/*
	switch.c

	qc switch statement support

	Copyright (C) 2001 Bill Currie <bill@taniwha.org>

	Author: Bill Currie <bill@taniwha.org>
	Date: 2001/10/24

	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:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

*/
static const char rcsid[] =
	"$Id$";

#include <QF/hash.h>
#include <QF/sys.h>

#include "qfcc.h"
#include "switch.h"
#include "scope.h"
#include "qc-parse.h"

typedef struct case_node_s {
	expr_t     *low;
	expr_t     *high;
	expr_t    **labels;
	expr_t     *_label;
	struct case_node_s *left, *right;
} case_node_t;

static unsigned long
get_hash (void *_cl, void *unused)
{
	case_label_t *cl = (case_label_t *) _cl;

	return cl->value ? cl->value->e.integer_val : 0;
}

static int
compare (void *_cla, void *_clb, void *unused)
{
	case_label_t *cla = (case_label_t *) _cla;
	case_label_t *clb = (case_label_t *) _clb;
	expr_t     *v1 = cla->value;
	expr_t     *v2 = clb->value;

	if (v1 == v2)
		return 1;
	if ((v1 && !v2) || (!v1 && v2))
		return 0;
	return v1->e.integer_val == v2->e.integer_val;
}

struct expr_s *
case_label_expr (switch_block_t *switch_block, expr_t *value)
{
	case_label_t *cl = malloc (sizeof (case_label_t));

	if (!cl)
		Sys_Error ("case_label_expr: Memory Allocation Failure\n");

	if (value && value->type < ex_string) {
		error (value, "non-constant case value");
		free (cl);
		return 0;
	}
	if (!switch_block) {
		error (value, "%s outside of switch", value ? "case" : "default");
		free (cl);
		return 0;
	}
	cl->value = value;
	if (Hash_FindElement (switch_block->labels, cl)) {
		error (value, "duplicate %s", value ? "case" : "default");
		free (cl);
		return 0;
	}
	cl->label = new_label_expr ();
	Hash_AddElement (switch_block->labels, cl);
	return cl->label;
}

switch_block_t *
new_switch_block (void)
{
	switch_block_t *switch_block = malloc (sizeof (switch_block_t));

	if (!switch_block)
		Sys_Error ("new_switch_block: Memory Allocation Failure\n");
	switch_block->labels = Hash_NewTable (127, 0, 0, 0);
	Hash_SetHashCompare (switch_block->labels, get_hash, compare);
	switch_block->test = 0;
	return switch_block;
}

static int
label_compare (const void *_a, const void *_b)
{
	const case_label_t **a = (const case_label_t **) _a;
	const case_label_t **b = (const case_label_t **) _b;
	const char *s1, *s2;

	switch ((*a)->value->type) {
		case ex_string:
			s1 = (*a)->value->e.string_val ? (*a)->value->e.string_val : "";
			s2 = (*b)->value->e.string_val ? (*b)->value->e.string_val : "";
			return strcmp (s1, s2);
			break;
		case ex_float:
			return (*a)->value->e.float_val - (*b)->value->e.float_val;
			break;
		case ex_integer:
			return (*a)->value->e.integer_val - (*b)->value->e.integer_val;
			break;
		default:
			error (0, "internal compiler error in switch");
			abort ();
	}
}

static case_node_t *
new_case_node (expr_t *low, expr_t *high)
{
	case_node_t *node = malloc (sizeof (case_node_t));

	if (!node)
		Sys_Error ("out of memory");
	node->low = low;
	node->high = high;
	if (low == high) {
		node->labels = &node->_label;
		node->_label = 0;
	} else {
		int         size;

		if (low->type != ex_integer) {
			error (low, "switch: internal error");
			abort ();
		}
		size = high->e.integer_val - low->e.integer_val + 1;
		node->labels = calloc (size, sizeof (case_node_t *));
	}
	node->left = node->right = 0;
	return node;
}

static case_node_t *
balance_case_tree (case_node_t **nodes, int base, int count)
{
	case_node_t *node;
	int         index = count / 2;

	if (!count)
		return 0;

	node = nodes[base + index];

	node->left = balance_case_tree (nodes, base, index);

	base += index + 1;
	count -= index + 1;
	node->right = balance_case_tree (nodes, base, count);

	return node;
}

static case_node_t *
build_case_tree (case_label_t **labels, int count, int range)
{
	case_node_t **nodes;
	int         i, j, k;
	int         num_nodes = 0;

	qsort (labels, count, sizeof (*labels), label_compare);

	nodes = (case_node_t **) malloc (count * sizeof (case_node_t *));

	if (!nodes)
		Sys_Error ("out of memory");

	if (range && labels[0]->value->type == ex_integer) {
		for (i = 0; i < count - 1; i = j, num_nodes++) {
			for (j = i + 1; j < count; j++) {
				if (labels[j]->value->e.integer_val
					- labels[j - 1]->value->e.integer_val > 1)
					break;
			}
			nodes[num_nodes] = new_case_node (labels[i]->value,
											  labels[j - 1]->value);
			for (k = i; k < j; k++)
				nodes[num_nodes]->labels[labels[k]->value->e.integer_val
										 - labels[i]->value->e.integer_val]
					= labels[k]->label;
		}
		if (i < count) {
			nodes[num_nodes] = new_case_node (labels[i]->value,
											  labels[i]->value);
			nodes[num_nodes]->labels[0] = labels[i]->label;
			num_nodes++;
		}
	} else {
		for (i = 0; i < count; i++, num_nodes++) {
			nodes[num_nodes] = new_case_node (labels[i]->value,
											  labels[i]->value);
			nodes[num_nodes]->labels[0] = labels[i]->label;
		}
	}
	return balance_case_tree (nodes, 0, num_nodes);
}

