Convert doZap to a per-wand handler table (refactor step 7)

The do_zap switch becomes gameData.zapHandlers, indexed by WandKind;
the shared monster-ray preamble is zapRayMonster/zapVictim, teleport
away/to and the three bolt wands share handlers, and a false return
aborts the zap without spending a charge (drain life on a too-weak
hero, as in C). Effect order and RNG call sequence unchanged.

game/sticks.go

@@ -12,8 +12,6 @@ const (
 
 // doZap performs a zap with a wand (sticks.c do_zap).
 func (g *RogueGame) doZap() {
-	p := &g.Player
-
 	obj, ok := g.promptPackItem("zap with", KindWand)
 	if !ok {
 		return
@@ -32,9 +30,51 @@ func (g *RogueGame) doZap() {
 		return
 	}
 
-	switch obj.WandKind() {
+	if h := g.data.zapHandlers[obj.WandKind()]; h != nil {
-	case WandLight:
+		if !h(g, obj) {
+			return // the zap aborted; no charge is used
+		}
+	}
+
+	obj.Charges--
+}
+
+// zapRayMonster walks the zap ray from the hero to the first blocking
+// spot and returns the monster standing there, if any (the shared
+// preamble of the C monster-affecting zap cases).
+func (g *RogueGame) zapRayMonster() *Monster {
+	p := &g.Player
+
+	y := p.Pos.Y
+
+	x := p.Pos.X
+	for stepOk(g.Level.VisibleChar(y, x)) {
+		y += g.Delta.Y
+		x += g.Delta.X
+	}
+
+	return g.Level.MonsterAt(y, x)
+}
+
+// zapVictim is zapRayMonster plus the flytrap release the C code does
+// before the invisibility-family effects.
+func (g *RogueGame) zapVictim() *Monster {
+	tp := g.zapRayMonster()
+	if tp != nil && tp.Type == 'F' {
+		g.Player.Flags.Clear(Held)
+	}
+
+	return tp
+}
+
+// The per-wand effect handlers, dispatched through gameData.zapHandlers.
+// Each is one case of the C do_zap switch; returning false aborts the
+// zap without using a charge.
+
+func (g *RogueGame) zapLight(*Object) bool {
 	// Reddy Kilowatt wand.  Light up the room
+	p := &g.Player
+
 	g.Items.Sticks[WandLight].Know = true
 	if p.Room.Flags.Has(Gone) {
 		g.msg("the corridor glows and then fades")
@@ -50,40 +90,45 @@ func (g *RogueGame) doZap() {
 
 		g.endmsg()
 	}
-	case WandDrainLife:
+
+	return true
+}
+
+func (g *RogueGame) zapDrainLife(*Object) bool {
 	// take away 1/2 of hero's hit points, then take it away evenly
 	// from the monsters in the room (or next to hero if he is in a
 	// passage)
-		if p.Stats.HP < 2 {
+	if g.Player.Stats.HP < 2 {
 		g.msg("you are too weak to use it")
 
-			return
+		return false
 	}
 
 	g.drain()
-	case WandInvisibility, WandPolymorph, WandTeleportAway, WandTeleportTo, WandCancellation:
-		y := p.Pos.Y
 
-		x := p.Pos.X
+	return true
-		for stepOk(g.Level.VisibleChar(y, x)) {
+}
-			y += g.Delta.Y
-			x += g.Delta.X
-		}
 
-		if tp := g.Level.MonsterAt(y, x); tp != nil {
+func (g *RogueGame) zapInvisibility(*Object) bool {
-			monster := tp.Type
+	if tp := g.zapVictim(); tp != nil {
-			if monster == 'F' {
-				p.Flags.Clear(Held)
-			}
-
-			switch obj.WandKind() {
-			case WandInvisibility:
 		tp.Flags.Set(Invisible)
 
-				if g.canSee(y, x) {
+		if g.canSee(tp.Pos.Y, tp.Pos.X) {
-					g.mvaddch(y, x, tp.OldCh)
+			g.mvaddch(tp.Pos.Y, tp.Pos.X, tp.OldCh)
 		}
-			case WandPolymorph:
+	}
+
+	return true
+}
+
+func (g *RogueGame) zapPolymorph(*Object) bool {
+	tp := g.zapVictim()
+	if tp == nil {
+		return true
+	}
+
+	y, x := tp.Pos.Y, tp.Pos.X
+
 	pp := tp.Pack
 	g.Level.RemoveMonster(tp)
 
