#!/usr/bin/env bash
#
# mangohud-logger — toggle MangoHud CSV logging on/off
#
# Just run it: if logging is off it gets switched on, if it's already on
# it gets switched off.
#
# What it manages on enable:
#   1. ~/.config/MangoHud/MangoHud.conf
#      → appends a marker block with output_folder, autostart_log, etc.
#      → keeps your existing keys; overrides `no_display` while logging
#        (autostart_log rides on the render hook that no_display disables).
#   2. ~/.config/environment.d/95-mangohud-logger.conf
#      → contains MANGOHUD=1 so the Vulkan layer auto-loads into every
#        game (gamescope sessions, Steam, native Vulkan apps).
#        Picked up by systemd-user at next session login.
#
# Logs land in the user's Downloads folder under "mango-logs"
# (honours XDG_DOWNLOAD_DIR from ~/.config/user-dirs.dirs, else ~/Downloads).

set -euo pipefail

readonly MARKER_BEGIN="# >>> mangohud-logger BEGIN >>>"
readonly MARKER_END="# <<< mangohud-logger END <<<"

CONFIG_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/MangoHud"
CONFIG_FILE="$CONFIG_DIR/MangoHud.conf"

ENV_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/environment.d"
ENV_FILE="$ENV_DIR/95-mangohud-logger.conf"

GS_SESSION_DIR="${XDG_CONFIG_HOME:-$HOME/.config}/gamescope-session-plus/sessions.d"
GS_SESSION_FILE="$GS_SESSION_DIR/steam"
GS_OWNED_MARKER="# Written by mangohud-logger."

# Detect which gamescope (Game Mode) session manager is in use — this decides
# whether our env override is actually sourced at session start:
#   plus    → gamescope-session-plus sources ~/.config/gamescope-session-plus/
#             sessions.d/* after its own steam script, so our override works.
#   steamos → /usr/lib/steamos/gamescope-session hard-exports
#             STEAM_USE_MANGOAPP=1 and MANGOHUD_CONFIGFILE=<tmp>/no_display, and
#             sources NO user file. A global override is therefore impossible;
#             logging requires per-game Steam launch options instead.
#   none    → no gamescope session found (desktop-only machine).
detect_gs_flavor() {
  if [[ -e /usr/share/gamescope-session-plus/sessions.d/steam ]]; then
    printf 'plus\n'
  elif [[ -e /usr/lib/steamos/gamescope-session ]]; then
    printf 'steamos\n'
  else
    printf 'none\n'
  fi
}
GS_FLAVOR="$(detect_gs_flavor)"

# The per-game launch-option string that makes logging work on the steamos
# flavor (repoints MANGOHUD_CONFIGFILE back at our config so autostart_log fires).
LAUNCH_OPT="MANGOHUD_CONFIGFILE=$CONFIG_FILE mangohud %command%"

# Resolve Downloads via xdg-user-dir if available, else the user-dirs.dirs file,
# else fall back to ~/Downloads. This makes the script work on non-English locales.
if command -v xdg-user-dir >/dev/null 2>&1; then
  DOWNLOADS_DIR="$(xdg-user-dir DOWNLOAD)"
elif [[ -f "${XDG_CONFIG_HOME:-$HOME/.config}/user-dirs.dirs" ]]; then
  # shellcheck disable=SC1090,SC1091
  source "${XDG_CONFIG_HOME:-$HOME/.config}/user-dirs.dirs"
  DOWNLOADS_DIR="${XDG_DOWNLOAD_DIR:-$HOME/Downloads}"
else
  DOWNLOADS_DIR="$HOME/Downloads"
fi
LOG_DIR="$DOWNLOADS_DIR/mango-logs"

err()  { printf '\033[31merror:\033[0m %s\n' "$*" >&2; }
info() { printf '\033[36m::\033[0m %s\n' "$*"; }
ok()   { printf '\033[32m✓\033[0m %s\n' "$*"; }
warn() { printf '\033[33m!\033[0m %s\n' "$*"; }

