// Tests for the IR-to-LLVM emitter (emit_llvm.zig).

const std = @import("std");
const types = @import("types.zig");
const inst_mod = @import("inst.zig");
const mod_mod = @import("module.zig");
const emit_mod = @import("emit_llvm.zig");

const TypeId = types.TypeId;
const Ref = inst_mod.Ref;
const FuncId = inst_mod.FuncId;
const Function = inst_mod.Function;
const Module = mod_mod.Module;
const Builder = mod_mod.Builder;
const LLVMEmitter = emit_mod.LLVMEmitter;

// ── Helper ──────────────────────────────────────────────────────────────

fn str(module: *Module, s: []const u8) types.StringId {
    return module.types.internString(s);
}

// ── Tests ───────────────────────────────────────────────────────────────

test "emit: main() returns 42" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func main() -> s64 { return 42; }
    _ = b.beginFunction(str(&module, "main"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);
    const c42 = b.constInt(42, .s64);
    b.ret(c42, .s64);
    b.finalize();

    // Emit to LLVM
    var emitter = LLVMEmitter.init(alloc, &module, "test_ret42", .{});
    defer emitter.deinit();
    emitter.emit();

    // Verify the module is valid
    try std.testing.expect(emitter.verify());

    // Check LLVM IR contains expected patterns
    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "define") != null);
    // `main` is emitted with the C entry-point convention: it returns i32, so
    // the s64 const 42 is truncated to `ret i32 42`.
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i32 42") != null);
}

test "emit: add(a, b) returns a + b" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func add(a: s64, b: s64) -> s64 { return a + b; }
    const params = &[_]Function.Param{
        .{ .name = str(&module, "a"), .ty = .s64 },
        .{ .name = str(&module, "b"), .ty = .s64 },
    };
    _ = b.beginFunction(str(&module, "add"), params, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    // Parameters are refs 0 and 1 — but in our IR they're passed as
    // arguments to the interpreter. For the LLVM emitter, we need to
    // load them from LLVM function params. For now, use constInt as
    // placeholders since we haven't wired up param→ref mapping yet.
    //
    // Actually, looking at the IR design: the Builder's inst_counter starts
    // at 0, and params are accessed differently. The lowering pass emits
    // alloca+store for params. For this test, we use const_int to test
    // the add instruction directly.
    const a = b.constInt(10, .s64);
    const a_b = b.constInt(32, .s64);
    const sum = b.add(a, a_b, .s64);
    b.ret(sum, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_add", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "add") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: float arithmetic" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // Operands must be non-constant (function params) or LLVM constant-folds
    // the arithmetic away and no fadd/fmul instruction is emitted.
    _ = b.beginFunction(str(&module, "fmath"), &[_]Function.Param{
        .{ .name = str(&module, "x"), .ty = .f64 },
        .{ .name = str(&module, "y"), .ty = .f64 },
    }, .f64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const a = Ref.fromIndex(0);
    const a_b = Ref.fromIndex(1);
    const sum = b.add(a, a_b, .f64);
    const product = b.mul(sum, a_b, .f64);
    b.ret(product, .f64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_float", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "fadd") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "fmul") != null);
}

test "emit: negation" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // Negating a constant folds; negate a param so `sub 0, %x` is emitted.
    _ = b.beginFunction(str(&module, "negate"), &[_]Function.Param{
        .{ .name = str(&module, "x"), .ty = .s64 },
    }, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const val = Ref.fromIndex(0);
    const neg = b.emit(.{ .neg = .{ .operand = val } }, .s64);
    b.ret(neg, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_neg", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // LLVM represents neg as "sub nsw i64 0, %val" or "sub i64 0, %val"
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "sub") != null);
}

test "emit: void function" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    _ = b.beginFunction(str(&module, "noop"), &.{}, .void);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);
    b.retVoid();
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_void", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret void") != null);
}

