/*
 * type.c — Type values and structural equality.
 *
 * Built-in types are constructed once and exposed as globals so the
 * rest of the compiler can `==`-compare them. Compound types (ptr,
 * slice, array, fn, struct, chan) are constructed on demand and
 * de-duplicated when equality is cheap (only ptr/slice for now).
 */
#include "ww.h"
#include <string.h>

Type	*ty_void, *ty_bool, *ty_rune;
Type	*ty_i8, *ty_i16, *ty_i32, *ty_i64;
Type	*ty_u8, *ty_u16, *ty_u32, *ty_u64;
Type	*ty_int, *ty_uint, *ty_uintptr;
Type	*ty_f32, *ty_f64, *ty_str;
Type	*ty_err;
Type	*ty_never;
Type	*ty_untyped_int, *ty_untyped_float, *ty_untyped_str;
Type	*ty_untyped_rune, *ty_untyped_bool, *ty_untyped_nil;

Type *
newtype(Arena *a, TypeKind k)
{
	Type *t = amalloc(a, sizeof *t);
	t->kind = k;
	return t;
}

static Type *
prim(Arena *a, TypeKind k, const char *nm, u64 sz, u64 al)
{
	Type *t = newtype(a, k);
	t->name = nm;
	t->size = sz;
	t->align = al ? al : sz;
	return t;
}

void
typesinit(Arena *a)
{
	/* Always re-init: callers create a fresh arena per compilation unit
	 * and free it; old globals point at freed memory. */
	ty_void   = prim(a, TY_VOID,   "void",    0, 1);
	ty_bool   = prim(a, TY_BOOL,   "bool",    1, 1);
	ty_rune   = prim(a, TY_RUNE,   "rune",    4, 4);

	ty_i8     = prim(a, TY_I8,     "i8",      1, 1);
	ty_i16    = prim(a, TY_I16,    "i16",     2, 2);
	ty_i32    = prim(a, TY_I32,    "i32",     4, 4);
	ty_i64    = prim(a, TY_I64,    "i64",     8, 8);
	ty_u8     = prim(a, TY_U8,     "u8",      1, 1);
	ty_u16    = prim(a, TY_U16,    "u16",     2, 2);
	ty_u32    = prim(a, TY_U32,    "u32",     4, 4);
	ty_u64    = prim(a, TY_U64,    "u64",     8, 8);
	ty_int    = prim(a, TY_INT,    "int",     8, 8);   /* amd64 */
	ty_uint   = prim(a, TY_UINT,   "uint",    8, 8);
	ty_uintptr= prim(a, TY_UINTPTR,"uintptr", 8, 8);
	ty_f32    = prim(a, TY_F32,    "f32",     4, 4);
	ty_f64    = prim(a, TY_F64,    "f64",     8, 8);
	/* str is { *u8, len } — 16 bytes on amd64. ABI: pointer + u64. */
	ty_str    = prim(a, TY_STR,    "str",    16, 8);
	ty_err    = prim(a, TY_ERR,    "<err>",   0, 1);
	ty_never  = prim(a, TY_NEVER,  "never",   0, 1);

	ty_untyped_int   = prim(a, TY_UNTYPED_INT,   "untyped_int",   0, 1);
	ty_untyped_float = prim(a, TY_UNTYPED_FLOAT, "untyped_float", 0, 1);
	ty_untyped_str   = prim(a, TY_UNTYPED_STR,   "untyped_str",   0, 1);
	ty_untyped_rune  = prim(a, TY_UNTYPED_RUNE,  "untyped_rune",  0, 1);
	ty_untyped_bool  = prim(a, TY_UNTYPED_BOOL,  "untyped_bool",  0, 1);
	ty_untyped_nil   = prim(a, TY_UNTYPED_NIL,   "untyped_nil",   0, 1);
}

Type *
type_ptr(Arena *a, Type *sub)
{
	Type *t = newtype(a, TY_PTR);
	t->sub = sub;
	t->size = 8;
	t->align = 8;
	return t;
}

