/* SPDX-License-Identifier: copyleft-next-0.3.1 */
/* Copyright 2024 Kim Kuparinen < kimi.h.kuparinen@gmail.com > */

#include <fwd/analyze.h>
#include <assert.h>

struct state {
};

static int analyze(struct state *state, struct scope *scope, struct ast *node);
static int analyze_list(struct state *state, struct scope *scope, struct ast *nodes);

static int analyze_type(struct state *state, struct scope *scope, struct type *type);
static int analyze_type_list(struct state *state, struct scope *scope, struct type *types);

static int analyze_proc(struct state *state, struct scope *scope, struct ast *node)
{
	(void)state;
	(void)scope;

	struct scope *proc_scope = create_scope();
	if (!proc_scope) {
		internal_error("failed allocating proc scope");
		return -1;
	}

	scope_add_scope(scope, proc_scope);

	struct state proc_state = {};
	if (analyze_list(&proc_state, proc_scope, proc_params(node)))
		return -1;

	struct type *callable = tgen_callable(NULL, node->loc);
	if (!callable) {
		internal_error("failed allocating proc type");
		return -1;
	}

	foreach_node(param, proc_params(node)) {
		type_append(&callable->t0, clone_type(param->t));
	}

	node->t = callable;

	return analyze(&proc_state, proc_scope, proc_body(node));
}

static int analyze_unop(struct state *state, struct scope *scope, struct ast *node)
{
	assert(false);
	return 0;
}

static int analyze_block(struct state *state, struct scope *scope, struct ast *node)
{
	struct scope *block_scope = create_scope();
	if (!block_scope) {
		internal_error("failed to allocate block scope");
		return -1;
	}

	scope_add_scope(scope, block_scope);
	if (analyze_list(state, block_scope, block_body(node)))
		return -1;

	node->t = ast_last(block_body(node))->t;
	return 0;
}

static int analyze_var(struct state *state, struct scope *scope, struct ast *node)
{
	if (analyze_type(state, scope, var_type(node)))
		return -1;

	node->t = var_type(node);
	return scope_add_var(scope, node);
}

static int analyze_let(struct state *state, struct scope *scope, struct ast *node)
{
	if (analyze(state, scope, let_var(node)))
		return -1;

	if (analyze(state, scope, let_expr(node)))
		return -1;

	struct type *l = (let_var(node))->t;
	struct type *r = (let_expr(node))->t;
	if (!types_match(l, r)) {
		type_mismatch(scope, node, l, r);
		return -1;
	}

	node->t = l;
	return 0;
}

static int analyze_init(struct state *state, struct scope *scope, struct ast *node)
{
	if (analyze_type_list(state, scope, init_args(node)))
		return -1;

	if (analyze(state, scope, init_body(node)))
		return -1;

	/** @todo check that all parameters match, though that requires that the
	 * type is defined in fwd and not in C++, so this might have to wait a
	 * bit */
	node->t = tgen_construct(init_id(node), init_args(node), node->loc);
	if (!node->t) {
		internal_error("failed allocating type for construct");
		return -1;
	}

	return 0;
}

static int analyze_call(struct state *state, struct scope *scope, struct ast *node)
{
	struct ast *expr = call_expr(node);
	if (analyze(state, scope, expr))
		return -1;

	if (!is_callable(expr->t)) {
		semantic_error(scope, node, "expected callable expression");
		return -1;
	}

	struct type *types = callable_types(expr->t);
	struct ast *args = call_args(node);
	if (analyze_list(state, scope, args))
		return -1;

	size_t expected = type_list_len(types);
	size_t got = ast_list_len(args);
	if (expected != got) {
		semantic_error(scope, node, "expected %d params, got %d", expected, got);
		return -1;
	}

	struct type *type = types;
	foreach_node(arg, args) {
		if (!types_match(type, arg->t)) {
			type_mismatch(scope, node, type, arg->t);
			return -1;
		}

		type = type->n;
	}

	node->t = tgen_void(node->loc);
	if (!node->t) {
		internal_error("failed allocating void type for call");
		return -1;
	}

	return 0;
}

static int analyze_id(struct state *state, struct scope *scope, struct ast *node)
{
	struct ast *found = file_scope_find_symbol(scope, id_str(node));
	if (!found) {
		semantic_error(scope, node, "no symbol named \"%s\"", id_str(node));
		return -1;
	}

