#!/usr/bin/env bash

: "${CM_ONESHOT=0}"
: "${CM_OWN_CLIPBOARD=1}"
: "${CM_DEBUG=0}"
: "${CM_DIR="${XDG_RUNTIME_DIR-"${TMPDIR-/tmp}"}"}"
: "${CM_MAX_CLIPS=1000}"

# Shellcheck is mistaken here, this is used later as lowercase.
# shellcheck disable=SC2153
: "${CM_SELECTIONS=clipboard primary}"

major_version=5
cache_dir=$CM_DIR/clipmenu.$major_version.$USER/
cache_file_prefix=$cache_dir/line_cache
lock_file=$cache_dir/lock
lock_timeout=2
has_clipnotify=0

# This comes from the environment, so we rely on word splitting.
# shellcheck disable=SC2206
cm_selections=( $CM_SELECTIONS )

if command -v timeout >/dev/null 2>&1; then
    timeout_cmd=(timeout 1)
else
    echo "WARN: No timeout binary. Continuing without any timeout on xsel." >&2
    timeout_cmd=()
fi

_xsel() {
    "${timeout_cmd[@]}" xsel --logfile /dev/null "$@"
}

get_first_line() {
    # Args:
    # - $1, the file or data
    # - $2, optional, the line length limit

    data=${1?}
    line_length_limit=${2-300}

    # We look for the first line matching regex /./ here because we want the
    # first line that can provide reasonable context to the user. That is, if
    # you have 5 leading lines of whitespace, displaying " (6 lines)" is much
    # less useful than displaying "foo (6 lines)", where "foo" is the first
    # line in the entry with actionable context.
    awk -v limit="$line_length_limit" '
        BEGIN { printed = 0; }

        printed == 0 && NF {
            $0 = substr($0, 0, limit);
            printf("%s", $0);
            printed = 1;
        }

        END {
            if (NR > 1) {
                print " (" NR " lines)";
            } else {
                printf("\n");
            }
        }' <<< "$data"
}

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

element_in() {
    local item element
    item="$1"
    for element in "${@:2}"; do
        if [[ "$item" == "$element" ]]; then
            return 0
        fi
    done
    return 1
}

if [[ $1 == --help ]] || [[ $1 == -h ]]; then
    cat << 'EOF'
clipmenud is the daemon that collects and caches what's on the clipboard.
when you want to select a clip.

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: maximum number of clips to store, 0 for inf (default: 1000)
- $CM_ONESHOT: run once immediately, do not loop (default: 0)
- $CM_OWN_CLIPBOARD: take ownership of the clipboard (default: 1)
- $CM_SELECTIONS: space separated list of the selections to manage (default: "clipboard primary")
EOF
    exit 0
fi


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

declare -A last_data
declare -A last_filename
declare -A last_cache_file_output

command -v clipnotify >/dev/null 2>&1 && has_clipnotify=1

if ! (( has_clipnotify )); then
    echo "WARN: Consider installing clipnotify for better performance." >&2
    echo "WARN: See https://github.com/cdown/clipnotify." >&2
fi

exec {lock_fd}> "$lock_file"

sleep_cmd=(sleep "${CM_SLEEP:-0.5}")

while true; do
    if ! (( CM_ONESHOT )); then
        if (( has_clipnotify )); then
            # Fall back to polling if clipnotify fails
            clipnotify || "${sleep_cmd[@]}"
        else
            # Use old polling method
            "${sleep_cmd[@]}"
        fi
    fi

    if ! flock -x -w "$lock_timeout" "$lock_fd"; then
        if (( CM_ONESHOT )); then
            printf 'ERROR: %s\n' 'Timed out waiting for lock' >&2
            exit 1
        else
            printf 'ERROR: %s\n' \
                'Timed out waiting for lock, skipping this run' >&2
            continue
        fi
    fi

    for selection in "${cm_selections[@]}"; do
        cache_file=${cache_file_prefix}_$selection
        data=$(_xsel -o --"$selection"; printf x)

        debug "Data before stripping: $data"

        # We add and remove the x so that trailing newlines are not stripped.
        # Otherwise, they would be stripped by the very nature of how POSIX
        # defines command substitution.
        data=${data%x}

        debug "Data after stripping: $data"

        if [[ $data != *[^[:space:]]* ]]; then
            debug "Skipping as clipboard is only blank"
            continue
        fi

        if [[ ${last_data[$selection]} == "$data" ]]; then
            debug 'Skipping as last selection is the same as this one'
            continue
        fi


        # If we were in the middle of doing a selection when the previous poll
        # ran, then we may have got a partial clip.
        possible_partial=${last_data[$selection]}
        if [[ $possible_partial && $data == "$possible_partial"* ]] ||
           [[ $possible_partial && $data == *"$possible_partial" ]]; then
            debug "$possible_partial is a possible partial of $data"
            debug "Removing ${last_filename[$selection]}"

            previous_size=$(wc -c <<< "${last_cache_file_output[$selection]}")
            truncate -s -"$previous_size" "$cache_file"

            rm -- "${last_filename[$selection]}"
        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_data[$selection]=$data
        last_filename[$selection]=$filename

        # Recover without restart if we deleted the entire clip dir.
        # It's ok that this only applies to the final directory.
        # shellcheck disable=SC2174
        mkdir -p -m0700 "$cache_dir"

        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"

        last_cache_file_output[$selection]=$cache_file_output

        if (( CM_OWN_CLIPBOARD )) && [[ $selection != primary ]] &&
           element_in clipboard "${cm_selections[@]}"; then
            # Take ownership of the clipboard, in case the original application
            # is unable to serve the clipboard request (due to being suspended,
            # etc).
            #
            # Primary is excluded from the change of ownership as applications
            # sometimes act up if clipboard focus is taken away from them --
            # for example, urxvt will unhilight text, which is undesirable.
            #
            # We can't colocate this with the above copying code because
            # https://github.com/cdown/clipmenu/issues/34 requires knowing if
            # we would skip first.
            _xsel -o --clipboard | _xsel -i --clipboard
        fi

        if (( CM_MAX_CLIPS )) && [[ -f $cache_file ]]; then
            mapfile -t to_remove < <(
                head -n -"$CM_MAX_CLIPS" "$cache_file" |
                    while read -r line; do cksum <<< "${line#* }"; done
            )
            num_to_remove="${#to_remove[@]}"
            if (( num_to_remove )); then
                debug "Removing $num_to_remove old clips"
                rm -- "${to_remove[@]/#/"$cache_dir/"}"
                trunc_tmp=$(mktemp)
                tail -n "$CM_MAX_CLIPS" "$cache_file" | uniq > "$trunc_tmp"
                mv -- "$trunc_tmp" "$cache_file"
            fi
        fi
    done

    flock -u "$lock_fd"

    if (( CM_ONESHOT )); then
        debug 'Oneshot mode enabled, exiting'
        break
    fi
done