test "emit: alloca, store, load" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func f() -> s64 { var x: s64 = 10; return x; }
    _ = b.beginFunction(str(&module, "f"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const x_ptr = b.alloca(.s64); // alloca s64 → *s64
    const ten = b.constInt(10, .s64);
    b.store(x_ptr, ten); // store 10 → *x
    const loaded = b.load(x_ptr, .s64); // load *x → s64
    b.ret(loaded, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_mem", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "alloca") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "store") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "load") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: comparison and branch" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func f(a, b) -> s64 { if (a < b) return 1; else return 0; }
    // Params (not constants) so the icmp isn't folded.
    _ = b.beginFunction(str(&module, "cmpfn"), &[_]Function.Param{
        .{ .name = str(&module, "a"), .ty = .s64 },
        .{ .name = str(&module, "b"), .ty = .s64 },
    }, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    const then_bb = b.appendBlock(str(&module, "then"), &.{});
    const else_bb = b.appendBlock(str(&module, "else"), &.{});
    b.switchToBlock(entry);

    const a = Ref.fromIndex(0);
    const b_val = Ref.fromIndex(1);
    const cond = b.cmpLt(a, b_val);
    b.condBr(cond, then_bb, &.{}, else_bb, &.{});

    b.switchToBlock(then_bb);
    const one = b.constInt(1, .s64);
    b.ret(one, .s64);

    b.switchToBlock(else_bb);
    const zero = b.constInt(0, .s64);
    b.ret(zero, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_cmp", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "icmp") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "br i1") != null);
}

test "emit: function call" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func add(a: s64, b: s64) -> s64 { return a + b; }  (using constants)
    const add_id = b.beginFunction(str(&module, "addfn"), &[_]Function.Param{
        .{ .name = str(&module, "a"), .ty = .s64 },
        .{ .name = str(&module, "b"), .ty = .s64 },
    }, .s64);
    const add_entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(add_entry);
    const p0 = b.constInt(0, .s64); // placeholder
    const p1 = b.constInt(0, .s64);
    const sum = b.add(p0, p1, .s64);
    b.ret(sum, .s64);
    b.finalize();

    // func main() -> s64 { return addfn(3, 4); }
    _ = b.beginFunction(str(&module, "main"), &.{}, .s64);
    const main_entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(main_entry);
    const three = b.constInt(3, .s64);
    const four = b.constInt(4, .s64);
    const result = b.call(add_id, &.{ three, four }, .s64);
    b.ret(result, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_call", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "call") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "addfn") != null);
}

test "emit: widen conversion s32 to s64" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // sext of a constant folds; widen a param so `sext` is emitted.
    _ = b.beginFunction(str(&module, "wfn"), &[_]Function.Param{
        .{ .name = str(&module, "x"), .ty = .s32 },
    }, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const val = Ref.fromIndex(0);
    const wide = b.widen(val, .s32, .s64);
    b.ret(wide, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_widen", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "sext") != null);
}

test "emit: type conversion toLLVMType" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var emitter = LLVMEmitter.init(alloc, &module, "test_types", .{});
    defer emitter.deinit();

    // Just verify toLLVMType doesn't crash for all builtin types
    _ = emitter.toLLVMType(.void);
    _ = emitter.toLLVMType(.bool);
    _ = emitter.toLLVMType(.s8);
    _ = emitter.toLLVMType(.s16);
    _ = emitter.toLLVMType(.s32);
    _ = emitter.toLLVMType(.s64);
    _ = emitter.toLLVMType(.u8);
    _ = emitter.toLLVMType(.u16);
    _ = emitter.toLLVMType(.u32);
    _ = emitter.toLLVMType(.u64);
    _ = emitter.toLLVMType(.f32);
    _ = emitter.toLLVMType(.f64);
    _ = emitter.toLLVMType(.string);
    _ = emitter.toLLVMType(.any);
    _ = emitter.toLLVMType(.noreturn);
}

// ── A7.1 scaffolding: ABI param coercion ────────────────────────────
// Lock the C-ABI struct-coercion buckets (abiCoerceParamType / needsByval),
// which feed callconv(.c) / #foreign signatures, before they move to
// src/backend/llvm/abi.zig in A7.1 sub-step 2.

