package libpod

import (
	"bufio"
	"fmt"
	"net"
	"path/filepath"
	"sync"

	"github.com/containers/libpod/libpod/define"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
	"k8s.io/client-go/tools/remotecommand"
)

var (
	// Only create each missing runtime once.
	// Creation makes error messages we don't want to duplicate.
	missingRuntimes map[string]*MissingRuntime
	// We need a lock for this
	missingRuntimesLock sync.Mutex
)

// MissingRuntime is used when the OCI runtime requested by the container is
// missing (not installed or not in the configuration file).
type MissingRuntime struct {
	// Name is the name of the missing runtime. Will be used in errors.
	name string
	// exitsDir is the directory for exit files.
	exitsDir string
}

// Get a new MissingRuntime for the given name.
// Requires a libpod Runtime so we can make a sane path for the exits dir.
func getMissingRuntime(name string, r *Runtime) (OCIRuntime, error) {
	missingRuntimesLock.Lock()
	defer missingRuntimesLock.Unlock()

	if missingRuntimes == nil {
		missingRuntimes = make(map[string]*MissingRuntime)
	}

	runtime, ok := missingRuntimes[name]
	if ok {
		return runtime, nil
	}

	// Once for each missing runtime, we want to error.
	logrus.Errorf("OCI Runtime %s is in use by a container, but is not available (not in configuration file or not installed)", name)

	newRuntime := new(MissingRuntime)
	newRuntime.name = name
	newRuntime.exitsDir = filepath.Join(r.config.Engine.TmpDir, "exits")

	missingRuntimes[name] = newRuntime

	return newRuntime, nil
}

// Name is the name of the missing runtime
func (r *MissingRuntime) Name() string {
	return fmt.Sprintf("%s (missing/not available)", r.name)
}

// Path is not available as the runtime is missing
func (r *MissingRuntime) Path() string {
	return "(missing/not available)"
}

// CreateContainer is not available as the runtime is missing
func (r *MissingRuntime) CreateContainer(ctr *Container, restoreOptions *ContainerCheckpointOptions) error {
	return r.printError()
}

// UpdateContainerStatus is not available as the runtime is missing
func (r *MissingRuntime) UpdateContainerStatus(ctr *Container) error {
	return r.printError()
}

// StartContainer is not available as the runtime is missing
func (r *MissingRuntime) StartContainer(ctr *Container) error {
	return r.printError()
}

// KillContainer is not available as the runtime is missing
// TODO: We could attempt to unix.Kill() the PID as recorded in the state if we
// really want to smooth things out? Won't be perfect, but if the container has
// a PID namespace it could be enough?
func (r *MissingRuntime) KillContainer(ctr *Container, signal uint, all bool) error {
	return r.printError()
}

// StopContainer is not available as the runtime is missing
func (r *MissingRuntime) StopContainer(ctr *Container, timeout uint, all bool) error {
	return r.printError()
}

// DeleteContainer is not available as the runtime is missing
func (r *MissingRuntime) DeleteContainer(ctr *Container) error {
	return r.printError()
}

// PauseContainer is not available as the runtime is missing
func (r *MissingRuntime) PauseContainer(ctr *Container) error {
	return r.printError()
}

// UnpauseContainer is not available as the runtime is missing
func (r *MissingRuntime) UnpauseContainer(ctr *Container) error {
	return r.printError()
}

// HTTPAttach is not available as the runtime is missing
func (r *MissingRuntime) HTTPAttach(ctr *Container, httpConn net.Conn, httpBuf *bufio.ReadWriter, streams *HTTPAttachStreams, detachKeys *string, cancel <-chan bool) error {
	return r.printError()
}

// AttachResize is not available as the runtime is missing
func (r *MissingRuntime) AttachResize(ctr *Container, newSize remotecommand.TerminalSize) error {
	return r.printError()
}

// ExecContainer is not available as the runtime is missing
func (r *MissingRuntime) ExecContainer(ctr *Container, sessionID string, options *ExecOptions) (int, chan error, error) {
	return -1, nil, r.printError()
}

// ExecAttachResize is not available as the runtime is missing.
func (r *MissingRuntime) ExecAttachResize(ctr *Container, sessionID string, newSize remotecommand.TerminalSize) error {
	return r.printError()
}

// ExecStopContainer is not available as the runtime is missing.
// TODO: We can also investigate using unix.Kill() on the PID of the exec
// session here if we want to make stopping containers possible. Won't be
// perfect, though.
func (r *MissingRuntime) ExecStopContainer(ctr *Container, sessionID string, timeout uint) error {
	return r.printError()
}

// ExecUpdateStatus is not available as the runtime is missing.
func (r *MissingRuntime) ExecUpdateStatus(ctr *Container, sessionID string) (bool, error) {
	return false, r.printError()
}

// ExecContainerCleanup is not available as the runtime is missing
func (r *MissingRuntime) ExecContainerCleanup(ctr *Container, sessionID string) error {
	return r.printError()
}

// CheckpointContainer is not available as the runtime is missing
func (r *MissingRuntime) CheckpointContainer(ctr *Container, options ContainerCheckpointOptions) error {
	return r.printError()
}

// SupportsCheckpoint returns false as checkpointing requires a working runtime
func (r *MissingRuntime) SupportsCheckpoint() bool {
	return false
}

// SupportsJSONErrors returns false as there is no runtime to give errors
func (r *MissingRuntime) SupportsJSONErrors() bool {
	return false
}

// SupportsNoCgroups returns false as there is no runtime to create containers
func (r *MissingRuntime) SupportsNoCgroups() bool {
	return false
}

// AttachSocketPath does not work as there is no runtime to attach to.
// (Theoretically we could follow ExitFilePath but there is no guarantee the
// container is running and thus has an attach socket...)
func (r *MissingRuntime) AttachSocketPath(ctr *Container) (string, error) {
	return "", r.printError()
}

// ExecAttachSocketPath does not work as there is no runtime to attach to.
// (Again, we could follow ExitFilePath, but no guarantee there is an existing
// and running exec session)
func (r *MissingRuntime) ExecAttachSocketPath(ctr *Container, sessionID string) (string, error) {
	return "", r.printError()
}

// ExitFilePath returns the exit file path for containers.
// Here, we mimic what ConmonOCIRuntime does, because there is a chance that the
// container in question is still running happily (config file modified to
// remove a runtime, for example). We can't find the runtime to do anything to
// the container, but Conmon should still place an exit file for it.
func (r *MissingRuntime) ExitFilePath(ctr *Container) (string, error) {
	if ctr == nil {
		return "", errors.Wrapf(define.ErrInvalidArg, "must provide a valid container to get exit file path")
	}
	return filepath.Join(r.exitsDir, ctr.ID()), nil
}

// RuntimeInfo returns information on the missing runtime
func (r *MissingRuntime) RuntimeInfo() (*define.ConmonInfo, *define.OCIRuntimeInfo, error) {
	ocirt := define.OCIRuntimeInfo{
		Name:    r.name,
		Path:    "missing",
		Package: "missing",
		Version: "missing",
	}
	return nil, &ocirt, nil
}

// Return an error indicating the runtime is missing
func (r *MissingRuntime) printError() error {
	return errors.Wrapf(define.ErrOCIRuntimeNotFound, "runtime %s is missing", r.name)
}
