Fix gas handling in planner

Two separate bugs.

a) Air cylinders were created with o2=209 and no other value set.
sanitize_gasmix() turned that into o2=0 which meant that this cylinder was
now identified as "nodata", i.e., unset.
We now set a fake cylinder name to deal with that issue.

b) the gaschange event is inherited from libdivecomputer and therefore
only supports 1 percent granularity for o2 and h2. Since we didn't round
when assigning the value we ended up with air being stored as o2=20 he=0
which of course then didn't match air anymore (which we have defined as
208 <= o2 <= 210).
We now use o2=210 for air in the planner and carefully round the permille
values whenever we convert into percent - and compare gases with percent
granularity as well.

A better fix for b) would be to change the Subsurface event to not simply
copy the libdivecomputer behavior and use percent granularity but support
permille instead. But this closely before the 3.0 release that seemed like
a far too invasive change to make - the changes to the planner should have
no impact outside the planner module.

Reported-by: Chris Lewis <chrislewis915@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

3 files changed, 44 insertions, 18 deletions

diff --git a/dive.c b/dive.c
index 528172a40..e337ca319 100644
--- a/dive.c
+++ b/dive.c
@@ -281,7 +281,7 @@ static void sanitize_gasmix(struct gasmix *mix)
 		if (!o2)
 			return;
 		/* 20.8% to 21% O2 is just air */
-		if (o2 >= (O2_IN_AIR - 1) && o2 <= (O2_IN_AIR + 1)) {
+		if (is_air(o2, he)) {
 			mix->o2.permille = 0;
 			return;
 		}
diff --git a/dive.h b/dive.h
index 84133a424..246521554 100644
--- a/dive.h
+++ b/dive.h
@@ -213,6 +213,11 @@ static inline int mbar_to_PSI(int mbar)
 	return to_PSI(p);
 }
 
+static inline gboolean is_air(int o2, int he)
+{
+	return (he == 0) && (o2 == 0 || ((o2 >= O2_IN_AIR - 1) && (o2 <= O2_IN_AIR + 1)));
+}
+
 /* Linear interpolation between 'a' and 'b', when we are 'part'way into the 'whole' distance from a to b */
 static inline int interpolate(int a, int b, int part, int whole)
 {
diff --git a/planner.c b/planner.c
index 6d7814abf..244fece53 100644
--- a/planner.c
+++ b/planner.c
@@ -12,6 +12,11 @@
 #include "divelist.h"
 #include "display-gtk.h"
 
+/* while we normally track gases with permille precision, in the planner
+ * we want to treat gases as identical based on percent granularity.
+ * The reason for this is that the gaschange event only deals with
+ * percent (this is inherited from libdivecomputer). */
+#define O2_IN_AIR_PERCENT 210
 
 int decostoplevels[] = { 0, 3000, 6000, 9000, 12000, 15000, 18000, 21000, 24000, 27000,
 		     30000, 33000, 36000, 39000, 42000, 45000, 48000, 51000, 54000, 57000,
@@ -57,21 +62,30 @@ void get_gas_from_events(struct divecomputer *dc, int time, int *o2, int *he)
 	}
 }
 
+/* simple helper function to compare two permille values with
+ * (rounded) percent granularity */
+static inline gboolean match_percent(int a, int b)
+{
+	return (a + 5) / 10 == (b + 5) / 10;
+}
 
 static int get_gasidx(struct dive *dive, int o2, int he)
 {
 	int gasidx = -1;
 
+	/* we treat air as 0/0 because it is special */
+	if (is_air(o2, he))
+		o2 = 0;
 	while (++gasidx < MAX_CYLINDERS)
-		if (dive->cylinder[gasidx].gasmix.o2.permille == o2 &&
-		    dive->cylinder[gasidx].gasmix.he.permille == he)
+		if (match_percent(dive->cylinder[gasidx].gasmix.o2.permille, o2) &&
+		    match_percent(dive->cylinder[gasidx].gasmix.he.permille, he))
 			return gasidx;
 	return -1;
 }
 
 static void get_gas_string(int o2, int he, char *text, int len)
 {
-	if (he == 0 && (o2 == 0 || (o2 >= O2_IN_AIR - 1 && o2 <= O2_IN_AIR + 1)))
+	if (is_air(o2, he))
 		snprintf(text, len, _("air"));
 	else if (he == 0)
 		snprintf(text, len, _("EAN%d"), (o2 + 5) / 10);
@@ -105,7 +119,7 @@ double tissue_at_end(struct dive *dive, char **cached_datap)
 		t1 = sample->time.seconds;
 		get_gas_from_events(&dive->dc, t0, &o2, &he);
 		if ((gasidx = get_gasidx(dive, o2, he)) == -1) {
-			printf("can't find gas %d/%d\n", o2/10, he/10);
+			printf("can't find gas %d/%d\n", (o2 + 5) / 10, (he + 5) / 10);
 			gasidx = 0;
 		}
 		if (i > 0)
@@ -153,19 +167,21 @@ int add_gas(struct dive *dive, int o2, int he)
 
