solver: fix error detection for certain unsatisfiability cases

did not properly detect as error if name could not be satisfied
due to being available in tagged repository which is not enabled.

src/solver.c

@@ -9,7 +9,6 @@
  * by the Free Software Foundation. See http://www.gnu.org/ for details.
  */
 
-#include <stdlib.h>
 #include "apk_defines.h"
 #include "apk_database.h"
 #include "apk_package.h"
@@ -47,6 +46,7 @@ struct apk_name_state {
 	struct list_head unsolved_list;
 	struct apk_name *name;
 	struct apk_package *chosen;
+	unsigned int topology_last_touched;
 	unsigned int allowed_repos, preferred_repos;
 	unsigned short requirers;
 	unsigned short install_ifs;
@@ -67,8 +67,10 @@ struct apk_solver_state {
 	struct list_head unsolved_list_head;
 	struct apk_package *latest_decision;
 	unsigned int topology_position;
+	unsigned int penalty_topology;
 	unsigned int assigned_names;
 	struct apk_score score;
+	struct apk_score penalty_score;
 
 	unsigned int solver_flags : 4;
 	unsigned int refresh_name_states : 1;
@@ -449,6 +451,7 @@ static void trigger_install_if(struct apk_solver_state *ss,
 
 		dbg_printf("trigger_install_if: " PKG_VER_FMT " triggered\n",
 			   PKG_VER_PRINTF(pkg));
+		ns->topology_last_touched = ss->topology_position;
 		ns->install_ifs++;
 		update_name_state(ss, pkg->name);
 	}
@@ -462,6 +465,7 @@ static void untrigger_install_if(struct apk_solver_state *ss,
 
 		dbg_printf("untrigger_install_if: " PKG_VER_FMT " no longer triggered\n",
 			   PKG_VER_PRINTF(pkg));
+		ns->topology_last_touched = ss->topology_position;
 		ns->install_ifs--;
 		update_name_state(ss, pkg->name);
 	}
@@ -677,6 +681,8 @@ static void apply_constraint(struct apk_solver_state *ss, struct apk_dependency
 
 	if (!dep->optional)
 		ns->requirers++;
+	ns->topology_last_touched = ss->topology_position;
+
 	update_name_state(ss, name);
 }
 
@@ -717,6 +723,8 @@ static void undo_constraint(struct apk_solver_state *ss, struct apk_dependency *
 
 	if (!dep->optional)
 		ns->requirers--;
+	ns->topology_last_touched = ss->topology_position;
+
 	update_name_state(ss, name);
 }
 
@@ -746,6 +754,24 @@ static int expand_branch(struct apk_solver_state *ss)
 	}
 	ss->refresh_name_states = 0;
 	if (pkg0 == NULL) {
+		struct apk_score penalty_score = {0,0};
+		int penalty_topology = 0;
+
+		list_for_each_entry(ns, &ss->unsolved_list_head, unsolved_list) {
+			if (!ns->locked) {
+				penalty_score.unsatisfiable += ns->requirers;
+				penalty_score.preference += ns->name->pkgs->num;
+				if (penalty_topology < ns->topology_last_touched)
+					penalty_topology = ns->topology_last_touched;
+			}
+		}
+		if (ss->penalty_topology < penalty_topology) {
+			ss->penalty_topology = penalty_topology;
+			ss->penalty_score = penalty_score;
+		}
+		ss->score.unsatisfiable += penalty_score.unsatisfiable;
+		ss->score.preference    += penalty_score.preference;
+
 		dbg_printf("expand_branch: list is empty (%d unsatisfied)\n",
 			   ss->score.unsatisfiable);
 		return 1;
@@ -939,6 +965,19 @@ static int cmpscore(struct apk_score *a, struct apk_score *b)
 	return 0;
 }
 
+static int cmpscore2(struct apk_score *a1, struct apk_score *a2, struct apk_score *b)
+{
+	if (a1->unsatisfiable+a2->unsatisfiable < b->unsatisfiable)
+		return -1;
+	if (a1->unsatisfiable+a2->unsatisfiable > b->unsatisfiable)
+		return 1;
+	if (a1->preference+a2->preference < b->preference)
+		return -1;
+	if (a1->preference+a2->preference > b->preference)
+		return 1;
+	return 0;
+}
+
 int apk_solver_solve(struct apk_database *db,
 		     unsigned short solver_flags,
 		     struct apk_dependency_array *world,
@@ -966,7 +1005,12 @@ int apk_solver_solve(struct apk_database *db,
 	zero_score = ss->score;
 
 	do {
-		if (cmpscore(&ss->score, &ss->best_score) < 0) {
+		if (ss->topology_position <= ss->penalty_topology) {
+			ss->penalty_score = zero_score;
+			ss->penalty_topology = 0;
+		}
+
+		if (cmpscore2(&ss->score, &ss->penalty_score, &ss->best_score) < 0) {
 			r = expand_branch(ss);
 			if (r) {
 				dbg_printf("solution with: %d unsatisfiable, %d preference\n",