const llvm = @import("../llvm_api.zig");
const cc = llvm.c;

fn internStruct(module: *Module, name: []const u8, field_tys: []const TypeId) TypeId {
    var fields = std.ArrayList(types.TypeInfo.StructInfo.Field).empty;
    defer fields.deinit(std.testing.allocator);
    for (field_tys, 0..) |fty, i| {
        var nb: [8]u8 = undefined;
        const fname = std.fmt.bufPrint(&nb, "f{d}", .{i}) catch unreachable;
        fields.append(std.testing.allocator, .{ .name = str(module, fname), .ty = fty }) catch unreachable;
    }
    // Dupe into the module arena so the interned struct's field slice lives for
    // the module's lifetime (freed at module.deinit) — no testing-allocator leak.
    const owned = module.slice_arena.allocator().dupe(types.TypeInfo.StructInfo.Field, fields.items) catch unreachable;
    return module.types.intern(.{ .@"struct" = .{ .name = str(module, name), .fields = owned } });
}

test "emit: abiCoerceParamType coerces C-ABI structs by size bucket" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    // Intern the shapes before building the emitter (toLLVMType reads live).
    const small = internStruct(&module, "Small", &.{ .s32, .s32 }); // 8 bytes
    const mid = internStruct(&module, "Mid", &.{ .s64, .s64 }); //    16 bytes
    const big = internStruct(&module, "Big", &.{ .s64, .s64, .s64 }); // 24 bytes
    const hfa_f = internStruct(&module, "HfaF", &.{ .f32, .f32, .f32, .f32 }); // 16, all-float
    const hfa_d = internStruct(&module, "HfaD", &.{ .f64, .f64 }); // 16, all-double
    const sl = module.types.sliceOf(.s32);

    var emitter = LLVMEmitter.init(alloc, &module, "test_abi", .{});
    defer emitter.deinit();

    // ≤ 8 bytes → i64.
    try std.testing.expect(emitter.abiCoerceParamType(small, emitter.toLLVMType(small)) == emitter.cached_i64);
    // 9–16 bytes → [2 x i64].
    try std.testing.expect(emitter.abiCoerceParamType(mid, emitter.toLLVMType(mid)) == cc.LLVMArrayType2(emitter.cached_i64, 2));
    // > 16 bytes → ptr (passed byval at the call/sig sites).
    try std.testing.expect(emitter.abiCoerceParamType(big, emitter.toLLVMType(big)) == emitter.cached_ptr);
    // HFA (all-float / all-double, ≤ 4 fields) → unchanged.
    try std.testing.expect(emitter.abiCoerceParamType(hfa_f, emitter.toLLVMType(hfa_f)) == emitter.toLLVMType(hfa_f));
    try std.testing.expect(emitter.abiCoerceParamType(hfa_d, emitter.toLLVMType(hfa_d)) == emitter.toLLVMType(hfa_d));
    // string / slice collapse to ptr at the C-API boundary (len dropped).
    try std.testing.expect(emitter.abiCoerceParamType(.string, emitter.toLLVMType(.string)) == emitter.cached_ptr);
    try std.testing.expect(emitter.abiCoerceParamType(sl, emitter.toLLVMType(sl)) == emitter.cached_ptr);
    // Scalars pass through unchanged.
    try std.testing.expect(emitter.abiCoerceParamType(.s32, emitter.toLLVMType(.s32)) == emitter.toLLVMType(.s32));
}

test "emit: needsByval only for > 16-byte non-HFA structs" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const small = internStruct(&module, "Small", &.{ .s32, .s32 });
    const mid = internStruct(&module, "Mid", &.{ .s64, .s64 });
    const big = internStruct(&module, "Big", &.{ .s64, .s64, .s64 });
    const hfa_d = internStruct(&module, "HfaD", &.{ .f64, .f64 });
    const sl = module.types.sliceOf(.s32);

    var emitter = LLVMEmitter.init(alloc, &module, "test_byval", .{});
    defer emitter.deinit();

    try std.testing.expect(emitter.needsByval(big, emitter.toLLVMType(big))); // > 16
    try std.testing.expect(!emitter.needsByval(small, emitter.toLLVMType(small)));
    try std.testing.expect(!emitter.needsByval(mid, emitter.toLLVMType(mid))); // exactly 16
    try std.testing.expect(!emitter.needsByval(hfa_d, emitter.toLLVMType(hfa_d))); // HFA
    try std.testing.expect(!emitter.needsByval(.string, emitter.toLLVMType(.string)));
    try std.testing.expect(!emitter.needsByval(sl, emitter.toLLVMType(sl)));
    try std.testing.expect(!emitter.needsByval(.s32, emitter.toLLVMType(.s32))); // non-struct
}

