package layouts

import "image"
import "golang.org/x/image/math/fixed"
import "git.tebibyte.media/sashakoshka/tomo"
import "git.tebibyte.media/sashakoshka/tomo/artist"
import "git.tebibyte.media/sashakoshka/tomo/fixedutil"

// Vertical arranges elements vertically. Elements at the start of the entry
// list will be positioned at the top, and elements at the end of the entry list
// will positioned at the bottom. All elements have the same width.
type Vertical struct {
	// If Gap is true, a gap will be placed between each element.
	Gap bool

	// If Pad is true, there will be padding running along the inside of the
	// layout's border.
	Pad bool
}

// Arrange arranges a list of entries vertically.
func (layout Vertical) Arrange (
	entries []tomo.LayoutEntry,
	margin  image.Point,
	padding artist.Inset,
	bounds image.Rectangle,
) {
	if layout.Pad { bounds = padding.Apply(bounds) }
	
	// get height  of expanding elements
	expandingElementHeight, minimumHeights := layout.expandingElementHeight (
		entries, margin, padding, bounds.Dy())

	// set the size and position of each element
	dot := fixedutil.Pt(bounds.Min)
	for index, entry := range entries {
		if index > 0 && layout.Gap { dot.Y += fixed.I(margin.Y) }
		
		entry.Bounds.Min = fixedutil.FloorPt(dot)
		entryHeight := fixed.Int26_6(0)
		if entry.Expand {
			entryHeight = expandingElementHeight
		} else {
			entryHeight = fixed.I(minimumHeights[index])
		}
		dot.Y += entryHeight
		entryBounds := entry.Bounds
		entry.Bounds.Max = entryBounds.Min.Add (
			image.Pt(bounds.Dx(),
			entryHeight.Floor()))
		entries[index] = entry
	}
}

// MinimumSize returns the minimum width and height that will be needed to
// arrange the given list of entries.
func (layout Vertical) MinimumSize (
	entries []tomo.LayoutEntry,
	margin  image.Point,
	padding artist.Inset,
) (
	width, height int,
) {
	for index, entry := range entries {
		entryWidth, entryHeight := entry.MinimumSize()
		if entryWidth > width {
			width = entryWidth
		}
		height += entryHeight
		if layout.Gap && index > 0 {
			height += margin.Y
		}
	}

	if layout.Pad {
		width  += padding.Horizontal()
		height += padding.Vertical()
	}
	return
}

func (layout Vertical) expandingElementHeight (
	entries []tomo.LayoutEntry,
	margin  image.Point,
	padding artist.Inset,
	freeSpace int,
) (
	height fixed.Int26_6,
	minimumHeights []int,
) {
	// count the number of expanding elements and the amount of free space
	// for them to collectively occupy, while gathering minimum heights.
	minimumHeights = make([]int, len(entries))
	expandingElements := 0
	for index, entry := range entries {
		_, entryMinHeight := entry.MinimumSize()
		minimumHeights[index] = entryMinHeight
		
		if entry.Expand {
			expandingElements ++
		} else {
			freeSpace -= entryMinHeight
		}
		if index > 0 && layout.Gap {
			freeSpace -= margin.Y
		}
	}
	
	if expandingElements > 0 {
		height = fixed.I(freeSpace) / fixed.Int26_6(expandingElements)
	}
	return
}