#!/bin/bash
set -e

# 🎯 Detect OS & package manager
detect_platform() {
    if [[ "$OSTYPE" == "darwin"* ]]; then
        OS="macos"; PKG_MGR="brew"
        if ! command -v brew &>/dev/null; then
            echo "🍺 Installing Homebrew..."
            /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
            echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> ~/.zprofile
            eval "$(/opt/homebrew/bin/brew shellenv)"
        fi
    elif command -v apt &>/dev/null; then
        OS="debian"; PKG_MGR="apt"
    elif command -v dnf &>/dev/null; then
        OS="rhel"; PKG_MGR="dnf"
    elif command -v yum &>/dev/null; then
        OS="rhel"; PKG_MGR="yum"
    elif command -v pacman &>/dev/null; then
        OS="arch"; PKG_MGR="pacman"
    else
        echo "❌ Unsupported platform"; exit 1
    fi
    echo "✓ Detected $OS ($PKG_MGR)"
}

# 🔐 Install gpg if needed (Debian/Ubuntu)
install_gpg_if_needed() {
    if [[ "$OS" == "debian" ]] && ! command -v gpg &>/dev/null; then
        echo "🔑 Installing gpg..."
        sudo apt update && sudo apt install -y gnupg
    fi
}

# 📦 Add Fish repo (Debian/Ubuntu)
add_fish_repo_debian() {
    echo "• Adding Fish repo..."
    echo 'deb http://download.opensuse.org/repositories/shells:/fish:/release:/4/Debian_12/ /' | \
        sudo tee /etc/apt/sources.list.d/fish.list >/dev/null
    curl -fsSL https://download.opensuse.org/repositories/shells:fish:release:4/Debian_12/Release.key | \
        gpg --dearmor | sudo tee /etc/apt/trusted.gpg.d/fish.gpg > /dev/null
    sudo apt update
}

# 🐟 Install Fish shell
install_fish() {
    echo "• Installing Fish..."
    case "$OS" in
        debian) add_fish_repo_debian; sudo apt install -y fish ;;
        rhel)   sudo $PKG_MGR install -y fish ;;
        arch)   sudo pacman -Sy --noconfirm fish ;;
        macos)  brew install fish ;;
    esac
}

# 🔎 Detect if an update seems available (without doing a refresh)
fish_update_available() {
    case "$PKG_MGR" in
        apt)
            # Compare Installed vs Candidate using current cache (no apt update)
            local installed candidate
            installed="$(dpkg-query -W -f='${Version}\n' fish 2>/dev/null || true)"
            candidate="$(apt-cache policy fish 2>/dev/null | awk '/Candidate:/ {print $2}')"
            [[ -n "$installed" && -n "$candidate" && "$candidate" != "(none)" && "$candidate" != "$installed" ]]
            ;;
        dnf|yum)
            # Fast check; may contact repos briefly but doesn't install
            $PKG_MGR -q check-update fish >/dev/null 2>&1
            [[ $? -eq 100 ]]  # 100 = updates available
            ;;
        pacman)
            # No refresh; just check queued upgrades
            pacman -Qu 2>/dev/null | grep -q '^fish '
            ;;
        brew)
            # No brew update; check current outdated list
            brew outdated --quiet 2>/dev/null | grep -q '^fish$'
            ;;
    esac
}

# ♻️ Update flow (only prompt if an update looks available)
maybe_update_fish() {
    echo "• Checking Fish updates…"
    if fish_update_available; then
        read -rp "A newer Fish appears available. Refresh repos and update now? (y/N): " confirm
        if [[ "$confirm" =~ ^[Yy]$ ]]; then
            case "$PKG_MGR" in
                apt)
                    sudo apt update
                    sudo apt install -y fish && echo "✓ Fish updated"
                    ;;
                dnf|yum)
                    sudo $PKG_MGR check-update || true
                    sudo $PKG_MGR update -y fish && echo "✓ Fish updated"
                    ;;
                pacman)
                    sudo pacman -Sy --noconfirm
                    sudo pacman -S --noconfirm fish && echo "✓ Fish updated"
                    ;;
                brew)
                    brew update
                    brew upgrade fish && echo "✓ Fish updated"
                    ;;
            esac
        else
            echo "✓ Skipped update"
        fi
    else
        echo "✓ No update detected (based on current cache)"
    fi
}

# 🎣 Install Fisher
install_fisher() {
    if fish -c "functions -q fisher" &>/dev/null; then
        echo "✓ Fisher already present"
    else
        echo "• Installing Fisher..."
        # isolate stdin so curl|bash doesnt leak into fish
        fish -c 'curl -sL https://git.io/fisher | source && fisher install jorgebucaran/fisher' </dev/null
    fi
}

# 🧩 Install plugins (idempotent)
install_plugins() {
    local plugins=( jethrokuan/z ilancosman/tide jorgebucaran/nvm.fish )
    local install_list=()
    local installed
    installed="$(fish -c 'fisher list' </dev/null 2>/dev/null || true)"
    for p in "${plugins[@]}"; do
        if ! grep -Fxq "$p" <<<"$installed"; then
            install_list+=("$p")
        fi
    done
    if [[ ${#install_list[@]} -gt 0 ]]; then
        echo "• Installing plugins: ${install_list[*]}"
        fish -c "fisher install ${install_list[*]}" </dev/null
        echo "✓ Plugins installed"
    else
        echo "✓ All requested plugins already installed"
    fi
}

# 🐚 Ask to set Fish as default shell (only if not already)
set_fish_default() {
    local fish_path current_shell
    fish_path="$(command -v fish)"
    current_shell="$(getent passwd "$USER" | cut -d: -f7)"

    if [[ "$current_shell" == "$fish_path" ]]; then
        echo "✓ Fish is already your default shell"
        return
    fi

    read -rp "Set Fish as your default shell? (y/N): " confirm
    if [[ "$confirm" =~ ^[Yy]$ ]]; then
        if ! grep -q "^$fish_path$" /etc/shells; then
            echo "$fish_path" | sudo tee -a /etc/shells >/dev/null
        fi
        chsh -s "$fish_path"
        echo "✓ Fish set as default shell (applies to new sessions)"
    else
        echo "✓ Keeping current default shell"
    fi
}

# 🚀 Main flow
detect_platform
install_gpg_if_needed

if command -v fish &>/dev/null; then
    echo "✓ Fish already installed"
    maybe_update_fish
else
    install_fish
fi

install_fisher
install_plugins
set_fish_default

echo "✓ Fish + Fisher + plugins ready on $OS"