rgoue/game/bolt_test.go

//nolint:testpackage // white-box tests reach unexported state (approved 2026-07-07)
package game

import (
	"slices"
	"testing"
)

// The bolt geometry of sticks.c fire_bolt, tested on the hand-carved
// level built by mkCarvedGame in sticks_test.go.
//
// Most of these fire from a square that is not the hero's, which is what
// chase.c does when a dragon breathes (fire_bolt(&th->t_pos, ...)). That
// keeps the hero off the ray, so the run produces exactly one message
// and the screen stays readable as a record of where the bolt went — see
// litCells.

// The three names sticks.c fires a bolt under (do_zap's WS_ELECT,
// WS_FIRE and WS_COLD arms); fire_bolt prints them and hangs them on the
// FLAME weapon-table entry.
const (
	boltName  = "bolt"
	flameName = "flame"
	iceName   = "ice"
)

// litCells reports every non-blank cell of the map area of the screen.
//
// fire_bolt paints its trail with dirch and then erases it by writing
// back chat() for each square it recorded, so on a screen nothing else
// has drawn on, the squares left non-blank are exactly the ones the bolt
// occupied. Squares it bounced off are absent by construction: C undoes
// the record with c1-- and breaks before the mvaddch, so a wall is
// neither painted nor erased.
func litCells(g *RogueGame) []Coord {
	var out []Coord
	// Row 0 is the message line, not the map.
	for y := 1; y < NumLines; y++ {
		line := g.scr.Std.Line(y)
		for x := range len(line) {
			if line[x] != ' ' {
				out = append(out, Coord{X: x, Y: y})
			}
		}
	}

	return out
}

// assertErased checks that every square the bolt flew over is showing
// the map character underneath it again: fire_bolt's closing loop paints
// chat() back over the whole trail, so a bolt leaves no '/' or '\'
// behind.
func assertErased(t *testing.T, g *RogueGame, cells []Coord) {
	t.Helper()

	for _, c := range cells {
		got := g.scr.Std.Line(c.Y)[c.X]
		if want := g.Level.Char(c.Y, c.X); got != want {
			t.Errorf("square %v shows %q, want the map's %q: the trail "+
				"was not erased", c, got, want)
		}
	}
}

// TestBoltDirChar covers the dirch switch for all eight directions. C
// keys it on dir->y + dir->x: the two sums of zero are the '/' pair, the
// two of magnitude two are the '\' pair, and the four axis directions
// split on whether y is zero.
func TestBoltDirChar(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name string
		dir  Coord
		want byte
	}{
		{name: "north", dir: Coord{X: 0, Y: -1}, want: '|'},
		{name: "south", dir: Coord{X: 0, Y: 1}, want: '|'},
		{name: "east", dir: Coord{X: 1, Y: 0}, want: '-'},
		{name: "west", dir: Coord{X: -1, Y: 0}, want: '-'},
		{name: "north east", dir: Coord{X: 1, Y: -1}, want: '/'},
		{name: "south west", dir: Coord{X: -1, Y: 1}, want: '/'},
		{name: "north west", dir: Coord{X: -1, Y: -1}, want: '\\'},
		{name: "south east", dir: Coord{X: 1, Y: 1}, want: '\\'},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			if got := boltDirChar(tt.dir); got != tt.want {
				t.Errorf("boltDirChar(%v) = %q, want %q", tt.dir, got, tt.want)
			}
		})
	}
}

// TestBoltBounces covers the case labels a bolt reflects off, and the
// door exception: C jumps to the default arm when the hero is standing
// on the door, "otherwise it would loop infinitely".
func TestBoltBounces(t *testing.T) {
	t.Parallel()

