Decompose fireBolt (refactor step 7)

The fire_bolt loop splits into boltDirChar, boltBounces,
boltStrikesMonster, and boltStrikesHero; loop state (hitHero/changed/
used) stays in fireBolt. Effect order and RNG calls unchanged.

game/sticks.go

@@ -326,21 +326,7 @@ func (g *RogueGame) fireBolt(start Coord, dir *Coord, name string) {
 	bolt.DPlus = 0
 	g.Items.Weapons[WeaponFlame].Name = name
 
-	var dirch byte
+	dirch := boltDirChar(*dir)
-
-	switch dir.Y + dir.X {
-	case 0:
-		dirch = '/'
-	case 1, -1:
-		if dir.Y == 0 {
-			dirch = '-'
-		} else {
-			dirch = '|'
-		}
-	case 2, -2:
-		dirch = '\\'
-	}
-
 	pos := start
 	hitHero := !fromHero
 	used := false
@@ -351,22 +337,9 @@ func (g *RogueGame) fireBolt(start Coord, dir *Coord, name string) {
 		pos.Y += dir.Y
 		pos.X += dir.X
 		spotpos = append(spotpos, pos)
+
 		ch := g.Level.VisibleChar(pos.Y, pos.X)
-		bounce := false
+		if boltBounces(ch, p.Pos, pos) {
-
-		switch ch {
-		case Door:
-			// this code is necessary if the hero is on a door and he
-			// fires at the wall the door is in, it would otherwise loop
-			// infinitely
-			if p.Pos != pos {
-				bounce = true
-			}
-		case '|', '-', ' ':
-			bounce = true
-		}
-
-		if bounce {
 			if !changed {
 				hitHero = !hitHero
 			}
@@ -384,57 +357,11 @@ func (g *RogueGame) fireBolt(start Coord, dir *Coord, name string) {
 		if tp := g.Level.MonsterAt(pos.Y, pos.X); !hitHero && tp != nil {
 			hitHero = true
 			changed = !changed
-
+			used = g.boltStrikesMonster(tp, bolt, pos, ch, name, fromHero)
-			tp.OldCh = g.Level.Char(pos.Y, pos.X)
-			if !g.saveThrow(VsMagic, &tp.Stats) {
-				bolt.Pos = pos
-				used = true
-
-				if tp.Type == 'D' && name == "flame" {
-					g.addmsgf("the flame bounces")
-
-					if !g.Options.Terse {
-						g.addmsgf(" off the dragon")
-					}
-
-					g.endmsg()
-				} else {
-					g.hitMonster(pos, bolt)
-				}
-			} else if ch != 'M' || tp.Disguise == 'M' {
-				if fromHero {
-					g.runTo(pos)
-				}
-
-				if g.Options.Terse {
-					g.msg("%s misses", name)
-				} else {
-					g.msg("the %s whizzes past %s", name, g.setMname(tp))
-				}
-			}
 		} else if hitHero && pos == p.Pos {
 			hitHero = false
 			changed = !changed
-
+			used = g.boltStrikesHero(start, name, fromHero)
-			if !g.save(VsMagic) {
-				if p.Stats.HP -= g.roll(6, 6); p.Stats.HP <= 0 {
-					if fromHero {
-						g.death('b')
-					} else {
-						g.death(g.Level.MonsterAt(start.Y, start.X).Type)
-					}
-				}
-
-				used = true
-
-				if g.Options.Terse {
-					g.msg("the %s hits", name)
-				} else {
-					g.msg("you are hit by the %s", name)
-				}
-			} else {
-				g.msg("the %s whizzes by you", name)
-			}
 		}
 
 		g.mvaddch(pos.Y, pos.X, dirch)
@@ -446,6 +373,104 @@ func (g *RogueGame) fireBolt(start Coord, dir *Coord, name string) {
 	}
 }
 
+// boltDirChar picks the character a traveling bolt is drawn with for its
+// direction (the dirch switch of sticks.c fire_bolt).
+func boltDirChar(dir Coord) byte {
+	switch dir.Y + dir.X {
+	case 0:
+		return '/'
+	case 1, -1:
+		if dir.Y == 0 {
+			return '-'
+		}
+
+		return '|'
+	case 2, -2:
+		return '\\'
+	}
+
+	return 0 // unreachable for the eight legal directions, as in C
+}
+
+// boltBounces reports whether a bolt bounces off this spot: walls, and
+// any door except the one the hero stands on (which would otherwise loop
+// infinitely, per the C comment in fire_bolt).
+func boltBounces(ch byte, heroPos, pos Coord) bool {
+	switch ch {
+	case Door:
+		return heroPos != pos
+	case '|', '-', ' ':
+		return true
+	}
+
+	return false
+}
+
+// boltStrikesMonster resolves a bolt arriving on a monster's square (the
+// monster arm of the fire_bolt loop). It reports whether the bolt was
+// used up.
+func (g *RogueGame) boltStrikesMonster(tp *Monster, bolt *Object, pos Coord, ch byte, name string, fromHero bool) bool {
+	tp.OldCh = g.Level.Char(pos.Y, pos.X)
+	if !g.saveThrow(VsMagic, &tp.Stats) {
+		bolt.Pos = pos
+
+		if tp.Type == 'D' && name == "flame" {
+			g.addmsgf("the flame bounces")
+
+			if !g.Options.Terse {
+				g.addmsgf(" off the dragon")
+			}
+
+			g.endmsg()
+		} else {
+			g.hitMonster(pos, bolt)
+		}
+
+		return true
+	}
+
+	if ch != 'M' || tp.Disguise == 'M' {
+		if fromHero {
+			g.runTo(pos)
+		}
+
+		if g.Options.Terse {
+			g.msg("%s misses", name)
+		} else {
+			g.msg("the %s whizzes past %s", name, g.setMname(tp))
+		}
+	}
+
+	return false
+}
+
+// boltStrikesHero resolves a bolt arriving on the hero (the hero arm of
+// the fire_bolt loop). It reports whether the bolt was used up.
+func (g *RogueGame) boltStrikesHero(start Coord, name string, fromHero bool) bool {
+	p := &g.Player
+	if g.save(VsMagic) {
+		g.msg("the %s whizzes by you", name)
+
+		return false
+	}
+
+	if p.Stats.HP -= g.roll(6, 6); p.Stats.HP <= 0 {
+		if fromHero {
+			g.death('b')
+		} else {
+			g.death(g.Level.MonsterAt(start.Y, start.X).Type)
+		}
+	}
+
+	if g.Options.Terse {
+		g.msg("the %s hits", name)
+	} else {
+		g.msg("you are hit by the %s", name)
+	}
+
+	return true
+}
+
 // fixStick sets up a new wand or staff (sticks.c fix_stick).
 func (g *RogueGame) fixStick(cur *Object) {
 	if g.Items.WandType[cur.Which] == staffName {