package spec

import "time"

// ImageMode decides how the container image reaches the target host.
type ImageMode string

const (
	// ImageAuto pulls from a registry when the reference looks pullable and
	// falls back to streaming the image layers otherwise.
	ImageAuto ImageMode = "auto"
	// ImagePull always runs `docker pull` on the target.
	ImagePull ImageMode = "pull"
	// ImageStream always transfers `docker save` output.
	ImageStream ImageMode = "stream"
	// ImageSkip assumes the image is already present on the target.
	ImageSkip ImageMode = "skip"
)

// ConflictPolicy decides what to do when the target already has a container,
// volume or network with the same name.
type ConflictPolicy string

const (
	ConflictFail    ConflictPolicy = "fail"    // abort the item
	ConflictSkip    ConflictPolicy = "skip"    // leave the target object untouched
	ConflictReplace ConflictPolicy = "replace" // remove the target object first
	ConflictRename  ConflictPolicy = "rename"  // create alongside with a suffix
)

// ItemSelection is the per-container answer to "what do you want to migrate?".
// Every data location is opted in or out individually.
type ItemSelection struct {
	ContainerID string `json:"containerId"`

	// Include is the master switch for this container.
	Include bool `json:"include"`

	// NameOverride renames the container on the target.
	NameOverride string `json:"nameOverride,omitempty"`

	// MigrateImage brings the image across; when false the container is
	// created assuming the image already exists on the target.
	MigrateImage bool      `json:"migrateImage"`
	ImageMode    ImageMode `json:"imageMode"`

	// MigrateNetworks recreates user-defined networks and reattaches them.
	MigrateNetworks bool `json:"migrateNetworks"`
	KeepStaticIPs   bool `json:"keepStaticIps"`
	MigratePorts    bool `json:"migratePorts"`

	// Mounts maps a container-side destination path to how it is handled.
	Mounts map[string]MountSelection `json:"mounts"`

	// StartAfter starts the container on the target once restored.
	StartAfter bool `json:"startAfter"`
	// StopSourceDuringCopy stops the source container for the duration of the
	// data copy so the files are consistent, then restores its former state.
	StopSourceDuringCopy bool `json:"stopSourceDuringCopy"`
	// StopSourceAfter leaves the source container stopped once the migration
	// succeeded, so the two hosts do not both serve the same workload.
	StopSourceAfter bool `json:"stopSourceAfter"`
}

// MountAction is what to do with one data location.
type MountAction string

const (
	// MountActionCopy recreates the mount and copies its contents.
	MountActionCopy MountAction = "copy"
	// MountActionStructure recreates the mount (volume or host directory) but
	// leaves it empty.
	MountActionStructure MountAction = "structure"
	// MountActionSkip drops the mount from the target container entirely.
	MountActionSkip MountAction = "skip"
)

// MountSelection is the per-mount answer, including an optional relocation of
// a bind mount to a different path on the target host.
type MountSelection struct {
	Action MountAction `json:"action"`
	// TargetSource relocates a bind mount on the target host. Empty keeps the
	// source path. Ignored for volumes.
	TargetSource string `json:"targetSource,omitempty"`
	// TargetName renames a named volume on the target. Empty keeps the name.
	TargetName string `json:"targetName,omitempty"`
}

// Options are the settings shared by every item in one migration run.
type Options struct {
	Conflict     ConflictPolicy `json:"conflict"`
	RenameSuffix string         `json:"renameSuffix,omitempty"` // used by ConflictRename, default "-migrated"

	// Compress gzips data and image streams. Requires gzip on the target for
	// SSH mode; always safe for package mode.
	Compress bool `json:"compress"`
	// CompressLevel is 1..9, defaulting to 1 (fast) because these transfers
	// are usually bound by disk and network, not CPU.
	CompressLevel int `json:"compressLevel"`

	// DryRun performs every check and prints every command without changing
	// anything on the target.
	DryRun bool `json:"dryRun"`

	// Parallelism is how many containers migrate at once.
	Parallelism int `json:"parallelism"`

	// VerifyAfter re-inspects each container on the target and compares the
	// resulting spec against the source.
	VerifyAfter bool `json:"verifyAfter"`
}

// DefaultOptions returns the options used when the UI has not overridden them.
func DefaultOptions() Options {
	return Options{
		Conflict:      ConflictFail,
		RenameSuffix:  "-migrated",
		Compress:      true,
		CompressLevel: 1,
		Parallelism:   1,
		VerifyAfter:   true,
	}
}

// DefaultSelection builds the "migrate everything" answer for a container,
// which is what the UI presents before the user changes anything.
func DefaultSelection(c *Container) ItemSelection {
	sel := ItemSelection{
		ContainerID:          c.ID,
		Include:              false,
		MigrateImage:         true,
		ImageMode:            ImageAuto,
		MigrateNetworks:      true,
		KeepStaticIPs:        false,
		MigratePorts:         true,
		Mounts:               map[string]MountSelection{},
		StartAfter:           c.State == "running",
		StopSourceDuringCopy: true,
		StopSourceAfter:      true,
	}
	for _, m := range c.Mounts {
		action := MountActionCopy
		if m.Kind == MountTmpfs {
			action = MountActionStructure
		}
		sel.Mounts[m.Destination] = MountSelection{Action: action}
	}
	return sel
}

// Plan is a complete migration request: what to move, where, and how.
type Plan struct {
	Items   []ItemSelection `json:"items"`
	Options Options         `json:"options"`
	// Target is the SSH connection id for host-to-host mode. Empty means the
	// plan produces an offline package instead.
	Target string `json:"target,omitempty"`
	// PackageName is the base name of the produced package (package mode).
	PackageName string `json:"packageName,omitempty"`
}

// Manifest is written into an offline migration package. It is descriptive:
// the generated install.sh is self-contained and does not parse it.
type Manifest struct {
	FormatVersion int       `json:"formatVersion"`
	CreatedAt     time.Time `json:"createdAt"`
	CreatedBy     string    `json:"createdBy"`
	SourceHost    string    `json:"sourceHost"`
	DockerVersion string    `json:"dockerVersion"`

	Containers []Container     `json:"containers"`
	Volumes    []Volume        `json:"volumes"`
	Networks   []Network       `json:"networks"`
	Items      []ItemSelection `json:"items"`
	Options    Options         `json:"options"`

	// Payloads lists every data file in the package with its checksum, so the
	// installer can verify the archive survived the trip.
	Payloads []Payload `json:"payloads"`
}

// Payload is one file inside a migration package.
type Payload struct {
	Path        string `json:"path"` // relative to the package root
	Kind        string `json:"kind"` // "image" | "mount"
	Container   string `json:"container,omitempty"`
	Destination string `json:"destination,omitempty"` // mount destination it restores
	Image       string `json:"image,omitempty"`
	Bytes       int64  `json:"bytes"`
	SHA256      string `json:"sha256"`
	Compressed  bool   `json:"compressed"`
}