#!/usr/bin/env bash
#
# qvm-start - Launch the QEMU VM with all required configuration
#
# This script starts the QVM virtual machine with:
# - KVM acceleration and host CPU passthrough
# - Configurable memory and CPU count
# - Overlay disk backed by base.qcow2 (copy-on-write)
# - SSH port forwarding on auto-selected port
# - 9p mounts for shared caches (cargo, pnpm, sccache)
# - Serial console logging
# - Daemonized execution with PID file
#

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
# Args: $1 - starting port number (default: 2222)
# Returns: available port number on stdout
#
find_available_port() {
    local port="${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++ ))
        (( attempt++ ))
    done
    
    die "Could not find available port after $max_attempts attempts"
}

#
# mount_workspaces - Add virtfs entries for registered workspaces
# Args: $1 - name of array variable to append to
# Usage: mount_workspaces qemu_cmd
#
mount_workspaces() {
    local -n cmd_array=$1
    
    # Check if workspaces registry exists
    if [[ ! -f "$QVM_WORKSPACES_FILE" ]]; then
        log_info "No workspaces registry found, skipping workspace mounts"
        return 0
    fi
    
    # Check if file is empty or invalid JSON
    if [[ ! -s "$QVM_WORKSPACES_FILE" ]]; then
        log_info "Workspaces registry is empty, skipping workspace mounts"
        return 0
    fi
    
    # Parse workspaces and add virtfs entries
    local workspace_count
    workspace_count=$(jq -r 'length' "$QVM_WORKSPACES_FILE" 2>/dev/null || echo "0")
    
    if [[ "$workspace_count" -eq 0 ]]; then
        log_info "No workspaces registered, skipping workspace mounts"
        return 0
    fi
    
    log_info "Mounting $workspace_count workspace(s)..."
    
    # Iterate through workspaces and add virtfs entries
    local i=0
    while (( i < workspace_count )); do
        local path mount_tag
        path=$(jq -r ".[$i].path" "$QVM_WORKSPACES_FILE")
        mount_tag=$(jq -r ".[$i].mount_tag" "$QVM_WORKSPACES_FILE")
        
        if [[ -z "$path" || -z "$mount_tag" || "$path" == "null" || "$mount_tag" == "null" ]]; then
            log_warn "Skipping invalid workspace entry at index $i"
            (( i++ ))
            continue
        fi
        
        # Verify path exists
        if [[ ! -d "$path" ]]; then
            log_warn "Workspace path does not exist: $path (skipping)"
            (( i++ ))
            continue
        fi
        
        log_info "  - $path -> $mount_tag"
        cmd_array+=(-virtfs "local,path=$path,mount_tag=$mount_tag,security_model=mapped-xattr,trans=virtio,version=9p2000.L,msize=104857600")
        
        (( i++ ))
    done
}

#
# 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
    
    if [[ ! -f "$QVM_BASE_IMAGE" ]]; then
        log_info "First run detected - building base image..."
        log_info "This may take several minutes."
        
        # Call qvm-rebuild to build the image
        SCRIPT_DIR="$(dirname "$0")"
        if ! "$SCRIPT_DIR/qvm-rebuild"; then
            die "Failed to build base image. Run 'qvm rebuild' manually to debug."
        fi
    fi
    
    # Create overlay image if it doesn't exist
    if [[ ! -f "$QVM_OVERLAY" ]]; then
        log_info "Creating overlay disk..."
        if ! qemu-img create -f qcow2 -b "$QVM_BASE_IMAGE" -F qcow2 "$QVM_OVERLAY"; then
            die "Failed to create overlay disk"
        fi
    else
        log_info "Using existing overlay disk"
    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="${QVM_MEMORY:-8G}"
    local cpus="${QVM_CPUS:-4}"
    log_info "VM resources: ${memory} memory, ${cpus} CPUs"
    
    # Build QEMU command
    local qemu_cmd=(
        qemu-system-x86_64
        -enable-kvm
        -cpu host
        -m "$memory"
        -smp "$cpus"
        
        # Overlay disk (virtio for performance)
        -drive "file=$QVM_OVERLAY,if=virtio,format=qcow2"
        
        # User-mode networking with SSH port forward
        -netdev "user,id=net0,hostfwd=tcp::${ssh_port}-:22"
        -device "virtio-net-pci,netdev=net0"
        
        # 9p mounts for shared caches (security_model=mapped-xattr for proper permissions)
        -virtfs "local,path=$QVM_CARGO_HOME,mount_tag=cargo_home,security_model=mapped-xattr,trans=virtio,version=9p2000.L,msize=104857600"
        -virtfs "local,path=$QVM_CARGO_TARGET,mount_tag=cargo_target,security_model=mapped-xattr,trans=virtio,version=9p2000.L,msize=104857600"
        -virtfs "local,path=$QVM_PNPM_STORE,mount_tag=pnpm_store,security_model=mapped-xattr,trans=virtio,version=9p2000.L,msize=104857600"
        -virtfs "local,path=$QVM_SCCACHE,mount_tag=sccache,security_model=mapped-xattr,trans=virtio,version=9p2000.L,msize=104857600"
    )
    
    # Add workspace mounts from registry
    mount_workspaces qemu_cmd
    
    # Continue building QEMU command
    qemu_cmd+=(
        # Serial console to log file
        -serial "file:$QVM_SERIAL_LOG"
        
        # No graphics
        -nographic
        
        # Daemonize with PID file
        -daemonize
        -pidfile "$QVM_PID_FILE"
    )
    
    # Launch QEMU
    log_info "Launching QEMU..."
    if ! "${qemu_cmd[@]}"; then
        cleanup_on_failure
        die "Failed to start QEMU"
    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" 60; then
        cleanup_on_failure
        die "VM started but SSH did not become available"
    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 "$@"