98 lines
2.6 KiB
Go
98 lines
2.6 KiB
Go
// Package edge provides a model and methods for representing and manipulating edges.
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package edge
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import (
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"math"
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"github.com/StevanFreeborn/advent-of-code-2025/cmd/09/rectangle"
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"github.com/StevanFreeborn/advent-of-code-2025/internal/position"
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)
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type Edge interface {
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Start() position.Position
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End() position.Position
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VerticallyContains(position.Position) bool
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IntersectsHorizontalLineAt(position.Position) bool
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Intersects(rect rectangle.Rectangle) bool
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}
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type edge struct {
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start position.Position
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end position.Position
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totalHeight int
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totalWidth int
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minRow float64
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maxRow float64
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minColumn float64
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maxColumn float64
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}
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func From(start position.Position, end position.Position) Edge {
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totalHeight := int(math.Abs(float64(end.Row() - start.Row())))
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totalWidth := int(math.Abs(float64(end.Column() - start.Column())))
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minRow := math.Min(float64(start.Row()), float64(end.Row()))
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maxRow := math.Max(float64(start.Row()), float64(end.Row()))
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minColumn := math.Min(float64(start.Column()), float64(end.Column()))
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maxColumn := math.Max(float64(start.Column()), float64(end.Column()))
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return edge{
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start: start,
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end: end,
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totalHeight: totalHeight,
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totalWidth: totalWidth,
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minRow: minRow,
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maxRow: maxRow,
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minColumn: minColumn,
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maxColumn: maxColumn,
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}
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}
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func (e edge) Start() position.Position {
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return e.start
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}
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func (e edge) End() position.Position {
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return e.end
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}
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func (e edge) VerticallyContains(p position.Position) bool {
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return (e.start.Row() <= p.Row()) && (p.Row() <= e.end.Row())
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}
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func (e edge) IntersectsHorizontalLineAt(p position.Position) bool {
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centerPercentageOfEdgeHeight := int(float64(p.Row()-e.start.Row()) / float64(e.totalHeight))
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edgeColumnAtCenterRow := e.start.Column() + centerPercentageOfEdgeHeight*e.totalWidth
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return p.Row() <= edgeColumnAtCenterRow
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}
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func (e edge) Intersects(rect rectangle.Rectangle) bool {
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isVerticalEdge := e.start.Column() == e.end.Column()
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if isVerticalEdge {
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isRectBetweenEdgeColumns := e.start.Column() > rect.MinColumn() && e.start.Column() < rect.MaxColumn()
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if isRectBetweenEdgeColumns {
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overlapStart := int(math.Max(e.minRow, float64(rect.MinRow())))
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overlapEnd := int(math.Min(e.maxRow, float64(rect.MaxRow())))
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if overlapEnd > overlapStart {
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return true
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}
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}
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} else {
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isRectBetweenEdgeRows := e.start.Row() > rect.MinRow() && e.start.Row() < rect.MaxRow()
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if isRectBetweenEdgeRows {
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overlapStart := int(math.Max(e.minColumn, float64(rect.MinColumn())))
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overlapEnd := int(math.Min(e.maxColumn, float64(rect.MaxColumn())))
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if overlapEnd > overlapStart {
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return true
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}
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}
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}
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return false
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}
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