), " ")
			text := plain
			if ri == 0 {
				text = mdBold.Render(plain)
			}
			out = append(out, docLine{text: text, plain: plain})
		}
	}
	return out
}

// --- the viewer ---

// docViewer is the manual: a list of topics, one open, its contents, and a
// search. Both the console and `llmgw docs` show it.
type docViewer struct {
	topics []docTopic
	open   int // the topic shown; -1 is the list
	sel    int // the topic chosen in the list
	scroll int
	query  string
	// toc and search are dialogs over the page.
	toc      *menuDialog
	tocLines []int
	asking   bool
	prompt   textField
	note     string
}

func newDocViewer() docViewer { return docViewer{topics: docTopics(), open: -1} }

func (v *docViewer) lines(width int) []docLine {
	if v.open < 0 {
		return nil
	}
	return renderMarkdown(v.topics[v.open].src(), width)
}

// key handles a key on an open page; false hands it back.
func (v *docViewer) key(k tea.KeyMsg, width, height int) bool {
	if v.asking {
		switch k.Type {
		case tea.KeyEsc:
			v.asking = false
		case tea.KeyEnter:
			v.asking = false
			v.query = strings.TrimSpace(v.prompt.Value())
			v.find(width, v.scroll, 1)
		default:
			v.prompt, _ = v.prompt.Update(k)
		}
		return true
	}
	if v.toc != nil {
		switch k.String() {
		case "up", "k":
			v.toc.sel = (v.toc.sel - 1 + len(v.toc.items)) % len(v.toc.items)
		case "down", "j", "tab":
			v.toc.sel = (v.toc.sel + 1) % len(v.toc.items)
		case "pgdown":
			v.toc.sel = min(len(v.toc.items)-1, v.toc.sel+10)
		case "pgup":
			v.toc.sel = max(0, v.toc.sel-10)
		case "enter":
			v.scroll = max(0, v.tocLines[v.toc.sel]-1)
			v.toc = nil
		case "esc", "q", "t":
			v.toc = nil
		}
		return true
	}
	if v.open < 0 {
		return false
	}
	n := len(v.lines(width))
	page := max(1, height-6)
	switch k.String() {
	case "up", "k":
		v.scroll--
	case "down", "j", "enter":
		v.scroll++
	case "pgdown", " ", "f":
		v.scroll += page
	case "pgup", "b":
		v.scroll -= page
	case "home", "g":
		v.scroll = 0
	case "end", "G":
		v.scroll = n - page
	case "t":
		v.openTOC(width)
	case "/":
		v.asking = true
		v.prompt = newTextField()
		v.prompt.Width = 30
		v.prompt.SetValue(v.query)
		v.prompt.Focus()
	case "n":
		// A match is shown two lines down; the next is after it.
		v.find(width, v.scroll+3, 1)
	case "N":
		v.find(width, v.scroll+1, -1)
	case "]":
		v.show(min(len(v.topics)-1, v.open+1))
	case "[":
		v.show(max(0, v.open-1))
	default:
		return false
	}
	v.scroll = max(0, min(v.scroll, n-1))
	return true
}

func (v *docViewer) show(i int) {
	v.open, v.sel, v.scroll, v.note = i, i, 0, ""
}

func (v *docViewer) openTOC(width int) {
	v.toc, v.tocLines = &menuDialog{title: "Contents · " + v.topics[v.open].title}, nil
	for i, l := range v.lines(width) {
		if l.heading == 0 || l.heading > 3 {
			continue
		}
		v.toc.items = append(v.toc.items, menuItem{label: strings.Repeat("  ", max(0, l.heading-1)) + truncate(l.plain, 60)})
		v.tocLines = append(v.tocLines, i)
		if i <= v.scroll+1 {
			v.toc.sel = len(v.tocLines) - 1
		}
	}
	if len(v.toc.items) == 0 {
		v.toc = nil
	}
}

// find moves to the next line holding the query, from line `from` in
// direction dir, wrapping round.
func (v *docViewer) find(width, from, dir int) {
	if v.query == "" {
		return
	}
	lines := v.lines(width)
	q := strings.ToLower(v.query)
	for k := 0; k < len(lines); k++ {
		i := ((from+k*dir)%len(lines) + len(lines)) % len(lines)
		if strings.Contains(strings.ToLower(lines[i].plain), q) {
			v.scroll = max(0, i-2)
			v.note = ""
			return
		}
	}
	v.note = "“" + v.query + "” is not in this page"
}