Type *
type_slice(Arena *a, Type *sub)
{
	Type *t = newtype(a, TY_SLICE);
	t->sub = sub;
	t->size = 24;	/* { *T, len, cap } */
	t->align = 8;
	return t;
}

Type *
type_array(Arena *a, Type *sub, u64 len)
{
	Type *t = newtype(a, TY_ARRAY);
	t->sub = sub;
	t->alen = len;
	t->size = sub ? sub->size * len : 0;
	t->align = sub ? sub->align : 1;
	return t;
}

Type *
type_chan(Arena *a, Type *sub)
{
	Type *t = newtype(a, TY_CHAN);
	t->sub = sub;
	t->size = 8;	/* opaque ptr */
	t->align = 8;
	return t;
}

Type *
type_named(Arena *a, const char *name, Type *under)
{
	Type *t = newtype(a, TY_NAMED);
	t->name = name;
	t->under = under;
	if (under) {
		t->size = under->size;
		t->align = under->align;
		t->iserror = under->iserror;
	}
	return t;
}

int
type_isint(Type *t)
{
	if (t == NULL) return 0;
	switch (t->kind) {
	case TY_I8: case TY_I16: case TY_I32: case TY_I64:
	case TY_U8: case TY_U16: case TY_U32: case TY_U64:
	case TY_INT: case TY_UINT: case TY_UINTPTR:
	case TY_RUNE:
	case TY_UNTYPED_INT:
	case TY_UNTYPED_RUNE:
		return 1;
	case TY_ENUM:	return type_isint(t->sub);
	case TY_NAMED:	return type_isint(t->under);
	default:	return 0;
	}
}

int
type_isfloat(Type *t)
{
	if (t == NULL) return 0;
	switch (t->kind) {
	case TY_F32: case TY_F64: case TY_UNTYPED_FLOAT:
		return 1;
	case TY_NAMED: return type_isfloat(t->under);
	default: return 0;
	}
}

int
type_isnum(Type *t)
{
	return type_isint(t) || type_isfloat(t);
}

int
type_isunsigned(Type *t)
{
	if (t == NULL) return 0;
	switch (t->kind) {
	case TY_U8: case TY_U16: case TY_U32: case TY_U64:
	case TY_UINT: case TY_UINTPTR:
		return 1;
	case TY_NAMED: return type_isunsigned(t->under);
	default: return 0;
	}
}

int
type_isuntyped(Type *t)
{
	if (t == NULL) return 0;
	switch (t->kind) {
	case TY_UNTYPED_INT: case TY_UNTYPED_FLOAT: case TY_UNTYPED_STR:
	case TY_UNTYPED_RUNE: case TY_UNTYPED_BOOL: case TY_UNTYPED_NIL:
		return 1;
	default: return 0;
	}
}

Type *
type_default(Type *t)
{
	if (t == NULL) return NULL;
	switch (t->kind) {
	case TY_UNTYPED_INT:	return ty_i32;
	case TY_UNTYPED_FLOAT:	return ty_f64;
	case TY_UNTYPED_STR:	return ty_str;
	case TY_UNTYPED_RUNE:	return ty_rune;
	case TY_UNTYPED_BOOL:	return ty_bool;
	case TY_UNTYPED_NIL:	return NULL;	/* needs context */
	default: return t;
	}
}

