#include <stdio.h>

#include "pre.h"
#include "codegen.h"
#include "cgC.h"
#include "ast.h"
#include "libs/stb_ds.h"

#define EMIT_SEMICOLON_NL(out) fputs(";\n", out)
#define EMIT_RB_NL(out) fputs("}\n", out)

static void
emit_expr(CodegenC *cgc, const Ast *expr);
static void
emit_expr_list(CodegenC *cgc, const Vec(Ast *) exprs, bool sep);
static void
emit_node(CodegenC *cgc, const Ast *node);

static void
indent(CodegenC *cgc)
{
#define INDENT(out) fputc('\t', out)
	switch (cgc->indent) {
	case 8: INDENT(cgc->cgctx->out); /* fallthrough */
	case 7: INDENT(cgc->cgctx->out); /* fallthrough */
	case 6: INDENT(cgc->cgctx->out); /* fallthrough */
	case 5: INDENT(cgc->cgctx->out); /* fallthrough */
	case 4: INDENT(cgc->cgctx->out); /* fallthrough */
	case 3: INDENT(cgc->cgctx->out); /* fallthrough */
	case 2: INDENT(cgc->cgctx->out); /* fallthrough */
	case 1: INDENT(cgc->cgctx->out); /* fallthrough */
	case 0: break;
	default:
		for (isize left = 0; left < cgc->indent; ++left)
			INDENT(cgc->cgctx->out);
	}
#undef INDENT
}

static void
emit_comment(CodegenC *cgc, Str comment, bool nl_after)
{
	fprintf(cgc->cgctx->out, "/* %s */%c", comment.s, nl_after ? '\n' : '\0');
}

static void
emit_include(CodegenC *cgc, Str path, bool local)
{
	fprintf(
		cgc->cgctx->out, "#include %c%s%c\n",
		local ? '"' : '<', path.s, local ? '"' : '>'
	);
}

static const char *
basic_datatype_to_c(CodegenC *cgc, const DataType *dt)
{
	switch (dt->kind) {
	case DtkBasic:
		switch (dt->size) {
		case 0: return "void";
		case 1: return "uint8_t";
		case 2: return "uint16_t";
		case 4: return "uint32_t";
		case 8: return "uint64_t";
		}
		break;
	case DtkVoid:
		return "void";
		break;
	}
	return nil;
}

static void
emit_datatype(CodegenC *cgc, const DataType *dt)
{
	switch (dt->kind) {
	case DtkBasic:
	case DtkVoid:
		fputs(basic_datatype_to_c(cgc, dt), cgc->cgctx->out);
		break;
	case DtkStruct:
		fprintf(cgc->cgctx->out, "struct %s", dt->name.s);
		break;
	}
}

static void
emit_c_attribute(CodegenC *cgc, Str attr)
{
	fprintf(cgc->cgctx->out, "__attribute((%s))", attr.s);
}

static void
emit_structdecl(CodegenC *cgc, const DataType *dt)
{
	fputs("struct %s {\n", cgc->cgctx->out);
	for (isize i = 0; i < arrlen(dt->compound.fields); ++i) {
		emit_datatype(cgc, dt->compound.fields[i]);
		EMIT_SEMICOLON_NL(cgc->cgctx->out);
	}
	fputc('}', cgc->cgctx->out);
	if (dt->compound.packed)
		emit_c_attribute(cgc, Sl("packed"));
	EMIT_SEMICOLON_NL(cgc->cgctx->out);
}

static void
emit_vardecl(CodegenC *cgc, const AstVarDecl *decl)
{
	if (decl->kind == SymConst)
		fputs("const ", cgc->cgctx->out);

	emit_datatype(cgc, decl->type);
	fprintf(cgc->cgctx->out, " %s", decl->name.s);
	if (decl->expr != nil) {
		fputc('=', cgc->cgctx->out);
		emit_expr(cgc, decl->expr);
	}
	EMIT_SEMICOLON_NL(cgc->cgctx->out);
}