// ── Struct/Enum/Union tests ─────────────────────────────────────────

test "emit: struct_init and struct_get" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    // Create a struct type: Point { x: s64, y: s64 }
    const fields = &[_]types.TypeInfo.StructInfo.Field{
        .{ .name = str(&module, "x"), .ty = .s64 },
        .{ .name = str(&module, "y"), .ty = .s64 },
    };
    const owned_fields = alloc.dupe(types.TypeInfo.StructInfo.Field, fields) catch unreachable;
    defer alloc.free(owned_fields);
    const point_ty = module.types.intern(.{ .@"struct" = .{
        .name = str(&module, "Point"),
        .fields = owned_fields,
    } });

    var b = Builder.init(&module);

    // func f(v) -> s64 { p = Point{v, 20}; return p.y; }
    // A param operand keeps the aggregate non-constant so insertvalue /
    // extractvalue survive (a fully-constant struct would be folded).
    _ = b.beginFunction(str(&module, "f"), &[_]Function.Param{
        .{ .name = str(&module, "v"), .ty = .s64 },
    }, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const x = Ref.fromIndex(0);
    const y = b.constInt(20, .s64);
    const p = b.structInit(&.{ x, y }, point_ty);
    const py = b.structGet(p, 1, .s64);
    b.ret(py, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_struct", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "insertvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "extractvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: struct_gep (pointer to field)" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    // Create struct type
    const fields = &[_]types.TypeInfo.StructInfo.Field{
        .{ .name = str(&module, "x"), .ty = .s64 },
        .{ .name = str(&module, "y"), .ty = .s64 },
    };
    const owned_fields = alloc.dupe(types.TypeInfo.StructInfo.Field, fields) catch unreachable;
    defer alloc.free(owned_fields);
    const point_ty = module.types.intern(.{ .@"struct" = .{
        .name = str(&module, "Point"),
        .fields = owned_fields,
    } });
    const ptr_s64 = module.types.ptrTo(.s64);

    var b = Builder.init(&module);

    // func f() -> s64 { var p: Point; p.y = 42; return p.y; }
    _ = b.beginFunction(str(&module, "gepfn"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const p_ptr = b.alloca(point_ty);
    const y_ptr = b.structGepTyped(p_ptr, 1, ptr_s64, point_ty);
    const c42 = b.constInt(42, .s64);
    b.store(y_ptr, c42);
    const loaded = b.load(y_ptr, .s64);
    b.ret(loaded, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_gep", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "getelementptr") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "store") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: enum_init and enum_tag (plain enum)" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    // Create a plain enum type: Color { Red, Green, Blue }
    const variants = &[_]types.StringId{
        str(&module, "Red"),
        str(&module, "Green"),
        str(&module, "Blue"),
    };
    const owned_variants = alloc.dupe(types.StringId, variants) catch unreachable;
    defer alloc.free(owned_variants);
    const color_ty = module.types.intern(.{ .@"enum" = .{
        .name = str(&module, "Color"),
        .variants = owned_variants,
    } });

    var b = Builder.init(&module);

    // func f() -> s64 { c = Color.Green; return tag(c); }
    _ = b.beginFunction(str(&module, "enumfn"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const green = b.enumInit(1, Ref.none, color_ty); // Green = tag 1
    const tag = b.enumTag(green, .s32);
    // Widen tag from s32 to s64 for the return
    const wide = b.widen(tag, .s32, .s64);
    b.ret(wide, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_enum", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // Plain enum is just an integer constant
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: tagged union (enum_init with payload, enum_tag, enum_payload)" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    // Create a tagged union: Shape { Circle: f64, Rect: s64 }
    const ufields = &[_]types.TypeInfo.StructInfo.Field{
        .{ .name = str(&module, "Circle"), .ty = .f64 },
        .{ .name = str(&module, "Rect"), .ty = .s64 },
    };
    const owned_ufields = alloc.dupe(types.TypeInfo.StructInfo.Field, ufields) catch unreachable;
    defer alloc.free(owned_ufields);
    const shape_ty = module.types.intern(.{ .tagged_union = .{
        .name = str(&module, "Shape"),
        .fields = owned_ufields,
        .tag_type = .s64,
    } });

    var b = Builder.init(&module);