	/* kind of hacky, functions are given their type before they've been
	 * analyzed fully, this enables recursion */
	if (!found->t && !ast_flags(found, AST_FLAG_ANALYZED)) {
		assert(found->k == AST_PROC_DEF);
		/* a proc def will use its own state and scope, but pass these
		 * on in case the analysis wants to print errors or something
		 */
		if (analyze(state, scope, found))
			return -1;
	}

	node->t = found->t;
	return 0;
}

static int analyze_closure(struct state *state, struct scope *scope, struct ast *node)
{
	struct scope *closure_scope = create_scope();
	if (!closure_scope) {
		internal_error("failed allocating closure scope");
		return -1;
	}

	scope_add_scope(scope, closure_scope);

	if (analyze_list(state, closure_scope, closure_bindings(node)))
		return -1;

	if (analyze(state, closure_scope, closure_body(node)))
		return -1;

	struct type *callable = tgen_callable(NULL, node->loc);
	if (!callable) {
		internal_error("failed allocating closure type");
		return -1;
	}

	/** @todo use analysis to figure out if this closure can be called
	 * multiple times or just once */

	foreach_node(binding, closure_bindings(node)) {
		type_append(&callable->t0, clone_type(binding->t));
	}

	node->t = callable;
	return 0;
}

static int analyze(struct state *state, struct scope *scope, struct ast *node)
{
	if (!node)
		return 0;

	if (ast_flags(node, AST_FLAG_ANALYZED)) {
		assert(node->t);
		return 0;
	}

	if (ast_flags(node, AST_FLAG_PREANALYZIS)) {
		semantic_error(scope, node, "semantic loop detected");
		return -1;
	}

	ast_set_flags(node, AST_FLAG_PREANALYZIS);

	if (!node->scope)
		node->scope = scope;

	int ret = 0;
	if (is_unop(node)) {
		ret = analyze_unop(state, scope, node);
		goto out;
	}

	switch (node->k) {
	case AST_PROC_DEF:	ret = analyze_proc	(state, scope, node); break;
	case AST_VAR_DEF:	ret = analyze_var	(state, scope, node); break;
	case AST_BLOCK:		ret = analyze_block	(state, scope, node); break;
	case AST_LET:		ret = analyze_let	(state, scope, node); break;
	case AST_INIT:		ret = analyze_init	(state, scope, node); break;
	case AST_CALL:		ret = analyze_call	(state, scope, node); break;
	case AST_ID:		ret = analyze_id	(state, scope, node); break;
	case AST_CLOSURE:	ret = analyze_closure	(state, scope, node); break;
	default:
		   internal_error("missing ast analysis");
		   return -1;
	}

out:
	if (ret)
		return ret;

	assert(node->t);
	assert(node->scope);
	ast_set_flags(node, AST_FLAG_ANALYZED);
	return 0;
}

static int analyze_list(struct state *state, struct scope *scope, struct ast *nodes)
{
	foreach_node(node, nodes) {
		if (analyze(state, scope, node))
			return -1;
	}

	return 0;
}

static int analyze_type(struct state *state, struct scope *scope, struct type *type)
{
	/* for now, let's just say all types are fine as they are, specified by
	 * the user. */
	(void)state;
	(void)scope;
	(void)type;
	return 0;
}

static int analyze_type_list(struct state *state, struct scope *scope, struct type *types)
{
	foreach_type(type, types) {
		if (analyze_type(state, scope, type))
			return -1;
	}

	return 0;
}

int analyze_root(struct scope *scope, struct ast *root)
{
	foreach_node(node, root) {
		assert(node->k == AST_PROC_DEF);
		if (scope_add_proc(scope, node))
			return -1;
	}

	foreach_node(node, root) {
		struct state state = {};
		if (analyze(&state, scope, node))
			return -1;
	}

	return 0;
}