if ! command -v mangohud >/dev/null 2>&1; then
  err "mangohud is not installed — install it first (e.g. 'sudo pacman -S mangohud lib32-mangohud')."
  exit 1
fi

mkdir -p "$CONFIG_DIR"
[[ -f "$CONFIG_FILE" ]] || : > "$CONFIG_FILE"

if grep -qF "$MARKER_BEGIN" "$CONFIG_FILE"; then
  # Currently enabled → strip the block and remove the env file.
  tmp=$(mktemp)
  awk -v b="$MARKER_BEGIN" -v e="$MARKER_END" '
    $0 == b { skip = 1; next }
    $0 == e { skip = 0; next }
    !skip   { print }
  ' "$CONFIG_FILE" > "$tmp"
  # Trim trailing blank lines the block may have left behind.
  sed -i -e :a -e '/^\s*$/{$d;N;ba' -e '}' "$tmp"
  mv "$tmp" "$CONFIG_FILE"

  env_removed=0
  if [[ -f "$ENV_FILE" ]]; then
    rm -f "$ENV_FILE"
    env_removed=1
  fi

  # Only remove the gamescope session override if WE wrote it.
  gs_removed=0
  if [[ -f "$GS_SESSION_FILE" ]] && head -1 "$GS_SESSION_FILE" | grep -qF "$GS_OWNED_MARKER"; then
    rm -f "$GS_SESSION_FILE"
    gs_removed=1
  fi

  ok "MangoHud logging disabled"
  info "existing logs kept in: $LOG_DIR"
  if (( env_removed )); then
    info "removed: $ENV_FILE"
    info "MANGOHUD env var stays set in the *current* session until logout"
  fi
  if (( gs_removed )); then
    info "removed: $GS_SESSION_FILE"
  fi
else
  # Currently disabled → append the config block + write the env file.
  # Check for pre-existing manual log keys *before* we write, so the warning is accurate.
  manual_log_keys=0
  if grep -qE '^\s*(output_folder|autostart_log|log_duration|log_interval|toggle_logging)\s*=' "$CONFIG_FILE"; then
    manual_log_keys=1
  fi

  mkdir -p "$LOG_DIR"
  {
    [[ -s "$CONFIG_FILE" ]] && printf '\n'
    printf '%s\n' "$MARKER_BEGIN"
    printf '# Added by mangohud-logger — remove this block to disable logging.\n'
    printf 'output_folder=%s\n' "$LOG_DIR"
    printf 'autostart_log=1\n'
    printf 'log_duration=0\n'
    printf 'log_interval=100\n'
    printf 'toggle_logging=Shift_L+F2\n'
    # Override any earlier `no_display` — MangoHud's autostart_log rides on the
    # render hook, which `no_display` disables. Without this, logs never start.
    printf 'no_display=0\n'
    printf '%s\n' "$MARKER_END"
  } >> "$CONFIG_FILE"

  # Inline config string mirroring the MangoHud.conf block. MANGOHUD_CONFIG takes
  # precedence over MANGOHUD_CONFIGFILE, so this is what makes logging work GLOBALLY
  # in SteamOS Game Mode — that session forces MANGOHUD_CONFIGFILE=<tmp>/no_display,
  # but it never sets MANGOHUD_CONFIG, so ours (from environment.d) wins for every game.
  # NOTE: relies on output_folder having no commas/spaces (true for the default path).
  MH_INLINE="output_folder=$LOG_DIR,autostart_log=1,log_duration=0,log_interval=100,toggle_logging=Shift_L+F2,no_display=0"

  mkdir -p "$ENV_DIR"
  cat > "$ENV_FILE" <<EOF
$GS_OWNED_MARKER Delete this file (or re-run the script) to remove.
# MANGOHUD=1 makes the Vulkan loader inject the MangoHud layer into every game.
MANGOHUD=1
# MANGOHUD_CONFIG (inline) OVERRIDES MANGOHUD_CONFIGFILE. SteamOS Game Mode forces
# MANGOHUD_CONFIGFILE=<tmp>/no_display, which would otherwise suppress our config and
# stop logging. This inline config wins over it, so autostart_log/output_folder take
# effect for every game with NO per-game launch options. Verified: MANGOHUD_CONFIG
# beats a no_display configfile (vkcube CSV log produced).
MANGOHUD_CONFIG=$MH_INLINE
EOF