    // func f(r) -> f64 { s = Shape.Circle(r); ...; return payload; }
    // Param payload keeps the union value non-constant (else folded).
    _ = b.beginFunction(str(&module, "unionfn"), &[_]Function.Param{
        .{ .name = str(&module, "r"), .ty = .f64 },
    }, .f64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const radius = Ref.fromIndex(0);
    const shape = b.enumInit(0, radius, shape_ty); // Circle = tag 0
    const tag = b.emit(.{ .enum_tag = .{ .operand = shape } }, .s64);
    _ = tag; // tag is used but we just check it doesn't crash
    const payload = b.emit(.{ .enum_payload = .{ .base = shape, .field_index = 0 } }, .f64);
    b.ret(payload, .f64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_union", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // Tagged-union enum_init/enum_payload lower to a memory pattern
    // (alloca + GEP + store/load), not SSA insert/extractvalue. enum_tag
    // does emit extractvalue.
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "alloca") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "getelementptr") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "extractvalue") != null);
}

test "emit: union_get (reinterpret union field)" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    // Untagged union: Data { as_int: s64, as_float: f64 }
    const ufields = &[_]types.TypeInfo.StructInfo.Field{
        .{ .name = str(&module, "as_int"), .ty = .s64 },
        .{ .name = str(&module, "as_float"), .ty = .f64 },
    };
    const owned_ufields = alloc.dupe(types.TypeInfo.StructInfo.Field, ufields) catch unreachable;
    defer alloc.free(owned_ufields);
    const data_ty = module.types.intern(.{ .@"union" = .{
        .name = str(&module, "Data"),
        .fields = owned_ufields,
    } });

    var b = Builder.init(&module);

    // func f() -> s64 { d = Data.as_int(42); return union_get(d, 0) as s64; }
    _ = b.beginFunction(str(&module, "ugfn"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const val = b.constInt(42, .s64);
    const d = b.enumInit(0, val, data_ty);
    const got = b.emit(.{ .union_get = .{ .base = d, .field_index = 0 } }, .s64);
    b.ret(got, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_union_get", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // Should contain alloca + store + GEP + load pattern
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "alloca") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "load") != null);
}

// ── Array/Slice tests ───────────────────────────────────────────────

test "emit: array index_get" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const arr_ty = module.types.arrayOf(.s64, 3);

    var b = Builder.init(&module);

    // func f() -> s64 { arr: [3]s64 = ---; return arr[1]; }
    _ = b.beginFunction(str(&module, "arr_idx"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const undef_arr = b.emit(.{ .const_undef = {} }, arr_ty);
    const idx = b.constInt(1, .s64);
    const elem = b.emit(.{ .index_get = .{ .lhs = undef_arr, .rhs = idx } }, .s64);
    b.ret(elem, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_arr_idx", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "getelementptr") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: length on slice" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func f(s: string) -> s64 { return s.len; }
    // A string param keeps the value non-constant so extractvalue survives.
    _ = b.beginFunction(str(&module, "strlen"), &[_]Function.Param{
        .{ .name = str(&module, "s"), .ty = .string },
    }, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const s = Ref.fromIndex(0);
    const len = b.emit(.{ .length = .{ .operand = s } }, .s64);
    b.ret(len, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_len", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "extractvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: data_ptr on slice" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const ptr_ty = module.types.ptrTo(.u8);

    var b = Builder.init(&module);

    // func f(s: string) -> *u8 { return s.ptr; }
    // Param string → extractvalue survives (a constant string would fold).
    _ = b.beginFunction(str(&module, "dptr"), &[_]Function.Param{
        .{ .name = str(&module, "s"), .ty = .string },
    }, ptr_ty);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const s = Ref.fromIndex(0);
    const ptr = b.emit(.{ .data_ptr = .{ .operand = s } }, ptr_ty);
    b.ret(ptr, ptr_ty);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_dptr", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "extractvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret ptr") != null);
}

test "emit: array_to_slice" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const arr_ty = module.types.arrayOf(.s64, 4);
    const slice_ty = module.types.sliceOf(.s64);

    var b = Builder.init(&module);

    // func f() -> []s64 { var arr: [4]s64 = ---; return arr[:]; }
    _ = b.beginFunction(str(&module, "a2s"), &.{}, slice_ty);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const undef_arr = b.emit(.{ .const_undef = {} }, arr_ty);
    const slice = b.emit(.{ .array_to_slice = .{ .operand = undef_arr } }, slice_ty);
    b.ret(slice, slice_ty);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_a2s", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // Should have GEP for array decay + insertvalue for slice construction
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "getelementptr") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "insertvalue") != null);
}

test "emit: subslice" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const slice_ty = module.types.sliceOf(.u8);

    var b = Builder.init(&module);