@@ -94,7 +139,7 @@ func (g *RogueGame) doZap() {
 	oldch := tp.OldCh
 	g.Delta.Y = y
 	g.Delta.X = x
-				monster = g.randomMonsterLetter()
+	monster := g.randomMonsterLetter()
 	g.newMonster(tp, monster, g.Delta)
 
 	if g.seeMonst(tp) {
@@ -107,15 +152,32 @@ func (g *RogueGame) doZap() {
 	if g.seeMonst(tp) {
 		g.Items.Sticks[WandPolymorph].Know = true
 	}
-			case WandCancellation:
+
+	return true
+}
+
+func (g *RogueGame) zapCancellation(*Object) bool {
+	if tp := g.zapVictim(); tp != nil {
 		tp.Flags.Set(Cancelled)
 		tp.Flags.Clear(Invisible | CanConfuse)
 
 		tp.Disguise = tp.Type
 		if g.seeMonst(tp) {
-					g.mvaddch(y, x, tp.Disguise)
+			g.mvaddch(tp.Pos.Y, tp.Pos.X, tp.Disguise)
 		}
-			case WandTeleportAway, WandTeleportTo:
+	}
+
+	return true
+}
+
+func (g *RogueGame) zapTeleport(obj *Object) bool {
+	p := &g.Player
+
+	tp := g.zapVictim()
+	if tp == nil {
+		return true
+	}
+
 	var newPos Coord
 
 	if obj.WandKind() == WandTeleportAway {
@@ -133,9 +195,13 @@ func (g *RogueGame) doZap() {
 	tp.Dest = &p.Pos
 	tp.Flags.Set(Awake)
 	g.relocate(tp, newPos)
-			}
+
-		}
+	return true
-	case WandMagicMissile:
+}
+
+func (g *RogueGame) zapMagicMissile(*Object) bool {
+	p := &g.Player
+
 	g.Items.Sticks[WandMagicMissile].Know = true
 	bolt := newObject()
 	bolt.Kind = KindGold // C set o_type='*': draws a '*' and is not a weapon
@@ -158,16 +224,12 @@ func (g *RogueGame) doZap() {
 	} else {
 		g.msg("the missle vanishes with a puff of smoke") //nolint:misspell // C's spelling
 	}
-	case WandHasteMonster, WandSlowMonster:
-		y := p.Pos.Y
 
-		x := p.Pos.X
+	return true
-		for stepOk(g.Level.VisibleChar(y, x)) {
+}
-			y += g.Delta.Y
-			x += g.Delta.X
-		}
 
-		if tp := g.Level.MonsterAt(y, x); tp != nil {
+func (g *RogueGame) zapSpeed(obj *Object) bool {
+	if tp := g.zapRayMonster(); tp != nil {
 		if obj.WandKind() == WandHasteMonster {
 			if tp.On(Slowed) {
 				tp.Flags.Clear(Slowed)
@@ -184,11 +246,15 @@ func (g *RogueGame) doZap() {
 			tp.Turn = true
 		}
 
-			g.Delta.Y = y
+		g.Delta.Y = tp.Pos.Y
-			g.Delta.X = x
+		g.Delta.X = tp.Pos.X
 		g.runTo(g.Delta)
 	}
-	case WandLightning, WandFire, WandCold:
+
+	return true
+}
+
+func (g *RogueGame) zapBolt(obj *Object) bool {
 	var name string
 
 	switch obj.WandKind() {
@@ -200,12 +266,10 @@ func (g *RogueGame) doZap() {
 		name = "ice"
 	}
 
-		g.fireBolt(p.Pos, &g.Delta, name)
+	g.fireBolt(g.Player.Pos, &g.Delta, name)
 	g.Items.Sticks[obj.Which].Know = true
-	case WandNothing:
-	}
 
-	obj.Charges--
+	return true
 }
 
 // drain does the drain-hit-points-from-player schtick (sticks.c drain).

game/tables.go

@@ -132,6 +132,11 @@ type gameData struct {
 	// the cases of the scrolls.c read_scroll switch. The handler gets
 	// the scroll being read (the identify family needs its subtype).
 	readHandlers [NumScrollTypes]func(g *RogueGame, obj *Object)
+
+	// zapHandlers dispatches each wand kind to its effect method: the
+	// cases of the sticks.c do_zap switch. A false return aborts the
+	// zap without using a charge (drain life on a too-weak hero).
+	zapHandlers [NumWandTypes]func(g *RogueGame, obj *Object) bool
 }
 
 // ripWall is the repeated blank wall line of the tombstone art.
@@ -635,6 +640,22 @@ func newGameData() *gameData {
 			ScrollAggravateMonsters:   (*RogueGame).readAggravateMonsters,
 			ScrollProtectArmor:        (*RogueGame).readProtectArmor,
 		},
+
+		zapHandlers: [NumWandTypes]func(*RogueGame, *Object) bool{
+			WandLight:        (*RogueGame).zapLight,
+			WandInvisibility: (*RogueGame).zapInvisibility,
+			WandLightning:    (*RogueGame).zapBolt,
+			WandFire:         (*RogueGame).zapBolt,
+			WandCold:         (*RogueGame).zapBolt,
+			WandPolymorph:    (*RogueGame).zapPolymorph,
+			WandMagicMissile: (*RogueGame).zapMagicMissile,
+			WandHasteMonster: (*RogueGame).zapSpeed,
+			WandSlowMonster:  (*RogueGame).zapSpeed,
+			WandDrainLife:    (*RogueGame).zapDrainLife,
+			WandTeleportAway: (*RogueGame).zapTeleport,
+			WandTeleportTo:   (*RogueGame).zapTeleport,
+			WandCancellation: (*RogueGame).zapCancellation,
+		},
 	}
 }