 	for (i = 0; i < MAX_CYLINDERS; i++) {
 		cyl = dive->cylinder + i;
+		mix = &cyl->gasmix;
 		if (cylinder_nodata(cyl))
 			break;
-		mix = &cyl->gasmix;
-		if (o2 == mix->o2.permille && he == mix->he.permille)
+		if (match_percent(o2, mix->o2.permille) && match_percent(he, mix->he.permille))
 			return i;
 	}
 	if (i == MAX_CYLINDERS) {
 		printf("too many cylinders\n");
 		return -1;
 	}
-	mix = &cyl->gasmix;
 	mix->o2.permille = o2;
 	mix->he.permille = he;
+	/* since air is stored as 0/0 we need to set a name or an air cylinder
+	 * would be seen as unset (by cylinder_nodata()) */
+	cyl->type.description = strdup("Cylinder for planning");
 	return i;
 }
 
@@ -175,7 +191,7 @@ struct dive *create_dive_from_plan(struct diveplan *diveplan)
 	struct divedatapoint *dp;
 	struct divecomputer *dc;
 	struct sample *sample;
-	int oldo2 = O2_IN_AIR, oldhe = 0;
+	int oldo2 = O2_IN_AIR_PERCENT, oldhe = 0;
 	int oldpo2 = 0;
 	int lasttime = 0;
 
@@ -226,14 +242,18 @@ struct dive *create_dive_from_plan(struct diveplan *diveplan)
 			oldpo2 = po2;
 		}
 
-		/* Create new gas, and gas change event if necessary */
+		/* Create new gas, and gas change event if necessary;
+		 * Sadly, we inherited our gaschange event from libdivecomputer which only
+		 * support percentage values, so round the entries */
 		if (o2 != oldo2 || he != oldhe) {
-			int value = (o2 / 10) | (he / 10 << 16);
-			add_gas(dive, o2, he);
+			int plano2 = (o2 + 5) / 10 * 10;
+			int planhe = (he + 5) / 10 * 10;
+			int value;
+			add_gas(dive, plano2, planhe);
+			value = (plano2 / 10) | (planhe << 16);
 			add_event(dc, lasttime, 25, 0, value, "gaschange"); // SAMPLE_EVENT_GASCHANGE2
 			oldo2 = o2; oldhe = he;
 		}
-
 		/* Create sample */
 		sample = prepare_sample(dc);
 		/* set po2 at beginning of this segment */
@@ -395,8 +415,8 @@ static struct gaschanges *analyze_gaslist(struct diveplan *diveplan, struct dive
 #if DEBUG_PLAN & 16
 	for (nr = 0; nr < *gaschangenr; nr++)
 		printf("gaschange nr %d: @ %5.2lfm gasidx %d (%d/%d)\n", nr, gaschanges[nr].depth / 1000.0,
-			gaschanges[nr].gasidx, dive->cylinder[gaschanges[nr].gasidx].gasmix.o2.permille / 10,
-			dive->cylinder[gaschanges[nr].gasidx].gasmix.he.permille / 10);
+			gaschanges[nr].gasidx, (dive->cylinder[gaschanges[nr].gasidx].gasmix.o2.permille + 5) / 10,
+			(dive->cylinder[gaschanges[nr].gasidx].gasmix.he.permille + 5) / 10);
 #endif
 	return gaschanges;
 }
@@ -521,7 +541,8 @@ static void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive)
 							FRACTION(dp->time, 60),
 							gas);
 		}
-		consumption[gasidx] += used;
+		if (gasidx != -1)
+			consumption[gasidx] += used;
 		get_gas_string(newo2, newhe, gas, sizeof(gas));
 		if (o2 != newo2 || he != newhe) {
 			len = strlen(buffer);
@@ -619,7 +640,7 @@ void plan(struct diveplan *diveplan, char **cached_datap, struct dive **divep)
 			he = dive->cylinder[gaschanges[gi].gasidx].gasmix.he.permille;
 #if DEBUG_PLAN & 16
 			printf("switch to gas %d (%d/%d) @ %5.2lfm\n", gaschanges[gi].gasidx,
-				o2 / 10, he / 10, gaschanges[gi].depth / 1000.0);
+				(o2 + 5) / 10, (he + 5) / 10, gaschanges[gi].depth / 1000.0);
 #endif
 			gi--;
 		}
@@ -730,7 +751,7 @@ static int validate_gas(const char *text, int *o2_p, int *he_p)
 		return 0;
 
 	if (!strcasecmp(text, _("air"))) {
-		o2 = O2_IN_AIR; he = 0; text += strlen(_("air"));
+		o2 = O2_IN_AIR_PERCENT; he = 0; text += strlen(_("air"));
 	} else if (!strncasecmp(text, _("ean"), 3)) {
 		o2 = get_permille(text+3, &text); he = 0;
 	} else {