    // func f(s: []u8, lo: s64, hi: s64) -> []u8 { return s[lo..hi]; }
    // All operands are params: a constant base folds the GEP, and constant
    // lo/hi fold the `hi - lo` subtraction.
    _ = b.beginFunction(str(&module, "ssfn"), &[_]Function.Param{
        .{ .name = str(&module, "s"), .ty = slice_ty },
        .{ .name = str(&module, "lo"), .ty = .s64 },
        .{ .name = str(&module, "hi"), .ty = .s64 },
    }, slice_ty);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const s = Ref.fromIndex(0);
    const lo = Ref.fromIndex(1);
    const hi = Ref.fromIndex(2);
    const sub = b.emit(.{ .subslice = .{ .base = s, .lo = lo, .hi = hi } }, slice_ty);
    b.ret(sub, slice_ty);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_subslice", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // Should have GEP for ptr+lo and sub for hi-lo
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "getelementptr") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "sub") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "insertvalue") != null);
}

// ── Optional tests ──────────────────────────────────────────────────

test "emit: optional_wrap and optional_unwrap (value type)" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const opt_ty = module.types.optionalOf(.s64);

    var b = Builder.init(&module);

    // func f(v) -> s64 { opt = wrap(v); return unwrap(opt); }
    // Param value keeps the optional non-constant (else insertvalue folds).
    _ = b.beginFunction(str(&module, "optfn"), &[_]Function.Param{
        .{ .name = str(&module, "v"), .ty = .s64 },
    }, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const val = Ref.fromIndex(0);
    const wrapped = b.optionalWrap(val, opt_ty);
    const unwrapped = b.optionalUnwrap(wrapped, .s64);
    b.ret(unwrapped, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_opt", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // wrap = insertvalue, unwrap = extractvalue
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "insertvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "extractvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i64") != null);
}

test "emit: optional_has_value" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const opt_ty = module.types.optionalOf(.s64);

    var b = Builder.init(&module);

    // Param value keeps the optional non-constant (else extractvalue folds).
    _ = b.beginFunction(str(&module, "hasfn"), &[_]Function.Param{
        .{ .name = str(&module, "v"), .ty = .s64 },
    }, .bool);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const val = Ref.fromIndex(0);
    const wrapped = b.optionalWrap(val, opt_ty);
    const has = b.optionalHasValue(wrapped);
    b.ret(has, .bool);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_has", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "extractvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "ret i1") != null);
}

// ── Switch branch test ──────────────────────────────────────────────

test "emit: switch_br" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func f(x: s64) -> s64 { match x { 0 => 10, 1 => 20, _ => 30 } }
    _ = b.beginFunction(str(&module, "swfn"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    const case0 = b.appendBlock(str(&module, "case0"), &.{});
    const case1 = b.appendBlock(str(&module, "case1"), &.{});
    const default_bb = b.appendBlock(str(&module, "default"), &.{});
    b.switchToBlock(entry);

    const x = b.constInt(1, .s64);
    const cases = alloc.dupe(inst_mod.SwitchBranch.Case, &.{
        .{ .value = 0, .target = case0, .args = &.{} },
        .{ .value = 1, .target = case1, .args = &.{} },
    }) catch unreachable;
    defer alloc.free(cases);
    b.emitVoid(.{ .switch_br = .{
        .operand = x,
        .cases = cases,
        .default = default_bb,
        .default_args = &.{},
    } }, .void);

    b.switchToBlock(case0);
    b.ret(b.constInt(10, .s64), .s64);

    b.switchToBlock(case1);
    b.ret(b.constInt(20, .s64), .s64);

    b.switchToBlock(default_bb);
    b.ret(b.constInt(30, .s64), .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_switch", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "switch") != null);
}

// ── Closure test ────────────────────────────────────────────────────

test "emit: closure_create" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    const closure_ty = module.types.closureType(&.{.s64}, .s64);

    var b = Builder.init(&module);

    // Create a dummy trampoline function
    const tramp_id = b.beginFunction(str(&module, "tramp"), &[_]inst_mod.Function.Param{
        .{ .name = str(&module, "env"), .ty = .s64 },
        .{ .name = str(&module, "x"), .ty = .s64 },
    }, .s64);
    const tramp_entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(tramp_entry);
    b.ret(b.constInt(0, .s64), .s64);
    b.finalize();