  # Game Mode handling depends on which session manager is installed (see
  # detect_gs_flavor). Only gamescope-session-plus sources our override file;
  # the steamos flavor needs per-game launch options instead.
  gs_action=""
  if [[ "$GS_FLAVOR" == "plus" ]]; then
    # gamescope-session-plus override — only write if file is absent or already
    # ours, so we never trample a user-written override.
    if [[ ! -f "$GS_SESSION_FILE" ]] || head -1 "$GS_SESSION_FILE" | grep -qF "$GS_OWNED_MARKER"; then
      mkdir -p "$GS_SESSION_DIR"
      cat > "$GS_SESSION_FILE" <<EOF
$GS_OWNED_MARKER
# Sourced AFTER /usr/share/gamescope-session-plus/sessions.d/steam (last wins).
#
# Without this:
#   1. The system steam session script exports MANGOHUD_CONFIGFILE pointing to a
#      temp file containing only "no_display", which suppresses our user
#      ~/.config/MangoHud/MangoHud.conf and so autostart_log/output_folder
#      never take effect. Unsetting the var falls back to the user file.
#   2. STEAM_USE_MANGOAPP=1 makes Steam ask gamescope to use the mangoapp
#      compositor overlay instead of the in-game MangoHud Vulkan layer.
#      The Vulkan layer is the one that writes CSV logs.

unset MANGOHUD_CONFIGFILE
export STEAM_USE_MANGOAPP=0
export STEAM_MANGOAPP_PRESETS_SUPPORTED=0
EOF
      gs_action="written"
    else
      gs_action="left alone (you have a custom override at $GS_SESSION_FILE)"
    fi
  elif [[ "$GS_FLAVOR" == "steamos" ]]; then
    # This build uses /usr/lib/steamos/gamescope-session, which hard-exports
    # MANGOHUD_CONFIGFILE=<tmp>/no_display and STEAM_USE_MANGOAPP=1 with no user
    # hook — so a global override is impossible. Remove any stale override we
    # wrote on a previous (plus-flavor) run so it doesn't mislead.
    if [[ -f "$GS_SESSION_FILE" ]] && head -1 "$GS_SESSION_FILE" | grep -qF "$GS_OWNED_MARKER"; then
      rm -f "$GS_SESSION_FILE"
    fi
    gs_action="n/a — using MANGOHUD_CONFIG (global, no override file needed)"
  else
    gs_action="no gamescope session detected (desktop only)"
  fi

  if (( manual_log_keys )); then
    warn "pre-existing log-related keys found in config — they may override ours."
  fi

  ok "MangoHud logging enabled"
  info "log folder:   $LOG_DIR"
  info "toggle key:   Shift+F2 (during a game)"
  info "config file:  $CONFIG_FILE"
  info "env file:     $ENV_FILE  (MANGOHUD=1)"
  info "session type: $GS_FLAVOR  (gamescope override: $gs_action)"
  info "note: while logging is on, the HUD becomes visible during games"
  info "      (autostart_log needs the render hook that no_display disables)"

  if [[ "$GS_FLAVOR" == "steamos" ]]; then
    # SteamOS Game Mode forces MANGOHUD_CONFIGFILE=<tmp>/no_display, but our
    # MANGOHUD_CONFIG (set above in environment.d) overrides it for every game —
    # so logging IS global here, no per-game launch options needed.
    info "→ logging is GLOBAL via MANGOHUD_CONFIG — no per-game launch options needed."
    warn "log out and back into Game Mode (or reboot) so environment.d takes effect."
    info "while logging, the in-game MangoHud overlay will be visible (autostart_log"
    info "needs the render hook that no_display disables) — that's expected."
    info "fallback for a single game (e.g. if you don't want to restart the session):"
    printf '    \033[1m%s\033[0m\n' "$LAUNCH_OPT"
  else
    warn "log out and back in (or restart your gamescope session) so the env var takes effect."
  fi
fi