// Package ui is the bits every program drawing in a rio window needs
// and none of them should write twice: borders, buttons, a button-3
// menu, hit regions, dragging the window about, selecting text.
//
// It is a kit, not a framework. Every function draws a thing and, where
// it makes sense, records where it was drawn so a click can find it.
// The program keeps its own event loop and its own idea of what to
// redraw; nothing here calls back into it except the handler you give.
package ui

import (
	"os"
	"fmt"

	"9front/gui/draw"
)

// UI is what the drawing functions need: somewhere to draw, something
// to draw with, and a palette. A program embeds it.
type UI struct {
	D   *draw.Display
	Win *draw.Image
	F   *draw.Font
	Col map[string]*draw.Image

	hits []Hit
}

// A Hit is a region that does something when clicked.
type Hit struct {
	R  draw.Rectangle
	Do func()
}

// Reset forgets every hit region. Call it at the top of a redraw, or
// clicks will find things that are no longer on the screen.
func (u *UI) Reset() { u.hits = u.hits[:0] }

// On records a region. The first one that contains a point wins, so
// record the small things before the big ones that enclose them.
func (u *UI) On(r draw.Rectangle, do func()) {
	u.hits = append(u.hits, Hit{r, do})
}

// Click runs the handler for the first region containing p, and says
// whether it found one.
func (u *UI) Click(p draw.Point) bool {
	for _, h := range u.hits {
		if In(h.R, p) {
			h.Do()
			return true
		}
	}
	return false
}

// In reports whether p is inside r.
func In(r draw.Rectangle, p draw.Point) bool {
	return p.X >= r.Min.X && p.X < r.Max.X && p.Y >= r.Min.Y && p.Y < r.Max.Y
}

// ---------------------------------------------------------------- paint

// Border width rio leaves around a window. rio draws the border into
// the client's own image and colours it to show which window has the
// input, so a program that fills its whole rectangle erases it and the
// window loses its edge. Draw inside Body and those pixels stay rio's.
const Selborder = 4

// Body is the part of the window a program should draw in: everything
// but rio's border.
func (u *UI) Body() draw.Rectangle {
	r := u.Win.Rect()
	return draw.Rect(r.Min.X+Selborder, r.Min.Y+Selborder,
		r.Max.X-Selborder, r.Max.Y-Selborder)
}

// Fill paints a rectangle in a named colour.
func (u *UI) Fill(r draw.Rectangle, c string) {
	if img, ok := u.Col[c]; ok {
		draw.Draw(u.Win, r, img, nil, draw.ZP)
	}
}

// Text draws a string at p in a named colour.
func (u *UI) Text(p draw.Point, c string, s string) {
	if img, ok := u.Col[c]; ok {
		u.F.String(u.Win, p, img, s)
	}
}

// Border outlines a rectangle, one pixel wide. Everything that draws a
// box wants this, and everything used to write it out four times.
func (u *UI) Border(r draw.Rectangle, c string) {
	u.Fill(draw.Rect(r.Min.X, r.Min.Y, r.Max.X, r.Min.Y+1), c)
	u.Fill(draw.Rect(r.Min.X, r.Max.Y-1, r.Max.X, r.Max.Y), c)
	u.Fill(draw.Rect(r.Min.X, r.Min.Y, r.Min.X+1, r.Max.Y), c)
	u.Fill(draw.Rect(r.Max.X-1, r.Min.Y, r.Max.X, r.Max.Y), c)
}

// Button draws a labelled box and records it. on picks the lit
// background, for a button that shows the current state.
func (u *UI) Button(r draw.Rectangle, label string, on bool, do func()) {
	bg := "tag"
	if on {
		bg = "today"
	}
	u.Fill(r, bg)
	u.Border(r, "border")
	w := u.F.Width(label)
	u.Text(draw.Point{X: r.Min.X + (r.Dx()-w)/2, Y: r.Min.Y + 3}, "ink", label)
	u.On(r, do)
}

// Fit truncates s to w pixels, so a long summary cannot run out of its
// box and over whatever is next to it.
func (u *UI) Fit(s string, w int32) string {
	if u.F.Width(s) <= w {
		return s
	}
	r := []rune(s)
	for len(r) > 1 {
		r = r[:len(r)-1]
		if u.F.Width(string(r)+"...") <= w {
			return string(r) + "..."
		}
	}
	return ""
}

// Wrap breaks text into lines no wider than w.
func (u *UI) Wrap(text string, w int32) []string {
	var out []string
	line := ""
	for _, word := range fields(text) {
		try := word
		if line != "" {
			try = line + " " + word
		}
		if u.F.Width(try) <= w || line == "" {
			line = try
			continue
		}
		out = append(out, line)
		line = word
	}
	if line != "" {
		out = append(out, line)
	}
	return out
}

func fields(s string) []string {
	var out []string
	cur := ""
	for _, r := range s {
		if r == ' ' || r == '\t' || r == '\n' {
			if cur != "" {
				out = append(out, cur)
				cur = ""
			}
			continue
		}
		cur += string(r)
	}
	if cur != "" {
		out = append(out, cur)
	}
	return out
}

// ---------------------------------------------------------------- rio

// Wctl asks rio to do something to our window: resize, move, hide.
// Outside rio there is no /dev/wctl and this quietly does nothing,
// which is the right answer for a menu item that cannot apply.
func (u *UI) Wctl(cmd string) {
	f, err := os.OpenFile("/dev/wctl", os.O_WRONLY, 0)
	if err != nil {
		return
	}
	defer f.Close()
	fmt.Fprint(f, cmd)
}

// Resize asks rio for a window of a given size, keeping the corner.
func (u *UI) Resize(dx, dy int32) {
	r := u.Win.Rect()
	u.Wctl(fmt.Sprintf("resize -r %d %d %d %d",
		r.Min.X, r.Min.Y, r.Min.X+dx, r.Min.Y+dy))
}


// Hide puts the window away.
func (u *UI) Hide() { u.Wctl("hide") }

// New starts a command in a window of its own.
//
// rio splits this line on spaces and there is no quoting, so every
// argument has to be a single token.
func (u *UI) New(dx, dy int32, argv ...string) {
	cmd := fmt.Sprintf("new -dx %d -dy %d", dx, dy)
	for _, a := range argv {
		cmd += " " + a
	}
	u.Wctl(cmd)
}