	const heroX, heroY = 5, 5

	tests := []struct {
		name string
		ch   byte
		pos  Coord
		want bool
	}{
		{name: "vertical wall", ch: '|', pos: Coord{X: 6, Y: 5}, want: true},
		{name: "horizontal wall", ch: '-', pos: Coord{X: 6, Y: 5}, want: true},
		{name: "solid rock", ch: ' ', pos: Coord{X: 6, Y: 5}, want: true},
		{name: "door", ch: Door, pos: Coord{X: 6, Y: 5}, want: true},
		{
			name: "the door under the hero",
			ch:   Door,
			pos:  Coord{X: heroX, Y: heroY},
			want: false,
		},
		{name: "floor", ch: Floor, pos: Coord{X: 6, Y: 5}, want: false},
		{name: "passage", ch: Passage, pos: Coord{X: 6, Y: 5}, want: false},
		{name: "staircase", ch: Stairs, pos: Coord{X: 6, Y: 5}, want: false},
		{name: "a monster", ch: 'Z', pos: Coord{X: 6, Y: 5}, want: false},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			hero := Coord{X: heroX, Y: heroY}
			if got := boltBounces(tt.ch, hero, tt.pos); got != tt.want {
				t.Errorf("boltBounces(%q) = %v, want %v", tt.ch, got, tt.want)
			}
		})
	}
}

// TestFireBoltFliesStraight is the end-to-end run with nothing in the
// way: six squares, BOLT_LENGTH of them, and the last one is where the
// bolt stops.
func TestFireBoltFliesStraight(t *testing.T) {
	t.Parallel()

	g := mkCarvedGame(t, 41)
	dir := Coord{X: 1, Y: 0}

	g.fireBolt(Coord{X: 2, Y: 2}, &dir, flameName)

	want := []Coord{
		{X: 3, Y: 2}, {X: 4, Y: 2}, {X: 5, Y: 2},
		{X: 6, Y: 2}, {X: 7, Y: 2}, {X: 8, Y: 2},
	}

	got := litCells(g)
	if !slices.Equal(got, want) {
		t.Errorf("bolt path = %v, want %v", got, want)
	}

	assertErased(t, g, got)

	if g.Msgs.Huh != "" {
		t.Errorf("a bolt that hit nothing said %q", g.Msgs.Huh)
	}

	if (dir != Coord{X: 1, Y: 0}) {
		t.Errorf("direction = %v, want it unchanged", dir)
	}
}

// TestFireBoltBounces covers the reflection rule in both wall
// orientations, off a corner, and — the case that separates C's rule
// from a plausible wrong one — diagonally off a vertical wall. C negates
// *both* components, so a bolt that came in at 45 degrees goes back the
// way it came instead of reflecting off the surface.
// boltBounceCase is one wall-bounce run: where the bolt sets off, which
// way it goes, the wall it must reflect off, and the squares it must end
// up having occupied.
type boltBounceCase struct {
	name  string
	start Coord
	dir   Coord
	wall  Coord
	want  []Coord
}

// run fires the case's bolt and checks its whole flight.
func (tt boltBounceCase) run(t *testing.T) {
	t.Helper()

	g := mkCarvedGame(t, 42)
	dir := tt.dir

	g.fireBolt(tt.start, &dir, flameName)

	got := litCells(g)
	if !slices.Equal(got, tt.want) {
		t.Errorf("bolt path = %v, want %v", got, tt.want)
	}

	assertErased(t, g, got)

	if slices.Contains(got, tt.wall) {
		t.Errorf("the wall at %v was drawn on; C drops the bounce "+
			"square from spotpos before the mvaddch", tt.wall)
	}

	if want := (Coord{X: -tt.dir.X, Y: -tt.dir.Y}); dir != want {
		t.Errorf("direction = %v after one bounce, want %v", dir, want)
	}

	if g.Msgs.Huh != "the flame bounces" {
		t.Errorf("message = %q, want %q", g.Msgs.Huh, "the flame bounces")
	}
}

func TestFireBoltBounces(t *testing.T) {
	t.Parallel()

