DEV-1313: Add additional map types (#76)

* add helper to draw a ring of hazards

* refactor tests to not be internal tests

* add "hz_inner_wall" map

* add "hz_rings" map

* fix map registry

* fix: edge case bugs in drawRing

* remove println

* add "hz_columns"

* add "hz_rivers_bridges" map

* WIP: implementing spiral hazards map

* finish basic testing of 'hz_spiral'

* include first turn

* add "hz_hazards" map

* remove incorrect author

* add "hz_grow_box" map

* add "hz_expand_box" map

* add "hz_expand_scatter" map

* remove debug

* document the new "Range" method

* - use rules.RulesetError instead of generic error
- use a rules.Point for map rivers and bridgets map key

* use rules.RulesetError instead of errors.New

* provide more detail about boundar conditions

* fix documentation (max can be == min)

* add unit tests

maps/helpers.go

@@ -1,6 +1,8 @@
 package maps
 
-import "github.com/BattlesnakeOfficial/rules"
+import (
+	"github.com/BattlesnakeOfficial/rules"
+)
 
 // SetupBoard is a shortcut for looking up a map by ID and initializing a new board state with it.
 func SetupBoard(mapID string, settings rules.Settings, width, height int, snakeIDs []string) (*rules.BoardState, error) {
@@ -87,3 +89,91 @@ func (m StubMap) UpdateBoard(previousBoardState *rules.BoardState, settings rule
 	}
 	return nil
 }
+
+// drawRing draws a ring of hazard points offset from the outer edge of the board
+func drawRing(bw, bh, hOffset, vOffset int) ([]rules.Point, error) {
+	if bw < 1 {
+		return nil, rules.RulesetError("board width too small")
+	}
+
+	if bh < 1 {
+		return nil, rules.RulesetError("board height too small")
+	}
+
+	if hOffset >= bw-1 {
+		return nil, rules.RulesetError("horizontal offset too large")
+	}
+
+	if vOffset >= bh-1 {
+		return nil, rules.RulesetError("vertical offset too large")
+	}
+
+	if hOffset < 1 {
+		return nil, rules.RulesetError("horizontal offset too small")
+	}
+
+	if vOffset < 1 {
+		return nil, rules.RulesetError("vertical offset too small")
+	}
+
+	// calculate the start/end point of the horizontal borders
+	xStart := hOffset - 1
+	xEnd := bw - hOffset
+
+	// calculate start/end point of the vertical borders
+	yStart := vOffset - 1
+	yEnd := bh - vOffset
+
+	// we can pre-determine how many points will be in the ring and allocate a slice of exactly that size
+	numPoints := 2 * (xEnd - xStart + 1) // horizontal hazard points
+
+	// Add vertical walls, if there are any.
+	// Sometimes there are no vertical walls when the ring height is only 2.
+	// In that case, the vertical walls are handled by the horizontal walls
+	if yEnd >= yStart {
+		numPoints += 2*(yEnd-yStart+1) - 4
+	}
+
+	hazards := make([]rules.Point, 0, numPoints)
+
+	// draw horizontal walls
+	for x := xStart; x <= xEnd; x++ {
+		hazards = append(hazards,
+			rules.Point{X: x, Y: yStart},
+			rules.Point{X: x, Y: yEnd},
+		)
+	}
+
+	// draw vertical walls, but don't include corners that the horizontal walls already included
+	for y := yStart + 1; y <= yEnd-1; y++ {
+		hazards = append(hazards,
+			rules.Point{X: xStart, Y: y},
+			rules.Point{X: xEnd, Y: y},
+		)
+	}
+
+	return hazards, nil
+}
+
+func maxInt(n1 int, n ...int) int {
+	max := n1
+	for _, v := range n {
+		if v > max {
+			max = v
+		}
+	}
+
+	return max
+}
+
+func isOnBoard(w, h, x, y int) bool {
+	if x >= w || x < 0 {
+		return false
+	}
+
+	if y >= h || y < 0 {
+		return false
+	}
+
+	return true
+}