// body is the open page, the query's lines marked.
func (v *docViewer) body(width int) string {
	var b strings.Builder
	q := strings.ToLower(v.query)
	for _, l := range v.lines(width) {
		text := l.text
		if q != "" && strings.Contains(strings.ToLower(l.plain), q) {
			text = mdHit.Render(" ") + " " + text
		} else {
			text = "  " + text
		}
		b.WriteString(text + "\n")
	}
	return b.String()
}

// list is the topics, as a table.
func (v *docViewer) list(width int, focused bool) string {
	var rows [][]string
	for _, t := range v.topics {
		rows = append(rows, []string{t.title, sDim.Render("llmgw docs " + t.key)})
	}
	return "\n  " + sDim.Render("Everything there is to read about llmgw, carried in the binary.") + "\n\n" +
		table([]string{"TOPIC", "ALSO"}, rows, v.sel, width, focused)
}

// dialog is the contents or the search, open over the page.
func (v *docViewer) dialog() (string, string) {
	switch {
	case v.asking:
		return "Find in this page", v.prompt.View() + "\n\n" + sDim.Render("Enter · then n next, N back · Esc cancel")
	case v.toc != nil:
		d := consoleModel{menuD: v.toc, height: 40}
		_, body := d.actionDialog()
		return v.toc.title, body
	case v.note != "":
		return "", ""
	}
	return "", ""
}

const docKeys = "↑↓ PgUp/PgDn g/G scroll · T contents · / find · n/N next · [ ] topic · ← back"

// --- `llmgw docs` ---

type docsModel struct {
	v             docViewer
	width, height int
	inPage        bool
}

func (m docsModel) Init() tea.Cmd { return nil }

func (m docsModel) pageWidth() int { return max(30, m.width-navWidth-10) }

func (m docsModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		m.width, m.height = msg.Width, msg.Height
	case tea.KeyMsg:
		if msg.Type == tea.KeyCtrlC {
			return m, tea.Quit
		}
		if m.inPage && m.v.key(msg, m.pageWidth(), m.height) {
			return m, nil
		}
		switch msg.String() {
		case "q":
			return m, tea.Quit
		case "up", "k":
			if !m.inPage {
				m.v.sel = (m.v.sel - 1 + len(m.v.topics)) % len(m.v.topics)
				m.v.show(m.v.sel)
			}
		case "down", "j":
			if !m.inPage {
				m.v.sel = (m.v.sel + 1) % len(m.v.topics)
				m.v.show(m.v.sel)
			}
		case "enter", "right", "l", "tab":
			m.inPage = true
		case "esc", "left", "h", "backspace":
			if m.inPage {
				m.inPage = false
			} else {
				return m, tea.Quit
			}
		}
	}
	return m, nil
}

func (m docsModel) View() string {
	var nav []navItem
	for i, t := range m.v.topics {
		nav = append(nav, navItem{Label: t.title, Current: i == m.v.open})
	}
	keys := "↑↓ topic · → or Enter read · Q leave"
	if m.inPage {
		keys = docKeys
	}
	if m.v.note != "" {
		keys = m.v.note
	}
	f := frame{Width: m.width, Height: m.height, Title: "llmgw manual", Where: "llmgw docs",
		Nav: nav, PanelTitle: m.v.topics[m.v.open].title, Body: "\n" + m.v.body(m.pageWidth()),
		Scroll: m.v.scroll, Keys: keys}
	f.DialogTitle, f.Dialog = m.v.dialog()
	return f.render()
}

func newDocsCmd() *cobra.Command {
	return &cobra.Command{
		Use:   "docs [TOPIC]",
		Short: "Read the manual: every document, and a page for every command",
		Long: "In a terminal, a reader like info: the topics down the left, the page on\n" +
			"the right, T for its contents, / to find. Piped, the topic's text, or the\n" +
			"list of topics. TOPIC is a name from that list or a word of its title.",
		Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			v := newDocViewer()
			i := 0
			if len(args) == 1 {
				if i = findTopic(v.topics, args[0]); i < 0 {
					return fmt.Errorf("no topic %q; `llmgw docs` lists them", args[0])
				}
			}
			out := cmd.OutOrStdout()
			if !interactive(cmd) {
				if len(args) == 0 {
					for _, t := range v.topics {
						fmt.Fprintf(out, "%-26s %s\n", t.key, t.title)
					}
					return nil
				}
				_, err := fmt.Fprint(out, v.topics[i].src())
				return err
			}
			v.show(i)
			m := docsModel{v: v, width: 100, height: 30, inPage: len(args) == 1}
			_, err := tea.NewProgram(m, tea.WithOutput(out), tea.WithAltScreen()).Run()
			return err
		},
	}
}