#!/bin/bash

set -u
set -e

# these wires should give 6
#wire_1=(R8 U5 L5 D3)
#wire_2=(U7 R6 D4 L4)

# these wires should get 159
#wire_1=(R75 D30 R83 U83 L12 D49 R71 U7 L72)
#wire_2=(U62 R66 U55 R34 D71 R55 D58 R83)

# these wires should get 135
#wire_1=(R98 U47 R26 D63 R33 U87 L62 D20 R33 U53 R51)
#wire_2=(U98 R91 D20 R16 D67 R40 U7 R15 U6 R7)

filename=${1:-input.txt}

# read in data from file instead
exec 3<"$filename"
IFS="," read -u 3 -a wire_1
IFS="," read -u 3 -a wire_2

trace_wire() {
    local -n w=$1
    local -n b=$2
    local -n c=$3
    local -n w1cost=$4
    wire_number=$5
    cur_vert=0
    cur_horz=0
    moved=0
    last_replace_char="-"
    cost=0

    for operation in "${w[@]}"; do
        direction=${operation:0:1}
        amount=${operation:1}
        case $direction in
            U)
                operator=+
                ;;
            D)
                operator=-
                ;;
            L)
                operator=-
                ;;
            R)
                operator=+
                ;;
        esac

        case $direction in
            U|D)
                for (( moved=1; moved <= $amount; moved++ )); do
                    cur_vert=$((cur_vert${operator}1))
                    cost=$((cost+1))
                    if [ $wire_number -eq 1 ]; then
                        if ! [ ${w1cost[$cur_horz,$cur_vert]+a} ]; then
                            w1cost[$cur_horz,$cur_vert]=$cost
                        fi
                    fi
                    if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
                        if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
                            cross_wires[$cur_horz,$cur_vert]=$((${w1cost[$cur_horz,$cur_vert]}+$cost))
                            b[$cur_horz,$cur_vert]=3
                        fi
                        continue
                    fi
                    b[$cur_horz,$cur_vert]=$wire_number
                done
                ;;
            L|R)
                for (( moved=1; moved <= $amount; moved++ )); do
                    cur_horz=$((cur_horz${operator}1))
                    cost=$((cost+1))
                    if [ $wire_number -eq 1 ]; then
                        if ! [ ${w1cost[$cur_horz,$cur_vert]+a} ]; then
                            w1cost[$cur_horz,$cur_vert]=$cost
                        fi
                    fi
                    if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
                        if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
                            cross_wires[$cur_horz,$cur_vert]=$((${w1cost[$cur_horz,$cur_vert]}+$cost))
                            b[$cur_horz,$cur_vert]=3
                        fi
                        continue
                    fi
                    b[$cur_horz,$cur_vert]=$wire_number
                done
                ;;
        esac
    done
}

declare -A board
declare -A cross_wires
declare -A wire_1_cost
echo "Tracing first wire"
trace_wire wire_1 board cross_wires wire_1_cost 1
echo "Tracing second wire"
trace_wire wire_2 board cross_wires wire_1_cost 2

echo "Wires cross at:"
min_cost=-1
for cross in "${!cross_wires[@]}"; do
    echo "  $cross ${cross_wires[$cross]}"
    cost=${cross_wires[$cross]}
    if [ $min_cost -lt 0 ] || [ $min_cost -gt $cost ]; then
        min_cost=$cost
    fi
done

echo Min cost: $min_cost