#!/usr/bin/env bash
#
# qvm-start - Launch the QVM using the NixOS VM runner
#
# This script starts the QVM virtual machine by:
# - Building the VM if not already built
# - Configuring QEMU options via environment variables
# - Adding 9p mounts for caches and workspaces
# - Starting the VM in the background
# - Waiting for SSH to become available
#

set -euo pipefail

# Source common library
QVM_LIB_DIR="${QVM_LIB_DIR:-$(dirname "$(readlink -f "$0")")/../lib}"
# shellcheck source=lib/common.sh
source "$QVM_LIB_DIR/common.sh"

#
# find_available_port - Find an available TCP port starting from base
#
find_available_port() {
    local port="${1:-2222}"
    local max_attempts=100
    local attempt=0
    
    while (( attempt < max_attempts )); do
        if ! nc -z localhost "$port" 2>/dev/null; then
            echo "$port"
            return 0
        fi
        (( port++ )) || true
        (( attempt++ )) || true
    done
    
    die "Could not find available port after $max_attempts attempts"
}

#
# build_qemu_opts - Build QEMU_OPTS environment variable with 9p mounts
#
build_qemu_opts() {
    local ssh_port="$1"
    local opts=""
    
    # 9p mounts for shared caches
    opts+="-virtfs local,path=$QVM_CARGO_HOME,mount_tag=cargo_home,security_model=mapped-xattr "
    opts+="-virtfs local,path=$QVM_CARGO_TARGET,mount_tag=cargo_target,security_model=mapped-xattr "
    opts+="-virtfs local,path=$QVM_PNPM_STORE,mount_tag=pnpm_store,security_model=mapped-xattr "
    opts+="-virtfs local,path=$QVM_SCCACHE,mount_tag=sccache,security_model=mapped-xattr "
    
    # Mount host opencode config if it exists
    if [[ -d "$QVM_HOST_OPENCODE_CONFIG" ]]; then
        log_info "Adding opencode config mount..."
        opts+="-virtfs local,path=$QVM_HOST_OPENCODE_CONFIG,mount_tag=opencode_config,security_model=mapped-xattr "
    fi
    
    # Add workspace mounts from registry
    if [[ -f "$QVM_WORKSPACES_FILE" && -s "$QVM_WORKSPACES_FILE" ]]; then
        local workspace_count
        workspace_count=$(jq -r 'length' "$QVM_WORKSPACES_FILE" 2>/dev/null || echo "0")
        
        if [[ "$workspace_count" -gt 0 ]]; then
            log_info "Adding $workspace_count workspace mount(s)..."
            
            local i=0
            while (( i < workspace_count )); do
                local path mount_tag
                path=$(jq -r ".[$i].host_path" "$QVM_WORKSPACES_FILE")
                mount_tag=$(jq -r ".[$i].mount_tag" "$QVM_WORKSPACES_FILE")
                
                if [[ -n "$path" && -n "$mount_tag" && "$path" != "null" && "$mount_tag" != "null" && -d "$path" ]]; then
                    log_info "  - $path -> $mount_tag"
                    opts+="-virtfs local,path=$path,mount_tag=$mount_tag,security_model=mapped-xattr "
                fi
                
                (( i++ )) || true
            done
        fi
    fi
    
    # Serial console to log file and daemonize
    opts+="-serial file:$QVM_SERIAL_LOG "
    opts+="-display none "
    opts+="-daemonize "
    opts+="-pidfile $QVM_PID_FILE "
    
    echo "$opts"
}

#
# cleanup_on_failure - Clean up state files if VM start fails
#
cleanup_on_failure() {
    log_warn "Cleaning up after failed start..."
    rm -f "$QVM_PID_FILE" "$QVM_SSH_PORT_FILE"
}

#
# main - Main execution flow
#
main() {
    log_info "Starting QVM..."
    
    # Check if VM is already running
    if is_vm_running; then
        log_info "VM is already running"
        local port
        port=$(get_ssh_port)
        echo "SSH available on port: $port"
        echo "Use 'qvm ssh' to connect or 'qvm status' for details"
        exit 0
    fi
    