int
type_eq(Type *a, Type *b)
{
	if (a == b) return 1;
	if (a == NULL || b == NULL) return 0;
	if (a->kind != b->kind) return 0;
	switch (a->kind) {
	case TY_PTR: case TY_SLICE: case TY_CHAN:
		return type_eq(a->sub, b->sub);
	case TY_ARRAY:
		return a->alen == b->alen && type_eq(a->sub, b->sub);
	case TY_FN: {
		if (a->variadic != b->variadic) return 0;
		if (!type_eq(a->ret, b->ret)) return 0;
		Tparam *pa = a->params, *pb = b->params;
		while (pa && pb) {
			if (pa->variadic != pb->variadic) return 0;
			if (!type_eq(pa->type, pb->type)) return 0;
			pa = pa->next; pb = pb->next;
		}
		return pa == NULL && pb == NULL;
	}
	case TY_STRUCT: {
		Tfield *fa = a->fields, *fb = b->fields;
		while (fa && fb) {
			if (strcmp(fa->name, fb->name) != 0) return 0;
			if (!type_eq(fa->type, fb->type)) return 0;
			fa = fa->next; fb = fb->next;
		}
		return fa == NULL && fb == NULL;
	}
	case TY_NAMED:
		return a == b;	/* nominally equal only when same node */
	case TY_TUPLE: {
		Tparam *pa = a->params, *pb = b->params;
		while (pa && pb) {
			if (!type_eq(pa->type, pb->type)) return 0;
			pa = pa->next; pb = pb->next;
		}
		return pa == NULL && pb == NULL;
	}
	case TY_TAGGED: {
		/* Tagged unions are structurally equal iff variant lists
		 * match position-by-position. Nullable fold is a per-Type
		 * flag, so equal-up-to-fold types compare not-equal here —
		 * the caller can unwrap intentionally if needed. */
		if (a->nullable != b->nullable) return 0;
		Tparam *pa = a->params, *pb = b->params;
		while (pa && pb) {
			if (!type_eq(pa->type, pb->type)) return 0;
			pa = pa->next; pb = pb->next;
		}
		return pa == NULL && pb == NULL;
	}
	default: return 1;	/* primitives */
	}
}

int
type_assignable(Type *dst, Type *src)
{
	if (dst == NULL || src == NULL) return 0;
	if (dst == ty_err || src == ty_err) return 1;	/* swallow */
	if (src == ty_never) return 1;	/* bottom flows into anything */
	if (type_eq(dst, src)) return 1;

	/* Tagged-union assignment:
	 *   - concrete → tagged: src must match one of dst's variants.
	 *   - tagged → tagged: src is assignable when every variant of
	 *     src appears as a variant of dst (Hare-style subset). Tag
	 *     remap at the use site handles different variant indices.
	 * Checked before the untyped branch so untyped literals flow
	 * through to a variant's typed slot. Unwraps a NAMED alias on
	 * either side so `type result = (T|E);` accepts variants too. */
	{
		Type *du = (dst->kind == TY_NAMED) ? dst->under : dst;
		Type *su = (src->kind == TY_NAMED) ? src->under : src;
		if (du && du->kind == TY_TAGGED &&
		    !(su && su->kind == TY_TAGGED)) {
			for (Tparam *p = du->params; p; p = p->next)
				if (type_assignable(p->type, src)) return 1;
			return 0;
		}
		if (du && du->kind == TY_TAGGED &&
		    su && su->kind == TY_TAGGED) {
			for (Tparam *sp = su->params; sp; sp = sp->next) {
				int ok = 0;
				for (Tparam *dp = du->params; dp; dp = dp->next)
					if (type_eq(dp->type, sp->type)) {
						ok = 1; break;
					}
				if (!ok) return 0;
			}
			return 1;
		}
	}

	/* Untyped → typed: only if the typed kind can hold the value. */
	if (type_isuntyped(src)) {
		if (src->kind == TY_UNTYPED_INT && type_isnum(dst)) return 1;
		if (src->kind == TY_UNTYPED_FLOAT && type_isfloat(dst)) return 1;
		if (src->kind == TY_UNTYPED_STR && (dst->kind == TY_STR ||
		    (dst->kind == TY_NAMED && dst->under && dst->under->kind == TY_STR))) return 1;
		if (src->kind == TY_UNTYPED_RUNE && (type_isint(dst) || dst->kind == TY_RUNE)) return 1;
		if (src->kind == TY_UNTYPED_BOOL && (dst->kind == TY_BOOL ||
		    (dst->kind == TY_NAMED && dst->under && dst->under->kind == TY_BOOL))) return 1;
		if (src->kind == TY_UNTYPED_NIL) {
			Type *du = (dst->kind == TY_NAMED) ? dst->under : dst;
			if (du && (du->kind == TY_PTR || du->kind == TY_SLICE ||
			    du->kind == TY_CHAN || du->kind == TY_FN))
				return 1;
		}
		return 0;
	}