	tests := []boltBounceCase{
		{
			name:  "off a vertical wall",
			start: Coord{X: 3, Y: corridorY},
			dir:   Coord{X: -1, Y: 0},
			wall:  Coord{X: 1, Y: corridorY},
			// Five squares, not six: the square in front of the wall is
			// flown over twice, and C charges spotpos for both.
			want: []Coord{
				{X: 2, Y: 4}, {X: 3, Y: 4}, {X: 4, Y: 4},
				{X: 5, Y: 4}, {X: 6, Y: 4},
			},
		},
		{
			name:  "off a horizontal wall",
			start: Coord{X: 5, Y: 2},
			dir:   Coord{X: 0, Y: -1},
			wall:  Coord{X: 5, Y: 1},
			want: []Coord{
				{X: 5, Y: 2}, {X: 5, Y: 3}, {X: 5, Y: 4},
				{X: 5, Y: 5}, {X: 5, Y: 6}, {X: 5, Y: 7},
			},
		},
		{
			name:  "off a corner",
			start: Coord{X: 3, Y: 3},
			dir:   Coord{X: -1, Y: -1},
			wall:  Coord{X: 1, Y: 1},
			want: []Coord{
				{X: 2, Y: 2}, {X: 3, Y: 3}, {X: 4, Y: 4},
				{X: 5, Y: 5}, {X: 6, Y: 6},
			},
		},
		{
			name:  "diagonally off a vertical wall",
			start: Coord{X: 3, Y: corridorY},
			dir:   Coord{X: -1, Y: -1},
			wall:  Coord{X: 1, Y: 2},
			want: []Coord{
				{X: 2, Y: 3}, {X: 3, Y: 4}, {X: 4, Y: 5},
				{X: 5, Y: 6}, {X: 6, Y: 7},
			},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()
			tt.run(t)
		})
	}
}

// TestFireBoltReboundsIntoHero covers the hit_hero/changed pair: a bolt
// the hero fires starts unable to hit him, and the first bounce flips
// that, so a wall one square away throws his own bolt back at him.
func TestFireBoltReboundsIntoHero(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		lvl      int
		wantMsg  string
		wantHurt bool
	}{
		{
			name:     "the hero saves",
			lvl:      saveProofLvl,
			wantMsg:  "the flame whizzes by you",
			wantHurt: false,
		},
		{
			name:     "the hero is hit",
			lvl:      1,
			wantMsg:  "you are hit by the flame",
			wantHurt: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			g := mkCarvedGame(t, 43)
			placeHero(g, Coord{X: roomAX + 1, Y: corridorY})
			fortify(g) // a bolt to the face must not exit the test binary
			g.Player.Stats.Lvl = tt.lvl

			pinRng(t, g, d20, 1) // the lowest save throw there is

			hp := g.Player.Stats.HP
			dir := Coord{X: -1, Y: 0}

			g.fireBolt(g.Player.Pos, &dir, flameName)

			if g.Msgs.Huh != tt.wantMsg {
				t.Errorf("message = %q, want %q", g.Msgs.Huh, tt.wantMsg)
			}

			lost := hp - g.Player.Stats.HP
			if hurt := lost > 0; hurt != tt.wantHurt {
				t.Errorf("hero lost %d hit points, want hurt = %v",
					lost, tt.wantHurt)
			}
			// roll(6, 6) is six to thirty-six.
			if tt.wantHurt && (lost < 6 || lost > 36) {
				t.Errorf("hero lost %d hit points, want 6..36", lost)
			}
		})
	}
}

// TestFireBoltFromDoorUnderHeroTerminates covers the guard C wrote the
// door case for: the hero standing on a door and firing into the wall
// that door sits in. Without the ce(hero, pos) exception the bolt
// bounces on his own square forever, never recording a spot and never
// filling spotpos, and fire_bolt does not return — this test hangs
// rather than fails if the exception is lost.
func TestFireBoltFromDoorUnderHeroTerminates(t *testing.T) {
	t.Parallel()

	g := mkCarvedGame(t, 44)
	placeHero(g, Coord{X: doorAX, Y: corridorY})
	fortify(g)

	pinRng(t, g, d20, 1) // no save: the strike ends the flight

	hp := g.Player.Stats.HP
	dir := Coord{X: 0, Y: -1} // north, into the wall the door is in

	g.fireBolt(g.Player.Pos, &dir, boltName)

	if g.Msgs.Huh != "you are hit by the bolt" {
		t.Errorf("message = %q, want the hero to be hit", g.Msgs.Huh)
	}

	if lost := hp - g.Player.Stats.HP; lost < 6 || lost > 36 {
		t.Errorf("hero lost %d hit points, want 6..36", lost)
	}
}

