#!/bin/bash

CONFIG_DIR="${HOME}/.config/set-screen"

function get_display_state_hash() {
    local hash etc
    read hash etc < <(
    for i in /sys/class/drm/card*/card*-*; do
        echo $i
        cat $i/status
        cat $i/edid
    done | sha1sum -b)
    echo "$hash"
}

function display_state_dir() {
    local hash
    hash="$(get_display_state_hash)"
    echo "${CONFIG_DIR}/$hash"
}

function make_display_state_dir() {
    local dir
    dir="$(display_state_dir)"
    mkdir -p "$dir"
    echo "Created $dir"
    if [[ -n "$1" ]]; then
        local srccmd="${CONFIG_DIR}/$1/command"
        if [[ -x "$srccmd" ]]; then
            ln -s "$srccmd" "$dir/command" && \
                echo "Linked <$1> command"
        else
            echo "<$1> command is not there, ignoring"
        fi
    fi
}

function run_display_state_commands() {
    local dir
    dir="$(display_state_dir)"

    if [[ -x "${dir}/command" ]]; then
        if [[ -x "${CONFIG_DIR}/pre-command" ]]; then
            "${CONFIG_DIR}/pre-command"
        fi
        "${dir}/command"
        if [[ -x "${CONFIG_DIR}/post-command" ]]; then
            "${CONFIG_DIR}/post-command"
        fi
    else
        >&2 echo "There's no settings for the current display configuration; run '$0 make' to create them"
    fi
}

function print_usage() {
    cat <<EOF
$0 -- re-configure screens

Usage:
 $0 make   create directory for current state
 $0 which  show directory for current state
 $0 set    execute 'command' script in directory for current state
 $0        same as 'set'
 $0 help   show this text
EOF
}

case "$1" in
    'make') make_display_state_dir "$2" ;;
    'which') display_state_dir ;;
    '' | 'set') run_display_state_commands ;;
    'help' | '--help' ) print_usage ; exit 0 ;;
    *) >&2 print_usage; exit 1 ;;
esac