	/* Named on either side: compare to the underlying. NAMED is a
	 * distinct type from its under; but assignment from under to
	 * named (and vice-versa) is allowed in this minimal checker. */
	if (dst->kind == TY_NAMED && type_eq(dst->under, src)) return 1;
	if (src->kind == TY_NAMED && type_eq(dst, src->under)) return 1;

	/* Tuple-to-tuple: element-wise assignable. */
	if (dst->kind == TY_TUPLE && src->kind == TY_TUPLE) {
		Tparam *pa = dst->params, *pb = src->params;
		while (pa && pb) {
			if (!type_assignable(pa->type, pb->type)) return 0;
			pa = pa->next; pb = pb->next;
		}
		return pa == NULL && pb == NULL;
	}

	return 0;
}

const char *
type_name(Arena *a, Type *t)
{
	if (t == NULL) return "<nil>";
	switch (t->kind) {
	case TY_NONE:		return "<none>";
	case TY_VOID:		return "void";
	case TY_BOOL:		return "bool";
	case TY_RUNE:		return "rune";
	case TY_I8:		return "i8";
	case TY_I16:		return "i16";
	case TY_I32:		return "i32";
	case TY_I64:		return "i64";
	case TY_U8:		return "u8";
	case TY_U16:		return "u16";
	case TY_U32:		return "u32";
	case TY_U64:		return "u64";
	case TY_INT:		return "int";
	case TY_UINT:		return "uint";
	case TY_UINTPTR:	return "uintptr";
	case TY_F32:		return "f32";
	case TY_F64:		return "f64";
	case TY_STR:		return "str";
	case TY_ERR:		return "<err>";
	case TY_NEVER:		return "never";
	case TY_UNTYPED_INT:	return "untyped_int";
	case TY_UNTYPED_FLOAT:	return "untyped_float";
	case TY_UNTYPED_STR:	return "untyped_str";
	case TY_UNTYPED_RUNE:	return "untyped_rune";
	case TY_UNTYPED_BOOL:	return "untyped_bool";
	case TY_UNTYPED_NIL:	return "untyped_nil";
	case TY_PTR:		return aprintf(a, "*%s", type_name(a, t->sub));
	case TY_SLICE:		return aprintf(a, "[]%s", type_name(a, t->sub));
	case TY_ARRAY:		return aprintf(a, "[%llu]%s",
				    (unsigned long long)t->alen, type_name(a, t->sub));
	case TY_CHAN:		return aprintf(a, "chan %s", type_name(a, t->sub));
	case TY_FN: {
		const char *r = t->ret ? type_name(a, t->ret) : "void";
		const char *acc = "";
		for (Tparam *p = t->params; p; p = p->next) {
			const char *pn = type_name(a, p->type);
			acc = acc[0] ? aprintf(a, "%s, %s", acc, pn) : pn;
		}
		return aprintf(a, "fn(%s) %s", acc, r);
	}
	case TY_STRUCT:		return t->name ? t->name : "struct{...}";
	case TY_NAMED:		return t->name ? t->name : "<named>";
	case TY_TUPLE: {
		const char *acc = "";
		for (Tparam *p = t->params; p; p = p->next) {
			const char *pn = type_name(a, p->type);
			acc = acc[0] ? aprintf(a, "%s, %s", acc, pn) : pn;
		}
		return aprintf(a, "(%s)", acc);
	}
	case TY_TAGGED: {
		const char *acc = "";
		for (Tparam *p = t->params; p; p = p->next) {
			const char *pn = type_name(a, p->type);
			acc = acc[0] ? aprintf(a, "%s | %s", acc, pn) : pn;
		}
		return aprintf(a, "(%s)", acc);
	}
	case TY_ENUM:
		return aprintf(a, "enum %s",
		    t->sub ? type_name(a, t->sub) : "i32");
	}
	return "?";
}