package termui

import (
	"unicode/utf8"
)

type Tab struct {
    Label   string
	RuneLen int
    Blocks  []Bufferer
}

func NewTab(label string) *Tab {
    return &Tab {
                Label:  label,
				RuneLen: utf8.RuneCount([]byte(label)) }
}

func (tab *Tab) AddBlocks(rs ...Bufferer) {
    for _, r := range rs {
        tab.Blocks = append(tab.Blocks, r)
    }
}

func (tab *Tab) Buffer() []Point {
    points := []Point{}
    for blockNum := 0; blockNum < len(tab.Blocks); blockNum++ {
        b := &tab.Blocks[blockNum]
        blockPoints := (*b).Buffer()
        points = append(points, blockPoints...)
    }
    return points
}

type Tabpane struct {
    Block
    Tabs			[]Tab
    activeTabIndex	int
	posTabText		[]int
	offTabText		int
}

func NewTabpane() *Tabpane {
	tp := Tabpane {
		Block:			*NewBlock(),
		activeTabIndex: 0,
		offTabText:		0}
	return &tp
}

func (tp *Tabpane) SetTabs(tabs ...Tab) {
	tp.Tabs = make([]Tab, len(tabs))
	tp.posTabText = make([]int, len(tabs)+1)
	off := 0
	for i :=0; i < len(tp.Tabs); i++ {
		tp.Tabs[i] = tabs[i]
		tp.posTabText[i] = off
		off += tp.Tabs[i].RuneLen+1 //+1 for space between tabs
	}
	tp.posTabText[len(tabs)] = off-1 //total length of Tab's text
}

func (tp *Tabpane) SetActiveLeft() {
	if tp.activeTabIndex == 0 {
		return
	}
    tp.activeTabIndex -= 1
	if tp.posTabText[tp.activeTabIndex] < tp.offTabText {
		tp.offTabText = tp.posTabText[tp.activeTabIndex]
	}
}

func (tp *Tabpane) SetActiveRight() {
	if tp.activeTabIndex == len(tp.Tabs)-1 {
		return
	}
    tp.activeTabIndex += 1
	endOffset := tp.posTabText[tp.activeTabIndex] + tp.Tabs[tp.activeTabIndex].RuneLen
	if endOffset + tp.offTabText > tp.innerWidth {
		tp.offTabText = endOffset - tp.innerWidth
	}
}

// Checks if left and right tabs are fully visible
// if only left tabs are not visible return -1
// if only right tabs are not visible return 1
// if both return 0
// use only if fitsWidth() returns false
func (tp *Tabpane) checkAlignment() int {
	ret := 0
	if tp.offTabText > 0 {
		ret = -1
	}
	if tp.offTabText + tp.innerWidth < tp.posTabText[len(tp.Tabs)] {
		ret += 1
	}
	return ret
}

// Checks if all tabs fits innerWidth of Tabpane
func (tp *Tabpane) fitsWidth() bool {
	return tp.innerWidth >= tp.posTabText[len(tp.Tabs)]
}

func (tp *Tabpane) align() {
	if !tp.fitsWidth() && !tp.HasBorder {
		tp.innerWidth -= 2
		tp.innerX += 1
	}
}

// Adds the point only if it is visible in Tabpane.
// Point can be invisible if concatenation of Tab's texts is widther then
// innerWidth of Tabpane
func (tp *Tabpane) addPoint(ptab []Point, charOffset *int, oftX *int, points ...Point) []Point {
	if *charOffset < tp.offTabText || tp.offTabText + tp.innerWidth < *charOffset {
		*charOffset++
		return ptab
	}
	for _, p := range(points) {
		p.X = *oftX
		ptab = append(ptab, p)
	}
	*oftX++
	*charOffset++
	return ptab
}

// Draws the point and redraws upper and lower border points (if it has one)
func (tp *Tabpane) drawPointWithBorder(p Point, ch rune, chbord rune, chdown rune, chup rune) []Point {
	var addp []Point
	p.Ch = ch
	if tp.HasBorder {
		p.Ch = chdown
		p.Y = tp.innerY-1
		addp = append(addp, p)
		p.Ch = chup
		p.Y = tp.innerY+1
		addp = append(addp, p)
		p.Ch = chbord
	}
	p.Y = tp.innerY
	return append(addp, p)
}

func (tp *Tabpane) Buffer() []Point {
	if tp.HasBorder {
		tp.Height = 3
	} else {
		tp.Height = 1
	}
	if tp.Width > tp.posTabText[len(tp.Tabs)]+2 {
		tp.Width = tp.posTabText[len(tp.Tabs)]+2
	}
    ps := tp.Block.Buffer()
	tp.align()
	if tp.innerHeight <= 0 || tp.innerWidth <= 0 {
		return nil
	}
	oftX := tp.innerX
	charOffset := 0
	pt := Point{Bg: tp.Border.BgColor, Fg: tp.Border.FgColor}
	for i, tab := range tp.Tabs {

		if i != 0 {
			pt.X = oftX
			pt.Y = tp.innerY
			addp := tp.drawPointWithBorder(pt, ' ', VERTICAL_LINE, HORIZONTAL_DOWN, HORIZONTAL_UP)
			ps = tp.addPoint(ps, &charOffset, &oftX, addp...)
		}

		if i == tp.activeTabIndex {
			pt.Bg = theme.TabActiveBg
		}
		rs := str2runes(tab.Label)
		for k := 0; k < len(rs); k++ {

			addp := make([]Point, 0, 2)
            if i == tp.activeTabIndex && tp.HasBorder {
				pt.Ch = ' '
				pt.Y = tp.innerY + 1
				pt.Bg = tp.Border.BgColor
				addp = append(addp, pt)
				pt.Bg = theme.TabActiveBg
			}

			pt.Y = tp.innerY
			pt.Ch = rs[k]

			addp = append(addp, pt)
			ps = tp.addPoint(ps, &charOffset, &oftX, addp...)
		}
		pt.Bg = tp.Border.BgColor

		if !tp.fitsWidth() {
			all := tp.checkAlignment()
			pt.X = tp.innerX-1

			pt.Ch = '*'
			if tp.HasBorder {
				pt.Ch = VERTICAL_LINE
			}
			ps = append(ps, pt)

			if all <= 0 {
				addp := tp.drawPointWithBorder(pt, '<', '«', HORIZONTAL_LINE, HORIZONTAL_LINE)
				ps = append(ps, addp...)
			}

			pt.X = tp.innerX + tp.innerWidth
			pt.Ch = '*'
			if tp.HasBorder {
				pt.Ch = VERTICAL_LINE
			}
			ps = append(ps, pt)
			if all >= 0 {
				addp := tp.drawPointWithBorder(pt, '>', '»', HORIZONTAL_LINE, HORIZONTAL_LINE)
				ps = append(ps, addp...)
			}
		}

		//draw tab content below the Tabpane
        if i == tp.activeTabIndex {
            blockPoints := tab.Buffer()
			for i := 0; i < len(blockPoints); i++ {
				blockPoints[i].Y += tp.Height + tp.Y
			}
			ps = append(ps, blockPoints...)
		}
	}

	return ps
}