#!/bin/sh
set -eu

# Spork installer for Linux, macOS, and WSL.
# Published at https://spork.sh/install

umask 022

fail() {
    printf '%s\n' "Error: $*" >&2
    exit 1
}

# Keep every destructive path anchored below a normal absolute home directory.
if [ -z "${HOME:-}" ]; then
    fail "HOME is not set."
fi
case "$HOME" in
    /*) ;;
    *) fail "HOME must be an absolute path." ;;
esac
if [ ! -d "$HOME" ]; then
    fail "HOME does not name an existing directory."
fi
if ! HOME_DIR=$(CDPATH= cd -P "$HOME" 2>/dev/null && pwd -P); then
    fail "could not resolve HOME."
fi
if [ "$HOME_DIR" = "/" ]; then
    fail "refusing to install with HOME resolving to /."
fi

SPORK_HOME="$HOME_DIR/.spork"
BIN_DIR="$HOME_DIR/.local/bin"
VENV_DIR="$SPORK_HOME/venv"
LAUNCHER="$BIN_DIR/spork"
BACKUP_DIR="$SPORK_HOME/venv.backup.$$"
TEMP_LAUNCHER="$BIN_DIR/.spork-launcher.$$"
PYPI_URL="https://pypi.org/simple"

# Refuse surprising filesystem layouts rather than deleting through them.
if [ -L "$SPORK_HOME" ]; then
    fail "$SPORK_HOME is a symbolic link; refusing to modify it."
fi
if [ -e "$SPORK_HOME" ] && [ ! -d "$SPORK_HOME" ]; then
    fail "$SPORK_HOME exists and is not a directory."
fi
if [ -L "$VENV_DIR" ]; then
    fail "$VENV_DIR is a symbolic link; refusing to remove it."
fi
if [ -e "$VENV_DIR" ] && [ ! -d "$VENV_DIR" ]; then
    fail "$VENV_DIR exists and is not a managed environment."
fi
if [ -e "$BIN_DIR" ] && [ ! -d "$BIN_DIR" ]; then
    fail "$BIN_DIR exists and is not a directory."
fi
if [ -e "$LAUNCHER" ] && [ ! -L "$LAUNCHER" ]; then
    fail "$LAUNCHER exists and is not a symbolic link; refusing to replace it."
fi
if [ -L "$LAUNCHER" ] && [ -d "$LAUNCHER" ]; then
    fail "$LAUNCHER points to a directory; refusing to replace it."
fi
if [ -e "$BACKUP_DIR" ] || [ -L "$BACKUP_DIR" ]; then
    fail "temporary backup path already exists: $BACKUP_DIR"
fi
if [ -e "$TEMP_LAUNCHER" ] || [ -L "$TEMP_LAUNCHER" ]; then
    fail "temporary launcher path already exists: $TEMP_LAUNCHER"
fi

# Check the host before touching an existing installation.
if ! command -v python3 >/dev/null 2>&1; then
    fail "CPython 3.10 or newer is required."
fi
if ! python3 -I -c 'import platform, sys; raise SystemExit(platform.python_implementation() != "CPython" or sys.version_info < (3, 10))'; then
    fail "CPython 3.10 or newer is required."
fi

mkdir -p "$SPORK_HOME" "$BIN_DIR"

had_previous=false
committed=false

cleanup() {
    status=$?
    trap - 0 1 2 15
    set +e
    rm -f "$TEMP_LAUNCHER"
    if [ "$committed" != true ]; then
        rm -rf "$VENV_DIR"
        if [ "$had_previous" = true ] && [ -d "$BACKUP_DIR" ]; then
            mv "$BACKUP_DIR" "$VENV_DIR"
            printf '%s\n' "The previous Spork installation was restored." >&2
        fi
    fi
    exit "$status"
}

trap cleanup 0
trap 'exit 129' 1
trap 'exit 130' 2
trap 'exit 143' 15

printf '%s\n' "Installing Spork to $SPORK_HOME"

# Move the old managed environment aside. It is deleted only after the new
# environment and launcher have both been verified and installed.
if [ -d "$VENV_DIR" ]; then
    printf '%s\n' "   Moving the previous environment aside..."
    mv "$VENV_DIR" "$BACKUP_DIR"
    had_previous=true
fi

printf '%s\n' "   Creating a fresh virtual environment..."
if ! python3 -I -m venv "$VENV_DIR"; then
    fail "could not create the virtual environment."
fi

# --isolated ignores user pip configuration and PIP_* environment variables.
# The explicit index prevents an unexpected package source from being used.
printf '%s\n' "   Updating pip from PyPI..."
if ! "$VENV_DIR/bin/python" -I -m pip --isolated --disable-pip-version-check \
    install --quiet --no-input --upgrade --index-url "$PYPI_URL" pip; then
    fail "could not update pip."
fi

printf '%s\n' "   Installing spork-lang from PyPI..."
if ! "$VENV_DIR/bin/python" -I -m pip --isolated --disable-pip-version-check \
    install --quiet --no-input --no-cache-dir --index-url "$PYPI_URL" spork-lang; then
    fail "could not install spork-lang."
fi

if [ ! -x "$VENV_DIR/bin/spork" ]; then
    fail "the installed package did not provide the spork command."
fi
if ! SPORK_VERSION=$("$VENV_DIR/bin/python" -I -c \
    'from importlib.metadata import version; print(version("spork-lang"))'); then
    fail "could not verify the installed spork-lang version."
fi

# Build a new symlink under a unique name, then replace the old managed
# symlink with one rename. A non-symlink launcher was rejected above.
if ! ln -s "$VENV_DIR/bin/spork" "$TEMP_LAUNCHER"; then
    fail "could not create the command symlink."
fi
if ! mv -f "$TEMP_LAUNCHER" "$LAUNCHER"; then
    fail "could not install the command symlink."
fi

# The new installation is now usable. Keep it in place even if deleting the
# old backup reports a filesystem error.
committed=true

# Remove the old environment rather than accumulating stale Spork packages,
# as promised by the clean installer.
if [ "$had_previous" = true ]; then
    printf '%s\n' "   Removing the previous environment..."
    if ! rm -rf "$BACKUP_DIR"; then
        fail "could not remove the previous environment."
    fi
fi

trap - 0 1 2 15

printf '\n%s\n' "Spork $SPORK_VERSION installed successfully!"
printf '%s\n\n' "   Binary location: $LAUNCHER"

case ":$PATH:" in
    *":$BIN_DIR:"*) ;;
    *) printf '%s\n' "   Warning: $BIN_DIR is not in your PATH."
       printf '%s\n' '   Add this to your shell config: export PATH="$HOME/.local/bin:$PATH"' ;;
esac