1 files changed, 85 insertions, 0 deletions
diff --git a/src/day10.rs b/src/day10.rs
new file mode 100644
index 0000000..9e63802
--- /dev/null
+++ b/src/day10.rs
@@ -0,0 +1,85 @@
+use std::ops::Add;
+
+fn cycles(op: &str) -> usize {
+    match op {
+        "noop" => 1,
+        "addx" => 2,
+        unk => panic!("unknown op {}", unk)
+    }
+}
+
+fn op_and_args(instruction: &str) -> (&str, Option<i32>) {
+    let mut toks = instruction.split_whitespace();
+    let op = toks.next().expect("expected an operator!");
+    let arg = match op {
+        "noop" => None,
+        "addx" => {
+            let arg1: i32 = toks.next().expect("expected one arg for addx").parse().expect("arg for addx must be i32");
+            Some(arg1)
+        },
+        unk => panic!("unknown op {}", unk)
+    };
+    (op,arg)
+}
+
+fn apply(op: &str, arg: Option<i32>, x: i32) -> i32 {
+    match op {
+        "noop" => x,
+        "addx" => x + arg.expect("addx had no argument!"),
+        unk => panic!("unknown op {}", unk) 
+    }
+}
+
+pub fn run(input: String) {
+    let mut lines = input.lines().into_iter();
+    // our (single) register
+    let mut x = 1;
+    let mut tick = 1;
+    let first_instruction: &str = lines.next().expect("expected a first instruction!");
+    let (mut op, mut arg) = op_and_args(first_instruction);
+    let mut circ = cycles(op);
+    //let mut sss = 0;
+    let mut screen = "".to_owned();
+    loop {
+        // Start of cycle, Load next instruction
+        if circ == 0 {
+            if let Some(next_inst) = lines.next() {
+                (op, arg)= op_and_args(next_inst);
+                circ = cycles(op);    
+            } else {
+                break;
+            }
+        }
+        // Time passes....
+        circ -= 1;
+
+        // Pt1, signal strength
+        // if (tick + 20) % 40 == 0 {
+        //     let ss = tick*x;
+        //     //println!("tick {} x {} ss {}", tick, x, ss);
+        //     sss += ss;
+        // }
+
+        // Pt2, Draw pixels! note crt_col is one less(!) than tick
+        let crt_col = (tick-1) % 40;
+        //println!("tick {} x {} crt_col {}", tick, x, crt_col);
+        screen = screen.add(if crt_col >= (x-1) && crt_col <= (x+1) {
+            "#"
+        } else {
+            "."
+        });
+        if crt_col == 39 {
+            screen = screen.add("\n");
+        }
+
+        // End of cycle, apply instruction
+        if circ == 0 {
+            x = apply(op, arg, x);
+        }
+        // increase cycle counter
+        tick += 1;
+    }
+    //println!("Day 10: {}",sss);
+    println!("Day 10:");
+    print!("{}", screen);
+}
+\ No newline at end of file