#!/usr/bin/env bash

: "${CM_ONESHOT=0}"
: "${CM_OWN_CLIPBOARD=0}"
: "${CM_SYNC_PRIMARY_TO_CLIPBOARD=0}"
: "${CM_DEBUG=0}"

: "${CM_MAX_CLIPS:=1000}"
# Buffer to batch to avoid calling too much. Only used if CM_MAX_CLIPS >0.
CM_MAX_CLIPS_THRESH=$(( CM_MAX_CLIPS + 10 ))

: "${CM_SELECTIONS:=clipboard primary}"
read -r -a selections <<< "$CM_SELECTIONS"

cache_dir=$(clipctl cache-dir)
cache_file=$cache_dir/line_cache
status_file=$cache_dir/status

# lock_file: lock for *one* iteration of clipboard capture/propagation
# session_lock_file: lock to prevent multiple clipmenud daemons
lock_file=$cache_dir/lock
session_lock_file=$cache_dir/session_lock
lock_timeout=2
has_xdotool=0

_xsel() { timeout 1 xsel --logfile /dev/null "$@"; }

error() { printf 'ERROR: %s\n' "${1?}" >&2; }
info() { printf 'INFO: %s\n' "${1?}"; }
die() {
    error "${2?}"
    exit "${1?}"
}

make_line_cksums() { while read -r line; do cksum <<< "${line#* }"; done; }

get_first_line() {
    data=${1?}

    # We look for the first line matching regex /./ here because we want the
    # first line that can provide reasonable context to the user.
    awk -v limit=300 '
        BEGIN { printed = 0; }
        printed == 0 && NF {
            $0 = substr($0, 0, limit);
            printf("%s", $0);
            printed = 1;
        }
        END {
            if (NR > 1)
                printf(" (%d lines)", NR);
            printf("\n");
        }' <<< "$data"
}

debug() { (( CM_DEBUG )) && printf '%s\n' "$@" >&2; }

sig_disable() {
    info "Received disable signal, suspending clipboard capture"
    _CM_DISABLED=1
    echo "disabled" > "$status_file"
}

sig_enable() {
    if ! (( _CM_DISABLED )); then
        info "Received enable signal but we're not disabled, so doing nothing"
        return
    fi

    # Still store the last data so we don't end up eventually putting it in the
    # clipboard if it wasn't changed
    for selection in "${selections[@]}"; do
        data=$(_xsel -o --"$selection"; printf x)
        last_data_sel[$selection]=${data%x}
    done

    info "Received enable signal, resuming clipboard capture"
    _CM_DISABLED=0
    echo "enabled" > "$status_file"
}

kill_background_jobs() {
    # While we usually _are_, there are no guarantees that we're the process
    # group leader. As such, all we can do is look at the pending jobs. Bash
    # avoids a subshell here, so the job list is in the right shell.
    local bg
    bg=$(jobs -p)

    # Don't log `kill' failures, since with KillMode=control-group, we're
    # racing with init.
    [[ $bg ]] && kill -- "$bg" 2>/dev/null
}

if [[ $1 == --help ]] || [[ $1 == -h ]]; then
    cat << 'EOF'
clipmenud collects and caches what's on the clipboard. You can manage its
operation with clipctl.

Environment variables:

- $CM_DEBUG: turn on debugging output (default: 0)
- $CM_DIR: specify the base directory to store the cache dir in (default: $XDG_RUNTIME_DIR, $TMPDIR, or /tmp)
- $CM_MAX_CLIPS: soft maximum number of clips to store, 0 for inf. At $CM_MAX_CLIPS + 10, the number of clips is reduced to $CM_MAX_CLIPS (default: 1000)
- $CM_ONESHOT: run once immediately, do not loop (default: 0)
- $CM_OWN_CLIPBOARD: take ownership of the clipboard. Note: this may cause missed copies if some other application also handles the clipboard directly (default: 0)
- $CM_SELECTIONS: space separated list of the selections to manage (default: "clipboard primary")
- $CM_SYNC_PRIMARY_TO_CLIPBOARD: sync selections from primary to clipboard immediately (default: 0)
- $CM_IGNORE_WINDOW: disable recording the clipboard in windows where the windowname matches the given regex (e.g. a password manager), do not ignore any windows if unset or empty (default: unset)
EOF
    exit 0
fi

[[ $DISPLAY ]] || die 2 'The X display is unset, is your X server running?'