static void
emit_varassign(CodegenC *cgc, const AstVarAssign *assign)
{
	fprintf(cgc->cgctx->out, "%s = ", assign->name.s);
	emit_expr(cgc, assign->expr);
	EMIT_SEMICOLON_NL(cgc->cgctx->out);
}

static void
emit_proc(CodegenC *cgc, const AstProc *proc)
{
	if (!proc->ispublic)
		fputs("static ", cgc->cgctx->out);

	if (!Str_equal(proc->name, Sl("main")))
		emit_datatype(cgc, proc->type->proc.rettype);
	else /* C main entry point special case */
		fputs("int", cgc->cgctx->out);

	fprintf(cgc->cgctx->out, " %s(", proc->name.s);

	const isize arglen = arrlen(proc->args);
	if (arglen == 0)
		fputs("void", cgc->cgctx->out);
	for (isize i = 0; i < arglen; ++i) {
		AstIdentTypePair arg = proc->args[i];
		//emit_datatype(cgc, arg.dtype);
		fputs("uint64_t ", cgc->cgctx->out);
		fputs((char *)arg.ident.s, cgc->cgctx->out);
		if (i + 1 < arglen)
			fputc(',', cgc->cgctx->out);
	}
	fputs(")\n{\n", cgc->cgctx->out);
	if (proc->body != nil)
		emit_node(cgc, proc->body);
	EMIT_RB_NL(cgc->cgctx->out);
}

static void
emit_proccall(CodegenC *cgc, const AstProcCall *call)
{
	fprintf(cgc->cgctx->out, "%s(", call->name.s);
	if (call->args != nil)
		emit_expr_list(cgc, (const Vec(Ast *))call->args->stmts, true);
	fputs(")", cgc->cgctx->out);
}

static void
emit_if(CodegenC *cgc, const AstIf *ift)
{
	fputs("if (", cgc->cgctx->out);
	emit_expr(cgc, ift->cond);
	fputs("){\n", cgc->cgctx->out);
	emit_node(cgc, ift->true_body);
	fputc('}', cgc->cgctx->out);
	if (ift->false_body != nil) {
		fputs("else", cgc->cgctx->out);
		fputs("{\n", cgc->cgctx->out);
		emit_node(cgc, ift->false_body);
		fputc('}', cgc->cgctx->out);
	}
	fputc('\n', cgc->cgctx->out);
}

static void
emit_whileLoop(CodegenC *cgc, const AstLoop *whl)
{
	fputs("while (", cgc->cgctx->out);
	emit_expr(cgc, whl->precond);
	fputs("){\n", cgc->cgctx->out);
	emit_node(cgc, whl->body);
	fputs("}\n", cgc->cgctx->out);
}

static void
emit_loop(CodegenC *cgc, const AstLoop *loop)
{
	if (loop->precond != nil)
		emit_whileLoop(cgc, loop);
	else if (loop->postcond != nil)
		unreachable();
}

static void
emit_return(CodegenC *cgc, const Ast *ret_expr)
{
	fputs("return ", cgc->cgctx->out);
	emit_expr(cgc, ret_expr);
	EMIT_SEMICOLON_NL(cgc->cgctx->out);
}

static void
emit_break(CodegenC *cgc, const Ast *unused)
{
	(void)unused;
	fputs("break;\n", cgc->cgctx->out);
}

static void
emit_discard(CodegenC *cgc, const Ast *expr)
{
	emit_node(cgc, expr);
}

static void
emit_expr_number(CodegenC *cgc, const AstNumber *num)
{
	fprintf(cgc->cgctx->out, "%lu", num->n);
}

static void
emit_expr_strlit(CodegenC *cgc, const Str *strlit)
{
	fprintf(cgc->cgctx->out, "\"%s\"", strlit->s);
}