static void
build_switch (expr_t *sw, case_node_t *tree, int op, expr_t *sw_val,
			  expr_t *temp, expr_t *default_label)
{
	expr_t     *test;
	expr_t     *branch;
	expr_t     *high_label = default_label;
	expr_t     *low_label = default_label;

	if (!tree) {
		branch = new_unary_expr ('g', default_label);
		append_expr (sw, branch);
		return;
	}

	if (tree->right) {
		high_label = new_label_expr ();
	}
	if (tree->left) {
		low_label = new_label_expr ();
	}

	test = binary_expr (op, sw_val, tree->low);

	test = assign_expr (temp, test);
	append_expr (sw, test);

	if (tree->low == tree->high) {
		branch = new_binary_expr ('n', temp, tree->labels[0]);
		append_expr (sw, branch);

		if (tree->left) {
			branch = new_binary_expr (IFA, temp, high_label);
			append_expr (sw, branch);

			build_switch (sw, tree->left, op, sw_val, temp, default_label);

			if (tree->right)
				append_expr (sw, high_label);
		}
		if (tree->right || !tree->left) {
			build_switch (sw, tree->right, op, sw_val, temp, default_label);
		}
	} else {
		expr_t     *utemp = new_temp_def_expr (&type_uinteger);
		int         low = tree->low->e.integer_val;
		int         high = tree->high->e.integer_val;
		def_t      *def;
		expr_t     *table = new_expr ();
		const char *name = new_label_name ();
		int         i;
		expr_t     *range = binary_expr ('-', tree->high, tree->low);

		range->type = ex_uinteger;

		def = PR_GetArray (&type_uinteger, name, high - low + 1, 0,
						   &numpr_globals);
		table->type = ex_def;
		table->e.def = def;

		if (tree->left) {
			branch = new_binary_expr (IFB, temp, low_label);
			append_expr (sw, branch);
		}
		append_expr (sw, new_bind_expr (temp, utemp));
		test = binary_expr (GT, utemp, range);
		branch = new_binary_expr ('i', test, high_label);
		append_expr (sw, branch);
		branch = new_binary_expr ('g', table, temp);
		append_expr (sw, branch);
		if (tree->left) {
			append_expr (sw, low_label);
			build_switch (sw, tree->left, op, sw_val, temp, default_label);
		}
		if (tree->right) {
			append_expr (sw, high_label);
			build_switch (sw, tree->right, op, sw_val, temp, default_label);
		}
		for (i = 0; i <= high - low; i++) {
			dstatement_t *st;
			statref_t  *ref;

			st = (dstatement_t *) &pr_globals[G_INT (def->ofs) + i];
			ref = PR_NewStatref (st, 3);
			ref->next = tree->labels[i]->e.label.refs;
			tree->labels[i]->e.label.refs = ref;
		}
	}
}

struct expr_s *
switch_expr (switch_block_t *switch_block, expr_t *break_label,
			 expr_t *statements)
{
	case_label_t **labels, **l;
	case_label_t _default_label;
	case_label_t *default_label = &_default_label;
	expr_t     *sw = new_block_expr ();
	type_t     *type = get_type (switch_block->test);
	expr_t     *sw_val = new_temp_def_expr (type);
	expr_t     *default_expr;
	int         num_labels = 0;
	int         saved_line = pr_source_line;
	string_t    saved_file = s_file;

	pr_source_line = sw_val->line = switch_block->test->line;
	s_file = sw_val->file = switch_block->test->file;

	default_label->value = 0;
	default_label = Hash_DelElement (switch_block->labels, default_label);
	labels = (case_label_t **) Hash_GetList (switch_block->labels);

	if (!default_label) {
		default_label = &_default_label;
		default_label->label = break_label;
	}
	default_expr = new_unary_expr ('g', default_label->label);

	append_expr (sw, new_bind_expr (switch_block->test, sw_val));

	for (l = labels; *l; l++)
		num_labels++;
	if (options.code.progsversion == PROG_ID_VERSION
		|| (type != &type_string
			&& type != &type_float && type != &type_integer)
		|| num_labels < 8) {
		for (l = labels; *l; l++) {
			expr_t     *cmp = binary_expr (EQ, sw_val, (*l)->value);
			expr_t     *test = new_binary_expr ('i',
												test_expr (cmp, 1),
												(*l)->label);

			append_expr (sw, test);
		}
		append_expr (sw, default_expr);
	} else {
		expr_t     *temp;
		int         op;
		case_node_t *case_tree;

		if (type == &type_string)
			temp = new_temp_def_expr (&type_integer);
		else
			temp = new_temp_def_expr (type);
		case_tree = build_case_tree (labels, num_labels, type == &type_integer);
		switch (type->type) {
			case ev_string:
				op = NE;
				break;
			case ev_float:
				op = '-';
				break;
			case ev_integer:
				op = '-';
				break;
			default:
				error (0, "internal compiler error in switch");
				abort ();
		}
		build_switch (sw, case_tree, op, sw_val, temp, default_label->label);
	}
	pr_source_line = saved_line;
	s_file = saved_file;
	append_expr (sw, statements);
	append_expr (sw, break_label);
	return sw;
}