#!/usr/bin/env bash
set -euo pipefail

usage() {
    cat <<'USAGE'
Install ByteLyst shell aliases into your shell startup file.

Usage:
  ./install.sh [--dry-run] [--shell bash|zsh] [--rc-file PATH]

Options:
  --dry-run       Show what would change without writing files.
  --shell SHELL   Override detected shell. Supported: bash, zsh.
  --rc-file PATH  Override the target startup file.
  --help          Show this help.
USAGE
}

die() {
    echo "Error: $*" >&2
    exit 1
}

detect_os() {
    case "$(uname -s)" in
        Darwin) echo "macos" ;;
        Linux) echo "linux" ;;
        *) echo "unknown" ;;
    esac
}

detect_shell() {
    local shell_name
    shell_name="$(basename "${SHELL:-}")"

    case "$shell_name" in
        bash | zsh) echo "$shell_name" ;;
        *)
            if command -v zsh >/dev/null 2>&1; then
                echo "zsh"
            elif command -v bash >/dev/null 2>&1; then
                echo "bash"
            else
                die "could not detect bash or zsh; pass --shell bash or --shell zsh"
            fi
            ;;
    esac
}

default_rc_file() {
    local shell_name="$1"
    local os_name="$2"

    case "$shell_name" in
        zsh)
            echo "$HOME/.zshrc"
            ;;
        bash)
            if [ "$os_name" = "macos" ]; then
                echo "$HOME/.bash_profile"
            else
                echo "$HOME/.bashrc"
            fi
            ;;
        *)
            die "unsupported shell: $shell_name"
            ;;
    esac
}

resolve_alias_dir() {
    local source_path="${BASH_SOURCE[0]}"
    cd -- "$(dirname -- "$source_path")" >/dev/null 2>&1
    pwd -P
}

remove_existing_block() {
    local input_file="$1"
    local output_file="$2"

    awk '
        /^# >>> bytelyst aliases >>>$/ { skip = 1; next }
        /^# <<< bytelyst aliases <<<$/{ skip = 0; next }
        !skip { lines[++count] = $0 }
        END {
            while (count > 0 && lines[count] == "") {
                count--
            }
            for (i = 1; i <= count; i++) {
                print lines[i]
            }
        }
    ' "$input_file" > "$output_file"
}

write_block() {
    local alias_loader="$1"

    cat <<BLOCK
# >>> bytelyst aliases >>>
source "$alias_loader"
# <<< bytelyst aliases <<<
BLOCK
}

dry_run=false
shell_override=""
rc_file=""

while [ "$#" -gt 0 ]; do
    case "$1" in
        --dry-run)
            dry_run=true
            shift
            ;;
        --shell)
            [ "$#" -ge 2 ] || die "--shell requires bash or zsh"
            shell_override="$2"
            shift 2
            ;;
        --rc-file)
            [ "$#" -ge 2 ] || die "--rc-file requires a path"
            rc_file="$2"
            shift 2
            ;;
        --help | -h)
            usage
            exit 0
            ;;
        *)
            die "unknown option: $1"
            ;;
    esac
done

os_name="$(detect_os)"
shell_name="${shell_override:-$(detect_shell)}"

case "$shell_name" in
    bash | zsh) ;;
    *) die "unsupported shell: $shell_name" ;;
esac

alias_dir="$(resolve_alias_dir)"
alias_loader="$alias_dir/_source_all.alias"
[ -f "$alias_loader" ] || die "alias loader not found: $alias_loader"

target_rc="${rc_file:-$(default_rc_file "$shell_name" "$os_name")}"

echo "Detected OS: $os_name"
echo "Target shell: $shell_name"
echo "Target startup file: $target_rc"
echo "Alias loader: $alias_loader"

if [ "$dry_run" = true ]; then
    echo
    echo "Would add or replace this managed block:"
    write_block "$alias_loader"
    exit 0
fi

mkdir -p "$(dirname -- "$target_rc")"
touch "$target_rc"

tmp_file="$(mktemp)"
new_file="$(mktemp)"
trap 'rm -f "$tmp_file" "$new_file"' EXIT

remove_existing_block "$target_rc" "$tmp_file"
{
    cat "$tmp_file"
    if [ -s "$tmp_file" ]; then
        echo
    fi
    write_block "$alias_loader"
} > "$new_file"

if cmp -s "$target_rc" "$new_file"; then
    echo
    echo "ByteLyst aliases are already installed."
    echo "They will be available in new shell sessions."
    echo "To use them in this shell now, run:"
    echo "  source \"$target_rc\""
    exit 0
fi

backup_file="$target_rc.bytelyst-aliases.bak.$(date +%Y%m%d%H%M%S).$$"
cp "$target_rc" "$backup_file"
cat "$new_file" > "$target_rc"

echo
echo "Installed ByteLyst aliases."
echo "Backup created: $backup_file"
echo "They will be available in new shell sessions."
echo "To use them in this shell now, run:"
echo "  source \"$target_rc\""