From d132b86b83cdabfc8076466386b4ff8309f1b940 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Sat, 12 Dec 2020 17:06:31 +0000
Subject: [PATCH] day12: start working

---
 day12/day12.c | 79 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 70 insertions(+), 9 deletions(-)

diff --git a/day12/day12.c b/day12/day12.c
index 98b41e0..800ea09 100644
--- a/day12/day12.c
+++ b/day12/day12.c
@@ -1,5 +1,10 @@
 #include <stdint.h>
+#include <stdlib.h>
 
+#include <panic.h>
+#include <attrs.h>
+
+typedef int64_t i64;
 typedef uint64_t u64;
 
 const char* const input[] = {
@@ -8,22 +13,24 @@ const char* const input[] = {
 #define input_sz (sizeof(input)/sizeof(char*))
 
 typedef struct {
-	u64 x, y;
+	i64 x, y;
 } point_t;
 
 typedef struct {
 	enum direction {
-		DIR_NORTH,
-		DIR_SOUTH,
-		DIR_EAST,
-		DIR_WEST,
+		DIR_INVALID =0,
+
+		DIR_NORTH = 'N',
+		DIR_SOUTH = 'S',
+		DIR_EAST  = 'E',
+		DIR_WEST  = 'W',
 
-		DIR_LEFT,
-		DIR_RIGHT,
+		DIR_LEFT  = 'L',
+		DIR_RIGHT = 'R',
 
-		DIR_FORWARD,
+		DIR_FORWARD='F',
 	} dir;
-	u64 num;
+	i64 num;
 } command_t;
 
 typedef struct ship {
@@ -31,9 +38,63 @@ typedef struct ship {
 	enum direction facing;
 } svec_t;
 
+pure inline static command_t parse_single(const char* from)
+{
+	register command_t o;
+	o.dir = (enum direction)from[0];
+	o.num = (i64)atoll(from+1);
+	return o;
+}
+
+inline static void modsign(struct ship* restrict ship, i64 by)
+{
+	i64* restrict mod;
+	i64 sign = 1;
+	switch(ship->facing)
+	{
+		case DIR_NORTH: sign = -1; fall;
+		case DIR_SOUTH: mod = &ship->pos.y;
+				break;
+
+		case DIR_WEST: sign = -1; fall;
+		case DIR_EAST: mod = &ship->pos.x;
+			       break;
+		default: panic("Invalid facing direction '%c' (%d)", (char) ship->facing, (int) ship->facing);
+	}
+	*mod += sign * by;
+}
+
+static void handle_com(struct ship* restrict ship, command_t com)
+{
+	switch(com.dir)
+	{
+	case DIR_EAST:  ship->pos.x += com.num; break;
+	case DIR_WEST:  ship->pos.x -= com.num; break;
+	case DIR_NORTH: ship->pos.y -= com.num; break;
+	case DIR_SOUTH: ship->pos.y += com.num; break;
+	
+	case DIR_FORWARD: modsign(ship, com.num); break;
+
+	case DIR_LEFT: //TODO:
+	case DIR_RIGHT: //TODO:
+
+	default: panic("Unknown command direction '%c' (%d)", (char)com.dir, (int)com.dir);
+	}
+}
+
+inline extern u64 absll(i64 n)
+{
+	return (u64)(n < 0 ? -n : n);
+}
 
 int main()
 {
+	struct ship ship = { .facing = DIR_EAST, .pos = {0} };
+	//command_t comms[input_sz];
+	for(size_t i=0;i<input_sz;i++)
+		handle_com(&ship, parse_single(input[i]));
+	
+	printf("%lu\n", absll(ship.pos.x) + absll(ship.pos.y));
 	return 0;
 }