package main

// The invite view: a window you fill in to make an event.
//
//	cal9 -v invite [calendar]
//
// It writes the calendar's new file in the tree's own key: value form,
// so nothing here knows what iCalendar looks like -- calfs composes it,
// and a comma in a summary stays a comma. With attendees on a backend
// that schedules, writing the file is also sending the invitation.

import (
	"fmt"
	"os"
	"os/exec"
	"path"
	"strings"

	"time"

	"9front/gui/draw"
	"9front/gui/ui"
)

type form struct {
	cal    string
	fields []*ui.Field
	focus  int
	note   string // what happened, shown under the buttons
}

func newForm(cal string) *form {
	return &form{
		cal: cal,
		fields: []*ui.Field{
			{Label: "summary"},
			{Label: "when"},
			{Label: "minutes", Value: "30"},
			{Label: "where"},
			{Label: "attendees"},
		},
	}
}

func (s *state) drawInvite(r draw.Rectangle) {
	s.Fill(r, "bg")
	f := s.form
	lh := int32(s.F.Height) + 8

	y := r.Min.Y + pad
	s.Text(draw.Point{X: r.Min.X + pad, Y: y}, "ink", "new event on "+f.cal)
	y += lh

	for i, fl := range f.fields {
		w := r.Max.X - pad
		// the when field gets a button that opens the picker
		if fl.Label == "when" {
			bw := s.F.Width("pick") + 20
			w -= bw + 6
			s.Button(draw.Rect(w+6, y, w+6+bw, y+lh-4), "pick", false, s.pickWhen)
		}
		s.Draw(fl, draw.Rect(r.Min.X+pad, y, w, y+lh-4), i == f.focus)
		n := i
		s.On(fl.R, func() { f.focus = n; s.redraw() })
		y += lh
	}

	y += 6
	x := r.Min.X + pad
	for _, b := range []struct {
		label string
		do    func()
	}{
		{"Create", func() { s.create() }},
		{"Clear", func() {
			for _, fl := range f.fields {
				fl.Value = ""
			}
			f.fields[2].Value = "30"
			f.note = ""
			s.redraw()
		}},
	} {
		do := b.do
		bw := s.F.Width(b.label) + 20
		br := draw.Rect(x, y, x+bw, y+lh)
		s.Button(br, b.label, false, do)
		x = br.Max.X + 6
	}
	y += lh + 6

	if f.note != "" {
		s.Text(draw.Point{X: r.Min.X + pad, Y: y}, "ink", s.Fit(f.note, r.Dx()-pad*2))
		y += lh
	}
	s.Text(draw.Point{X: r.Min.X + pad, Y: r.Max.Y - int32(s.F.Height) - pad}, "rule",
		"tab moves, ^U clears a field, when: 2026-08-28 15:00")
	s.D.Flush()
}

// pickWhen opens datepick in a window of its own and waits for it.
//
// A window started through wctl has nowhere useful to print -- nothing
// is reading its standard output -- so datepick is asked to leave the
// answer in a file, and a goroutine watches for it. That keeps the form
// answering the mouse while the picker is up.
func (s *state) pickWhen() {
	tmp := fmt.Sprintf("/tmp/cal9.pick.%d", os.Getpid())
	os.Remove(tmp)
	s.New(360, 320, "datepick", "-t", "-o", tmp)
	go func() {
		for i := 0; i < 600; i++ { // two minutes is long enough to choose
			if b, err := os.ReadFile(tmp); err == nil && len(b) > 0 {
				os.Remove(tmp)
				s.picked <- strings.TrimSpace(string(b))
				return
			}
			time.Sleep(200 * time.Millisecond)
		}
	}()
}

// create writes the form to the calendar's new file. The fs composes
// the icalendar; this only has to say what it means.
func (s *state) create() {
	f := s.form
	get := func(i int) string { return strings.TrimSpace(f.fields[i].Value) }

	if get(0) == "" || get(1) == "" {
		f.note = "summary and when are needed"
		s.redraw()
		return
	}
	start, err := seconds(get(1))
	if err != nil {
		f.note = "cannot read the time: " + get(1)
		s.redraw()
		return
	}
	mins := int64(30)
	fmt.Sscan(get(2), &mins)
	if mins <= 0 {
		mins = 30
	}

	var b strings.Builder
	fmt.Fprintf(&b, "summary: %s\n", get(0))
	fmt.Fprintf(&b, "start: %d\n", start)
	fmt.Fprintf(&b, "end: %d\n", start+mins*60)
	if v := get(3); v != "" {
		fmt.Fprintf(&b, "location: %s\n", v)
	}
	if v := get(4); v != "" {
		me := calMe(path.Join(mtpt, "calendars", f.cal))
		if me == "" {
			f.note = f.cal + " has no me=; cannot say who is organising"
			s.redraw()
			return
		}
		fmt.Fprintf(&b, "organizer: %s\n", me)
		for _, a := range strings.FieldsFunc(v, func(r rune) bool {
			return r == ',' || r == ' '
		}) {
			fmt.Fprintf(&b, "attendee: %s\n", a)
		}
	}

	nw := path.Join(mtpt, "calendars", f.cal, "new")
	fd, err := os.OpenFile(nw, os.O_WRONLY, 0)
	if err != nil {
		f.note = err.Error()
		s.redraw()
		return
	}
	_, err = fd.WriteString(b.String())
	if cerr := fd.Close(); err == nil {
		err = cerr
	}
	if err != nil {
		f.note = err.Error()
	} else {
		f.note = "created: " + get(0)
		for _, fl := range f.fields {
			fl.Value = ""
		}
		f.fields[2].Value = "30"
	}
	s.redraw()
}

// calMe reads whose calendar this is, the same line pim/invite reads.
func calMe(dir string) string {
	b, err := os.ReadFile(path.Join(dir, "ctl"))
	if err != nil {
		return ""
	}
	for _, l := range strings.Split(string(b), "\n") {
		if v, ok := strings.CutPrefix(l, "me "); ok {
			if i := strings.IndexByte(v, ','); i >= 0 {
				v = v[:i]
			}
			return strings.TrimSpace(v)
		}
	}
	return ""
}

// writable names the calendars that can take a new event.
func writable() []string {
	var out []string
	for _, c := range calendars() {
		b, err := os.ReadFile(path.Join(mtpt, "calendars", c, "ctl"))
		if err != nil {
			continue
		}
		for _, l := range strings.Split(string(b), "\n") {
			if v, ok := strings.CutPrefix(l, "caps "); ok {
				for _, f := range strings.Fields(v) {
					if f == "write" {
						out = append(out, c)
					}
				}
			}
		}
	}
	return out
}

// seconds parses a human date the way seconds(1) does, by asking it.
// Reimplementing tmparse here would be a second answer to a question
// the system already answers.
func seconds(when string) (int64, error) {
	out, err := exec.Command("/bin/seconds", when).Output()
	if err != nil {
		return 0, err
	}
	var n int64
	if _, err := fmt.Sscan(strings.TrimSpace(string(out)), &n); err != nil {
		return 0, err
	}
	return n, nil
}