/* Oort
 * Copyright 2007, Soren Sandmann Pedersen
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include "ast.h"

static symbol_table_t *
symbol_table_new (symbol_table_t *outer)
{
    symbol_table_t *table = g_new0 (symbol_table_t, 1);

    table->outer = outer;
    table->symbols = g_hash_table_new (g_str_hash, g_str_equal);

    return table;
}

static gboolean
symbol_table_insert (symbol_table_t   *table,
		     const char       *name,
		     gpointer          value)
{
    if (g_hash_table_lookup (table->symbols, name))
	return FALSE;

    g_hash_table_insert (table->symbols, g_strdup (name), value);
    return TRUE;
}

static gpointer
symbol_table_lookup (symbol_table_t *table,
		     const char *key)
{
    while (table)
    {
	gpointer result = g_hash_table_lookup (table->symbols, key);

	if (result)
	    return result;

	table = table->outer;
    }

    return NULL;
}

/*
 * First pass to gather definitions so we can support mutual recursion
 */
static symbol_table_t *
find_outer_table (ast_t *ast)
{
    if (!ast)
	return NULL;

    if (ast->common.type == AST_PROGRAM)
	return ast->program.symbol_table;
    else if (ast_is (ast, AST_DEFINITION, AST_FUNCTION_DEFINITION))
	return ast->definition.function.symbol_table;
    else if (ast_is (ast, AST_STATEMENT, AST_BLOCK_STATEMENT))
	return ast->statement.block.symbol_table;
    else if (ast_is (ast, AST_EXPRESSION, AST_BLOCK_EXPRESSION))
	return ast->expression.block.symbol_table;
    else if (ast_is (ast, AST_DEFINITION, AST_CLASS_DEFINITION))
	return ast->definition.class.symbol_table;
    else
	return find_outer_table (ast->common.parent);
}

static gboolean
already_defined (const char *name)
{
    return report_error ("name %s is already defined\n", name);
}

static gboolean
symbol_pass1 (ast_t *ast)
{
    GList *list;
    symbol_table_t *table = (void *)find_outer_table (ast->common.parent);

    if (ast_is (ast, AST_DEFINITION, AST_FUNCTION_DEFINITION))
    {
	ast_function_definition_t *function = &ast->definition.function;

	if (!symbol_table_insert (table, function->name,
				  (ast_definition_t *)function))
	{
	    return already_defined (function->name);
	}

	function->symbol_table = symbol_table_new (table);
    }
    else if (ast_is (ast, AST_DEFINITION, AST_CLASS_DEFINITION))
    {
	ast_class_definition_t *class = &ast->definition.class;

	if (!symbol_table_insert (table, class->name,
				  (ast_definition_t *)class))
	{
	    return already_defined (class->name);
	}

	class->symbol_table = symbol_table_new (table);
    }
    else if (ast_is (ast, AST_DEFINITION, AST_TYPE_DEFINITION))
    {
	ast_type_definition_t *type = &ast->definition.type;

	if (!symbol_table_insert (table, type->name,
				  (ast_definition_t *)type))
	{
	    return already_defined (type->name);
	}
    }
    else if (ast_is (ast, AST_STATEMENT, AST_LABEL_STATEMENT))
    {
	ast_label_statement_t *label = &ast->statement.label;
	ast_t *a;

	/* Labels have function scope or, if they are not in a function,
	 * program scope, so we need a special-cased lookup here.
	 */
	a = ast->common.parent;
	for (;;)
	{
	    if (a->common.type == AST_PROGRAM)
	    {
		table = a->program.symbol_table;
		break;
	    }
	    else if (ast_is (a, AST_DEFINITION, AST_FUNCTION_DEFINITION))
	    {
		table = a->definition.function.symbol_table;
		break;
	    }

	    a = a->common.parent;
	}

	if (!symbol_table_insert (table, label->label, label->definition))
	    return report_error ("label %s already defined\n", label->label);
    }
    else if (ast_is (ast, AST_STATEMENT, AST_BLOCK_STATEMENT))
    {
	ast_block_statement_t *block = &ast->statement.block;

	block->symbol_table = symbol_table_new (table);
    }
    else if (ast_is (ast, AST_EXPRESSION, AST_BLOCK_EXPRESSION))
    {
	ast_block_expression_t *block = &ast->expression.block;

	block->symbol_table = symbol_table_new (table);
    }

    for (list = ast->common.children->head; list; list = list->next)
    {
	if (!symbol_pass1 (list->data))
	    return FALSE;
    }

    return TRUE;
}

/*
 * Second pass to check that variables are defined
 */
static gboolean
symbol_pass2 (ast_t *ast)
{
    symbol_table_t *table = find_outer_table (ast);
    GList *list;

    if (ast_is (ast, AST_DEFINITION, AST_VARIABLE_DEFINITION))
    {
	ast_definition_t *definition = &ast->definition;

	if (!symbol_table_insert (table, definition->variable.name,
				  definition))
	{
	    return report_error ("%s already defined\n",
				 definition->variable.name);
	}
    }
    else if (ast_is (ast, AST_EXPRESSION, AST_IDENTIFIER_EXPRESSION))
    {
	ast_identifier_expression_t *id = &ast->expression.identifier;
	ast_definition_t *definition =
	    symbol_table_lookup (table, id->name);

	if (!definition)
	    return report_error ("Undefined variable %s\n", id->name);

	id->definition = definition;
    }
    else if (ast_is (ast, AST_TYPE_SPEC, AST_IDENTIFIER_TYPE))
    {
	ast_identifier_type_spec_t *id = &ast->type_spec.identifier;
	ast_definition_t *definition =
	    symbol_table_lookup (table, id->name);

	if (!definition)
	    return report_error ("Undefined type name %s\n", id->name);

	if (definition->common.type != AST_CLASS_DEFINITION &&
	    definition->common.type != AST_TYPE_DEFINITION)
	{
	    return report_error ("%s is not a type name\n", id->name);
	}

	id->definition = definition;
    }

    for (list = ast->common.children->head; list; list = list->next)
    {
	if (!symbol_pass2 (list->data))
	    return FALSE;
    }

    return TRUE;
}

gboolean
symbol (ast_t *ast)
{
    ast->program.symbol_table = symbol_table_new (NULL);

    if (!symbol_pass1 (ast))
	return FALSE;

    if (!symbol_pass2 (ast))
	return FALSE;

    return TRUE;
}