    // func f(e: *void) -> closure { return closure_create(tramp, e); }
    // A non-constant env keeps the {fn_ptr, env} aggregate non-constant so
    // the insertvalue isn't folded (a null env + constant fn_ptr would fold).
    const env_ty = module.types.ptrTo(.void);
    _ = b.beginFunction(str(&module, "mkclose"), &[_]inst_mod.Function.Param{
        .{ .name = str(&module, "e"), .ty = env_ty },
    }, closure_ty);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const cl = b.emit(.{ .closure_create = .{ .func = tramp_id, .env = Ref.fromIndex(0) } }, closure_ty);
    b.ret(cl, closure_ty);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_closure", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "insertvalue") != null);
}

// ── Box/Unbox Any test ──────────────────────────────────────────────

test "emit: box_any and unbox_any" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func f(v) -> s64 { a = box(v); return unbox(a); }
    // Param value keeps the boxed Any non-constant (else insertvalue folds).
    _ = b.beginFunction(str(&module, "anyfn"), &[_]Function.Param{
        .{ .name = str(&module, "v"), .ty = .s64 },
    }, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);

    const val = Ref.fromIndex(0);
    const boxed = b.emit(.{ .box_any = .{ .operand = val, .source_type = .s64 } }, .any);
    const unboxed = b.emit(.{ .unbox_any = .{ .operand = boxed } }, .s64);
    b.ret(unboxed, .s64);
    b.finalize();

    var emitter = LLVMEmitter.init(alloc, &module, "test_any", .{});
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "insertvalue") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "extractvalue") != null);
}

test "emit: ERR E3.0 — DWARF debug info (compile unit + subprogram + per-inst location)" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);

    // func main() -> s64 { return 42; } — with the `return` instruction
    // carrying a span that lands on line 3 of the source map below.
    _ = b.beginFunction(str(&module, "main"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);
    // "a\nb\nXYZ" — byte offset 4 ('X') is line 3, col 1.
    b.current_span = .{ .start = 4, .end = 5 };
    const c42 = b.constInt(42, .s64);
    b.ret(c42, .s64);
    b.finalize();

    // Source map keyed on the main file. setDebugContext + opt none
    // turns DWARF emission on (release opt levels skip it entirely).
    var sources = std.StringHashMap([:0]const u8).init(alloc);
    defer sources.deinit();
    try sources.put("probe.sx", "a\nb\nXYZ");

    var emitter = LLVMEmitter.init(alloc, &module, "test_dwarf", .{ .opt_level = .none });
    defer emitter.deinit();
    emitter.setDebugContext(&sources, "probe.sx");
    emitter.emit();

    try std.testing.expect(emitter.verify());

    const ir_str = emitter.dumpToString();
    // Module flags, compile unit on the main file, a subprogram for main,
    // and the return instruction's location resolved to line 3.
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "\"Debug Info Version\"") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "\"Dwarf Version\"") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "DICompileUnit") != null);
    // Regression (issue 0058): a bare filename (no directory component) must
    // still get a NON-EMPTY `directory:` — an empty `DW_AT_comp_dir` makes ld
    // silently drop the whole debug map, so the binary becomes undebuggable.
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "DIFile(filename: \"probe.sx\", directory: \".\")") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "DISubprogram(name: \"main\"") != null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "DILocation(line: 3") != null);
}

test "emit: ERR E3.0 — no DWARF without a debug context (unit-test default)" {
    const alloc = std.testing.allocator;
    var module = Module.init(alloc);
    defer module.deinit();

    var b = Builder.init(&module);
    _ = b.beginFunction(str(&module, "main"), &.{}, .s64);
    const entry = b.appendBlock(str(&module, "entry"), &.{});
    b.switchToBlock(entry);
    b.ret(b.constInt(42, .s64), .s64);
    b.finalize();

    // No setDebugContext call → no source map → debug info off even at
    // opt none. Confirms the gate keeps the metadata out by default.
    var emitter = LLVMEmitter.init(alloc, &module, "test_no_dwarf", .{ .opt_level = .none });
    defer emitter.deinit();
    emitter.emit();

    try std.testing.expect(emitter.verify());
    const ir_str = emitter.dumpToString();
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "DICompileUnit") == null);
    try std.testing.expect(std.mem.indexOf(u8, ir_str, "!dbg") == null);
}