# It's ok that this only applies to the final directory.
# shellcheck disable=SC2174
mkdir -p -m0700 "$cache_dir"
echo "enabled" > "$status_file"

exec {session_lock_fd}> "$session_lock_file"
flock -x -n "$session_lock_fd" ||
    die 2 "Can't lock session file -- is another clipmenud running?"

declare -A last_data_sel
declare -A updated_sel

command -v clipnotify >/dev/null 2>&1 || die 2 "clipnotify not in PATH"
command -v xdotool >/dev/null 2>&1 && has_xdotool=1

if [[ $CM_IGNORE_WINDOW ]] && ! (( has_xdotool )); then
    echo "WARN: CM_IGNORE_WINDOW does not work without xdotool, which is not installed" >&2
fi

exec {lock_fd}> "$lock_file"

trap '_CM_TRAP=1; sig_disable' USR1
trap '_CM_TRAP=1; sig_enable' USR2
trap 'trap - INT TERM EXIT; kill_background_jobs; exit 0' INT TERM EXIT

while true; do
    if ! (( CM_ONESHOT )); then
        # Make sure we're interruptible for the sig_{en,dis}able traps
        clipnotify &
        _CM_CLIPNOTIFY_PID="$!"
        wait "$_CM_CLIPNOTIFY_PID"
    fi

    # Trapping a signal breaks the `wait`
    if (( _CM_TRAP )); then
        # Prevent spawning another clipnotify job restarting the loop
        kill_background_jobs
        unset _CM_TRAP
        continue
    fi

    if (( _CM_DISABLED )); then
        info "Got a clipboard notification, but we are disabled, skipping"
        continue
    fi

    if [[ $CM_IGNORE_WINDOW ]] && (( has_xdotool )); then
        windowname="$(xdotool getactivewindow getwindowname)"
        if [[ "$windowname" =~ $CM_IGNORE_WINDOW ]]; then
            debug "ignoring clipboard because windowname \"$windowname\" matches \"${CM_IGNORE_WINDOW}\""
            continue
        fi
    fi

    if ! flock -x -w "$lock_timeout" "$lock_fd"; then
        if (( CM_ONESHOT )); then
            die 1 "Timed out waiting for lock"
        else
            error "Timed out waiting for lock, skipping this iteration"
            continue
        fi
    fi

    for selection in "${selections[@]}"; do
        updated_sel[$selection]=0

        data=$(_xsel -o --"$selection"; printf x)
        data=${data%x}  # avoid trailing newlines being stripped

        [[ $data == *[^[:space:]]* ]] || continue
        [[ $last_data == "$data" ]] && continue
        [[ ${last_data_sel[$selection]} == "$data" ]] && continue

        if [[ $last_data && $data == "$last_data"* ]] ||
           [[ $last_data && $data == *"$last_data" ]]; then
            # Don't actually remove the file yet, because it might be
            # referenced by an older entry. These will be dealt with at vacuum.
            debug "$selection: $last_data is a possible partial of $data"
            previous_size=$(wc -c <<< "$last_cache_file_output")
            truncate -s -"$previous_size" "$cache_file"
        fi

        first_line=$(get_first_line "$data")
        debug "New clipboard entry on $selection selection: \"$first_line\""

        cache_file_output="$(date +%s%N) $first_line"
        filename="$cache_dir/$(cksum <<< "$first_line")"
        last_cache_file_output=$cache_file_output
        last_data=$data
        last_data_sel[$selection]=$data
        updated_sel[$selection]=1

        debug "Writing $data to $filename"
        printf '%s' "$data" > "$filename"
        debug "Writing $cache_file_output to $cache_file"
        printf '%s\n' "$cache_file_output" >> "$cache_file"

        if (( CM_OWN_CLIPBOARD )) && [[ $selection == clipboard ]]; then
            # Only clipboard, since apps like urxvt will unhilight for PRIMARY
            _xsel -o --clipboard | _xsel -i --clipboard
        fi
    done

    if (( CM_SYNC_PRIMARY_TO_CLIPBOARD )) && (( updated_sel[primary] )); then
        _xsel -o --primary | _xsel -i --clipboard
    fi

    # The cache file may not exist if this is the first run and data is skipped
    if (( CM_MAX_CLIPS )) && [[ -f "$cache_file" ]] && (( "$(wc -l < "$cache_file")" > CM_MAX_CLIPS_THRESH )); then
        info "Trimming clip cache to CM_MAX_CLIPS ($CM_MAX_CLIPS)"
        trunc_tmp=$(mktemp)
        tail -n "$CM_MAX_CLIPS" "$cache_file" | uniq > "$trunc_tmp"
        mv -- "$trunc_tmp" "$cache_file"

        # Vacuum up unreferenced clips. They may either have been
        # unreferenced by the above CM_MAX_CLIPS code, or they may be old
        # possible partials.
        declare -A cksums
        while IFS= read -r line; do
            cksum=$(cksum <<< "$line")
            cksums["$cksum"]="$line"
        done < <(cut -d' ' -f2- < "$cache_file")

        num_vacuumed=0
        for file in "$cache_dir"/[012346789]*; do
            cksum=${file##*/}
            if [[ ${cksums["$cksum"]-_missing_} == _missing_ ]]; then
                debug "Vacuuming due to lack of reference: $file"
                (( ++num_vacuumed ))
                rm -- "$file"
            fi
        done
        unset cksums
        info "Vacuumed $num_vacuumed clip files."
    fi

    flock -u "$lock_fd"

    (( CM_ONESHOT )) && break
done