[Space Lua]: Implement math.random and math.randomseed (#1845)

client/space_lua/stdlib/math_test.lua

@@ -25,6 +25,13 @@ local function assertClose(a, b, eps, msg)
   end
 end
 
+local function assertError(fn, msg)
+  local ok, err = pcall(fn)
+  if ok then
+    error((msg or "assertError failed") .. ": expected an error but none was raised")
+  end
+end
+
 -- math.type (basic)
 do
   assertEquals(math.type(0), "integer", "math.type(0)")
@@ -161,3 +168,111 @@ do
   assertEquals(f2, 3, "floor(8*0.49)")
   assertEquals(f3, 4, "floor(9*0.5)")
 end
+
+-- random and randomseed
+do
+  -- random(): float in [0, 1)
+  for _ = 1, 20 do
+    local v = math.random()
+    assertTrue(v >= 0 and v < 1, "random() in [0,1)")
+    assertEquals(math.type(v), "float", "random() returns float")
+  end
+
+  -- random(n): integer in [1, n]
+  for _ = 1, 20 do
+    local v = math.random(10)
+    assertTrue(v >= 1 and v <= 10, "random(10) in [1,10]")
+    assertEquals(math.type(v), "integer", "random(n) returns integer")
+  end
+
+  -- random(m, n): integer in [m, n]
+  for _ = 1, 20 do
+    local v = math.random(5, 10)
+    assertTrue(v >= 5 and v <= 10, "random(5,10) in [5,10]")
+    assertEquals(math.type(v), "integer", "random(m,n) returns integer")
+  end
+
+  -- random(m, m): always returns m
+  for _ = 1, 5 do
+    assertEquals(math.random(7, 7), 7, "random(m,m) == m")
+  end
+
+  -- random(0): raw 64-bit integer, type integer
+  local r0 = math.random(0)
+  assertEquals(math.type(r0), "integer", "random(0) returns integer")
+
+  -- random(n) with n=1: always 1
+  for _ = 1, 5 do
+    assertEquals(math.random(1), 1, "random(1) == 1")
+  end
+
+  -- error: random(0.5) — non-integer arg1
+  assertError(function() math.random(0.5) end)
+
+  -- error: random(1, 0) — empty interval
+  assertError(function() math.random(1, 0) end)
+
+  -- error: random(0) is valid (raw), but random(-1) is not
+  assertError(function() math.random(-1) end)
+
+  -- error: random(1, 1.5) — non-integer arg2
+  assertError(function() math.random(1, 1.5) end)
+
+  -- randomseed arg validation
+  assertError(function() math.randomseed(0.5) end)
+  assertError(function() math.randomseed(1, 0.5) end)
+  assertError(function() math.randomseed(1/0) end)
+end
+
+-- randomseed: determinism
+do
+  -- same seed yields identical sequence
+  math.randomseed(42)
+  local a1, a2, a3 = math.random(), math.random(100), math.random(1, 50)
+
+  math.randomseed(42)
+  local b1, b2, b3 = math.random(), math.random(100), math.random(1, 50)
+
+  assertEquals(a1, b1, "randomseed: float sequence reproducible")
+  assertEquals(a2, b2, "randomseed: random(n) reproducible")
+  assertEquals(a3, b3, "randomseed: random(m,n) reproducible")
+
+  -- different seeds yields different first values
+  math.randomseed(1)
+  local c1 = math.random()
+  math.randomseed(2)
+  local d1 = math.random()
+  assertTrue(c1 ~= d1, "different seeds give different values")
+
+  -- two-argument seed: same pair yields same sequence
+  math.randomseed(123, 456)
+  local e1, e2 = math.random(), math.random()
+  math.randomseed(123, 456)
+  local f1, f2 = math.random(), math.random()
+  assertEquals(e1, f1, "randomseed(x,y): first value reproducible")
+  assertEquals(e2, f2, "randomseed(x,y): second value reproducible")
+
+  -- two-argument seed: different second arg yields different sequence
+  math.randomseed(123, 456)
+  local g1 = math.random()
+  math.randomseed(123, 789)
+  local h1 = math.random()
+  assertTrue(g1 ~= h1, "randomseed(x,y1) ~= randomseed(x,y2)")
+
+  -- no-args seed does not error and produces valid range
+  math.randomseed()
+  local i1 = math.random()
+  assertTrue(i1 >= 0 and i1 < 1, "randomseed(): range valid after auto-seed")
+
+  -- return values: two integers (Lua 5.4 contract)
+  local s1, s2 = math.randomseed(99)
+  assertEquals(math.type(s1), "integer", "randomseed returns integer s1")
+  assertEquals(math.type(s2), "integer", "randomseed returns integer s2")
+
+  -- re-seeding restores determinism after auto-seed
+  math.randomseed(7)
+  local j1 = math.random()
+  math.randomseed(7)
+  local j2 = math.random()
+  assertEquals(j1, j2, "determinism restored after re-seed")
+end