    # First-run initialization
    ensure_dirs
    
    # Source config file if it exists (sets QVM_MEMORY, QVM_CPUS, etc.)
    # Check system-wide config first, then user config (user overrides system)
    if [[ -f "/etc/xdg/qvm/qvm.conf" ]]; then
        source "/etc/xdg/qvm/qvm.conf"
    fi
    if [[ -f "$QVM_CONFIG_FILE" ]]; then
        source "$QVM_CONFIG_FILE"
    fi
    
    # Check if VM runner exists, build if not
    if [[ ! -L "$QVM_VM_RUNNER" || ! -f "$(readlink -f "$QVM_VM_RUNNER" 2>/dev/null || echo "")" ]]; then
        log_info "First run detected - building VM..."
        log_info "This may take several minutes."
        
        local qvm_rebuild="${QVM_BIN_DIR:-$(dirname "$0")}/qvm-rebuild"
        if ! "$qvm_rebuild"; then
            die "Failed to build VM. Run 'qvm rebuild' manually to debug."
        fi
    fi
    
    # Verify VM runner exists now
    if [[ ! -L "$QVM_VM_RUNNER" ]]; then
        die "VM runner not found at $QVM_VM_RUNNER. Run 'qvm rebuild' first."
    fi
    
    local vm_script
    vm_script=$(readlink -f "$QVM_VM_RUNNER")
    if [[ ! -f "$vm_script" ]]; then
        die "VM runner script not found. Run 'qvm rebuild' to fix."
    fi
    
    # Find available SSH port
    local ssh_port
    ssh_port=$(find_available_port 2222)
    log_info "Using SSH port: $ssh_port"
    
    # Get memory and CPU settings from environment or use defaults
    local memory="${QVM_MEMORY:-30G}"
    local cpus="${QVM_CPUS:-30}"
    log_info "VM resources: ${memory} memory, ${cpus} CPUs"
    
    # Build QEMU options
    local qemu_opts
    qemu_opts=$(build_qemu_opts "$ssh_port")
    
    # Launch VM using the NixOS runner script
    # The runner script respects these environment variables:
    # - QEMU_OPTS: additional QEMU options
    # - NIX_DISK_IMAGE: path to disk image (optional, uses tmpdir by default)
    log_info "Launching VM..."
    
    # Create persistent disk image location if needed
    local disk_image="$QVM_STATE_DIR/qvm-dev.qcow2"
    
    export QEMU_OPTS="$qemu_opts -m $memory -smp $cpus"
    export QEMU_NET_OPTS="hostfwd=tcp::${ssh_port}-:22"
    export NIX_DISK_IMAGE="$disk_image"
    
    # Run VM - the script uses exec with qemu's -daemonize flag, so it returns quickly
    if ! "$vm_script" &>/dev/null; then
        cleanup_on_failure
        die "Failed to start VM"
    fi
    
    # Wait a moment for QEMU to create PID file
    sleep 2
    
    # If PID file wasn't created by our QEMU_OPTS, get it from the background process
    if [[ ! -f "$QVM_PID_FILE" ]]; then
        # Try to find the QEMU process
        local qemu_pid
        qemu_pid=$(pgrep -f "qemu.*qvm-dev" | head -1 || echo "")
        if [[ -n "$qemu_pid" ]]; then
            echo "$qemu_pid" > "$QVM_PID_FILE"
        fi
    fi
    
    # Save SSH port to file
    echo "$ssh_port" > "$QVM_SSH_PORT_FILE"
    
    # Wait for SSH to become available
    if ! wait_for_ssh "$ssh_port" 120; then
        cleanup_on_failure
        die "VM started but SSH did not become available. Check: $QVM_SERIAL_LOG"
    fi
    
    # Success!
    log_info "VM started successfully"
    echo ""
    echo "SSH available on port: $ssh_port"
    echo "Connect with: qvm ssh"
    echo "Check status: qvm status"
    echo "Serial log: $QVM_SERIAL_LOG"
}

# Run main function
main "$@"