static void
emit_expr_ident(CodegenC *cgc, const Str *ident)
{
	fputs((char *)ident->s, cgc->cgctx->out);
}

static void
emit_expr_unary(CodegenC *cgc, const AstUnary *unary)
{
	emit_expr(cgc, unary->atom);
}

static void
emit_expr_binop(CodegenC *cgc, const AstBinop *expr)
{
	/* guard binops with parenthesis, even if they are redundant */
	fputc('(', cgc->cgctx->out);
	emit_expr(cgc, expr->left);
	fputs((char *)expr->op.s, cgc->cgctx->out);
	emit_expr(cgc, expr->right);
	fputc(')', cgc->cgctx->out);
}

static void
emit_expr(CodegenC *cgc, const Ast *expr)
{
	if (expr == nil)
		return;
	switch (expr->type) {
	case AST_BINEXPR:
		emit_expr_binop(cgc, &expr->bin);
		break;
	case AST_UNARY:
		emit_expr_unary(cgc, &expr->unary);
		break;
	case AST_NUMBER:
		emit_expr_number(cgc, &expr->number);
		break;
	case AST_STRLIT:
		emit_expr_strlit(cgc, &expr->strlit);
		break;
	case AST_IDENT:
		emit_expr_ident(cgc, &expr->ident);
		break;
	case AST_PROCCALL:
		emit_proccall(cgc, &expr->call);
		break;
	default:
		unreachable();
	}
}

static void
emit_expr_list(CodegenC *cgc, const Vec(Ast *) exprs, bool sep)
{
	const isize exprs_len = arrlen(exprs);
	for (isize i = 0; i < exprs_len; ++i) {
		emit_expr(cgc, exprs[i]);
		if (sep && i + 1 < exprs_len) /* no trailling separator */
			fputc(',', cgc->cgctx->out);
	}
}

static void
emit_stmt_list(CodegenC *cgc, Vec(Ast *) stmts)
{
	for (isize i = 0; i < arrlen(stmts); ++i) {
		emit_node(cgc, stmts[i]);
	}
}

static void
emit_node(CodegenC *cgc, const Ast *node)
{
	switch (node->type) {
	case AST_STMTS:
		emit_stmt_list(cgc, node->stmts);
		break;
	case AST_PROCDEF:
		emit_proc(cgc, &node->proc);
		break;
	case AST_PROCCALL:
		emit_proccall(cgc, &node->call);
		EMIT_SEMICOLON_NL(cgc->cgctx->out);
		break;
	case AST_IF:
		emit_if(cgc, &node->ifse);
		break;
	case AST_LOOP:
		emit_loop(cgc, &node->loop);
		break;
	case AST_RETURN:
		emit_return(cgc, node->ret);
		break;
	case AST_BREAK:
		emit_break(cgc, nil);
		break;
	case AST_DISCARD:
		emit_discard(cgc, node->discard.expr);
		break;
	case AST_VARDECL:
		emit_vardecl(cgc, &node->var);
		break;
	case AST_VARASSIGN:
		emit_varassign(cgc, &node->varassgn);
		break;
	case AST_BINEXPR:
	case AST_UNARY:
	case AST_NUMBER:
	case AST_STRLIT:
	case AST_IDENT:
		emit_expr(cgc, node);
		break;
	case AST_PROCCALL_ARGS:
	case AST_EXPRS:
	case AST_INVALID:
		unreachable();
	}
}

void
cgC(CodegenC *cgc, const Ast *program)
{
	cgc->cgctx->out = stdout;

	char note_buf[255] = {0};
	snprintf(note_buf, sizeof(note_buf),
		"generated C IR from %s", cgc->cgctx->cctx->current_filename.s
	);
	emit_comment(cgc, Str_from_c(note_buf), true);

	emit_include(cgc, Sl("stdint.h"), false);
	fputc('\n', cgc->cgctx->out);
	emit_node(cgc, program);
}