#!/bin/bash
# install-bash - install Homebrew bash and set it as the login shell (macOS)
#
# Usage:
#   install-bash
#   install-bash -h
#
# Works on both Intel (/usr/local) and Apple Silicon (/opt/homebrew) Macs
# The actual bash install path is resolved dynamically via `brew --prefix`

_install_bash() (
    local SCRIPT_NAME; SCRIPT_NAME="$(basename "${BASH_SOURCE[0]}")"
    case "${BASH_SOURCE[0]}" in /dev/*|/proc/*) SCRIPT_NAME="" ;; esac
    case "$SCRIPT_NAME" in ""|bash|sh|zsh|dash) SCRIPT_NAME="install-bash" ;; esac

    _show_help() {
        echo "NAME"
        echo "  $SCRIPT_NAME - install Homebrew bash and set it as the login shell"
        echo "SYNOPSIS"
        echo "  $SCRIPT_NAME"
        echo "  $SCRIPT_NAME -h"
        echo "DESCRIPTION"
        echo "  Performs the following steps (skipping any already completed):"
        echo "    1. Install Homebrew if not present"
        echo "    2. Install bash via \`brew install bash\`"
        echo "    3. Add the new bash to /etc/shells (requires sudo)"
        echo "    4. Set the current user's shell via \`chsh\` (permanent login-shell change)"
        echo "    5. Append \`brew shellenv\` output to ~/.bash_profile if not already present"
        echo ""
        echo "  The install location is resolved dynamically via \`brew --prefix\`, so the"
        echo "  script works on both Intel (/usr/local) and Apple Silicon (/opt/homebrew)."
        echo "PRECONDITIONS"
        echo "  - macOS only (uses Homebrew, chsh, and /etc/shells)"
        echo "  - sudo access (for editing /etc/shells)"
        echo "  - chsh changes the login shell permanently; revert with \`chsh -s /bin/zsh\`"
        echo "OPTIONS"
        echo "  -h, --help    Show this help message"
        echo "EXIT STATUS"
        echo "  0  Success"
        echo "  1  Runtime failure (install step failed, sudo/chsh rejection, etc.)"
        echo "  2  Precondition error (not running on macOS)"
        echo "DEPENDENCIES"
        echo "  curl, sudo, chsh, uname"
    }

    _error() { echo "[ERR][$SCRIPT_NAME] $*" >&2; }

    case "$1" in
        -h|--help) _show_help; return 0 ;;
    esac

    # Prefix messages for clarity
    local px="[$SCRIPT_NAME]"

    # macOS-only check
    local os; os="$(uname -s)"
    if [ "$os" != "Darwin" ]; then
        _error "macOS only (detected: $os)"
        return 2
    fi

    # Install Homebrew
    if command -v brew >/dev/null 2>&1; then
        echo "$px Homebrew (brew) is already installed, skipping this step"
    else
        if /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"; then
            echo "$px Installed Homebrew (brew)"
        else
            _error "Homebrew installation failed (\`/bin/bash -c \"\$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)\"\`)"
            return 1
        fi
    fi

    # If brew was just installed (or isn't on PATH yet in this shell), source its
    # shellenv from the standard install location before continuing
    if ! command -v brew >/dev/null 2>&1; then
        if [ -x "/opt/homebrew/bin/brew" ]; then
            eval "$(/opt/homebrew/bin/brew shellenv)"
        elif [ -x "/usr/local/bin/brew" ]; then
            eval "$(/usr/local/bin/brew shellenv)"
        else
            _error "\`brew\` is not on PATH after install"
            return 1
        fi
    fi

    # Install Bash using Homebrew
    if brew install bash; then
        echo "$px Installed Bash via Homebrew (\`brew install bash\`)"
    else
        _error "Failed to install Bash via Homebrew"
        return 1
    fi

    # Resolve the actual bash install path dynamically (Intel vs Apple Silicon)
    local brew_prefix; brew_prefix="$(brew --prefix)"
    if [ -z "$brew_prefix" ]; then
        _error "Failed to resolve Homebrew prefix (\`brew --prefix\`)"
        return 1
    fi
    local bash_path="$brew_prefix/bin/bash"

    # Add to /etc/shells first so `chsh` will allow it
    if grep -qxF "$bash_path" "/etc/shells"; then
        echo "$px \"$bash_path\" already added to /etc/shells, skipping this step"
    else
        # `tee` is required because you can't sudo redirect to a file
        if echo "$bash_path" | sudo tee -a "/etc/shells" >/dev/null; then
            echo "$px Added \"$bash_path\" to /etc/shells"
        else
            _error "Failed to add \"$bash_path\" to /etc/shells (\`echo \"$bash_path\" | sudo tee -a \"/etc/shells\" >/dev/null\`)"
            return 1
        fi
    fi

    # Change user's shell
    if chsh -s "$bash_path"; then
        echo "$px Shell for $USER set to $bash_path"
    else
        _error "Failed to change user's shell (\`chsh -s $bash_path\`)"
        return 1
    fi

    # If brew detects that shellenv has already been eval'd by inspecting $PATH nothing will be printed,
    #  but in this case we want to make sure we get output so we set the path to the bare minimum, for this single command
    local shellenv; shellenv="$(PATH=/usr/bin "$brew_prefix/bin/brew" shellenv)"
    if ! grep -qF "$shellenv" "$HOME/.bash_profile"; then
        if printf '\n%s\n' "$shellenv" >>"$HOME/.bash_profile"; then
            echo "$px Added Homebrew environment setup to ~/.bash_profile (\`brew shellenv\`)"
        else
            _error "Failed to add \`brew shellenv\` output to ~/.bash_profile"
            return 1
        fi
    else
        echo "$px Homebrew environment setup (\`brew shellenv\`) already present in ~/.bash_profile, skipping this step"
    fi
)

_install_bash "$@"
__install_bash_rc=$?
unset -f _install_bash
if [ -n "${BASH_SOURCE[0]}" ] && [ "${BASH_SOURCE[0]}" != "$0" ]; then
    eval "unset __install_bash_rc; return $__install_bash_rc"
fi
eval "unset __install_bash_rc; exit $__install_bash_rc"