#!/bin/sh

# Regenerate the *-theme.auto.conf files kitty reads at startup from the
# canonical themes in ./theme-modes, honouring the mode recorded in ./theme-mode:
#
#   auto   every appearance keeps its own theme, so kitty follows the OS
#   light  every appearance gets the light theme, so kitty stays light
#   dark   every appearance gets the dark theme, so kitty stays dark
#
# kitty gives the automatic theme files priority over everything else -- includes
# and even --override -- so pinning a mode means writing the wanted theme into
# whichever file the OS makes kitty pick. That is why the real themes live in
# ./theme-modes and these three files are generated. (./themes is separate:
# that is where the themes kitten looks for user themes.)

set -eu

# Permission bits of a file, or 600 if they cannot be read. GNU stat spells this
# `-c %a` while BSD/macOS spells it `-f %Lp`, and each mis-parses the other's
# form -- GNU treats `-f` as --file-system and prints a block of filesystem info
# before failing -- so try one at a time and only accept an octal answer.
file_mode() {
    _m=$(stat -c '%a' "$1" 2>/dev/null) || _m=''
    case "$_m" in
        [0-7][0-7][0-7] | [0-7][0-7][0-7][0-7]) printf '%s\n' "$_m"; return 0 ;;
    esac
    _m=$(stat -f '%Lp' "$1" 2>/dev/null) || _m=''
    case "$_m" in
        [0-7][0-7][0-7] | [0-7][0-7][0-7][0-7]) printf '%s\n' "$_m"; return 0 ;;
    esac
    printf '600\n'
}

script_dir="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)"
config_dir=${1:-"$script_dir"}
canonical_dir="$config_dir/theme-modes"
mode_file="$config_dir/theme-mode"

mode=auto
if [ -f "$mode_file" ]; then
    mode=$(tr -d ' \t\r\n' < "$mode_file")
fi
case "$mode" in
    auto | light | dark) ;;
    *) mode=auto ;;
esac

mkdir -p "$canonical_dir"

# Checksums of the files as this script last wrote them. Anything that differs
# now was rewritten by something else -- in practice the themes kitten saving a
# theme for that appearance -- so it is a new choice and becomes canonical.
# Recording it here rather than in the fish `kitten` wrapper means the choice
# survives however the kitten was launched: `kitty +kitten themes`, a keybinding
# or another shell all bypass that wrapper.
state_file="$config_dir/.theme-generated"

# cksum is POSIX, unlike shasum/sha256sum which differ across platforms.
sum_of() {
    [ -f "$1" ] || return 1
    cksum < "$1"
}

recorded_sum() {
    [ -f "$state_file" ] || return 1
    awk -v want="$1" '$1 == want { $1 = ""; sub(/^ /, ""); print; found = 1 }
                      END { exit !found }' "$state_file"
}

for appearance in dark light no-preference; do
    canonical="$canonical_dir/$appearance.conf"
    generated="$config_dir/$appearance-theme.auto.conf"
    [ -f "$generated" ] || continue

    # First adoption of an existing setup: take whatever is there, but only
    # while following the OS. Under a pinned mode every generated file holds
    # the pinned theme, so adopting them would overwrite the other appearances.
    if [ ! -f "$canonical" ]; then
        [ "$mode" = auto ] && cp "$generated" "$canonical"
        continue
    fi

    # With no state yet we cannot tell a fresh choice from a file we wrote, so
    # leave canonical alone; the checksums recorded below make the next run
    # able to tell.
    now=$(sum_of "$generated") || continue
    was=$(recorded_sum "$appearance") || continue
    [ "$now" = "$was" ] || cp "$generated" "$canonical"
done

for appearance in dark light no-preference; do
    if [ "$mode" = auto ]; then
        source_name=$appearance
    else
        source_name=$mode
    fi

    canonical="$canonical_dir/$source_name.conf"
    [ -f "$canonical" ] || continue

    generated="$config_dir/$appearance-theme.auto.conf"
    mode_bits=600
    if [ -f "$generated" ]; then
        mode_bits=$(file_mode "$generated")
    fi

    tmp=$(mktemp "$generated.tmp.XXXXXX")
    trap 'rm -f "$tmp"' EXIT HUP INT TERM
    cat "$canonical" > "$tmp"
    chmod "$mode_bits" "$tmp"
    mv -f "$tmp" "$generated"
    trap - EXIT HUP INT TERM
done

"$script_dir/repair-auto-themes.sh" "$config_dir"

# Record what we ended up with, after the repair step, so the next run can tell
# an externally-saved theme from one of ours.
tmp_state=$(mktemp "$state_file.tmp.XXXXXX")
trap 'rm -f "$tmp_state"' EXIT HUP INT TERM
for appearance in dark light no-preference; do
    generated="$config_dir/$appearance-theme.auto.conf"
    [ -f "$generated" ] || continue
    printf '%s %s\n' "$appearance" "$(sum_of "$generated")" >> "$tmp_state"
done
chmod 600 "$tmp_state"
mv -f "$tmp_state" "$state_file"
trap - EXIT HUP INT TERM