// TestFireBoltStrikesMonster covers the monster arm both ways, and the
// dragon's immunity to flame that C spells out in the same breath.
func TestFireBoltStrikesMonster(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name     string
		typ      byte
		lvl      int
		bolt     string
		wantMsg  string
		wantHurt bool
	}{
		{
			name:     "it fails its save",
			typ:      'Z',
			lvl:      1,
			bolt:     boltName,
			wantMsg:  "the bolt hits the zombie",
			wantHurt: true,
		},
		{
			name:     "it saves",
			typ:      'Z',
			lvl:      saveProofLvl,
			bolt:     boltName,
			wantMsg:  "the bolt whizzes past the zombie",
			wantHurt: false,
		},
		{
			name:     "a dragon shrugs off a flame",
			typ:      'D',
			lvl:      1,
			bolt:     flameName,
			wantMsg:  "the flame bounces off the dragon",
			wantHurt: false,
		},
		{
			name:     "but not a lightning bolt",
			typ:      'D',
			lvl:      1,
			bolt:     boltName,
			wantMsg:  "the bolt hits the dragon",
			wantHurt: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			g := mkCarvedGame(t, 45)
			placeHero(g, Coord{X: 5, Y: corridorY})

			tp := putMonster(g, tt.typ, Coord{X: 8, Y: corridorY})
			tp.Stats.Lvl = tt.lvl
			tp.Stats.HP = 500 // enough to survive 6x6 and stay assertable

			pinRng(t, g, d20, 1) // the lowest save throw there is

			dir := Coord{X: 1, Y: 0}
			g.fireBolt(g.Player.Pos, &dir, tt.bolt)

			if g.Msgs.Huh != tt.wantMsg {
				t.Errorf("message = %q, want %q", g.Msgs.Huh, tt.wantMsg)
			}

			if hurt := tp.Stats.HP < 500; hurt != tt.wantHurt {
				t.Errorf("monster hit points = %d, want hurt = %v",
					tp.Stats.HP, tt.wantHurt)
			}
		})
	}
}

// TestFireBoltMissedMonsterWakesUp covers the rest of the miss arm: a
// bolt the hero fired sets the monster running (runto) before it says
// what it whizzed past, and the bolt flies on for its full length.
func TestFireBoltMissedMonsterWakesUp(t *testing.T) {
	t.Parallel()

	g := mkCarvedGame(t, 46)
	placeHero(g, Coord{X: 5, Y: corridorY})

	tp := putMonster(g, 'Z', Coord{X: 8, Y: corridorY})
	tp.Stats.Lvl = saveProofLvl
	tp.Flags.Clear(Awake)

	dir := Coord{X: 1, Y: 0}
	g.fireBolt(g.Player.Pos, &dir, boltName)

	if !tp.On(Awake) {
		t.Error("the monster the bolt missed is still asleep")
	}

	if tp.Dest != &g.Player.Pos {
		t.Error("the woken monster is not chasing the hero")
	}

	if tp.OldCh != Floor {
		t.Errorf("under-character = %q, want %q: fire_bolt records chat() "+
			"before it resolves the save", tp.OldCh, Floor)
	}
}

// TestFireBoltMissSpeaksEvenForAnM pins the "ch != 'M' ||
// tp->t_disguise == 'M'" guard on C's miss message, which reads as
// though something looking like an 'M' can be missed silently. It
// cannot: ch comes from winat, and winat *is* t_disguise whenever a
// monster stands there (rogue.h 57), so ch == 'M' implies
// t_disguise == 'M' and the condition is always true. The guard is
// vestigial — 'M' was the mimic in earlier Rogues — and a port that
// "tidied" it into a real silence would go quiet where C speaks.
func TestFireBoltMissSpeaksEvenForAnM(t *testing.T) {
	t.Parallel()

	g := mkCarvedGame(t, 47)
	placeHero(g, Coord{X: 5, Y: corridorY})

	tp := putMonster(g, 'M', Coord{X: 8, Y: corridorY})
	tp.Stats.Lvl = saveProofLvl
	tp.Flags.Clear(Awake)

	dir := Coord{X: 1, Y: 0}
	g.fireBolt(g.Player.Pos, &dir, boltName)

	const want = "the bolt whizzes past the medusa"
	if g.Msgs.Huh != want {
		t.Errorf("message = %q, want %q", g.Msgs.Huh, want)
	}

	if !tp.On(Awake) {
		t.Error("the missed medusa was not set running")
	}
}