package exec

import (
	"context"
	"fmt"
	"io"
	"strings"

	"code.cloudfoundry.org/lager/v3"
	"code.cloudfoundry.org/lager/v3/lagerctx"
	"github.com/concourse/concourse/atc"
	"github.com/concourse/concourse/atc/exec/build"
	"github.com/concourse/concourse/vars"
	"github.com/concourse/concourse/worker/baggageclaim"
	"sigs.k8s.io/yaml"
)

//counterfeiter:generate . TaskConfigSource

// TaskConfigSource is used to determine a Task step's TaskConfig.
type TaskConfigSource interface {
	// FetchConfig returns the TaskConfig, and may have to a task config file out
	// of the artifact.Repository.
	FetchConfig(context.Context, lager.Logger, *build.Repository) (atc.TaskConfig, error)
	Warnings() []string
}

// RawTaskConfigSource is a TaskConfigSource that can also hand back the config
// as it was written, along with a description of where it came from. Interpolating
// those bytes lets a var stand in for a field that is not a string, such as the
// values under container_limits.
type RawTaskConfigSource interface {
	FetchRawConfig(context.Context, lager.Logger, *build.Repository) ([]byte, string, error)
}

// StaticConfigSource represents a statically configured TaskConfig.
type StaticConfigSource struct {
	Config *atc.TaskConfig
}

// FetchConfig returns the configuration.
func (configSource StaticConfigSource) FetchConfig(context.Context, lager.Logger, *build.Repository) (atc.TaskConfig, error) {
	taskConfig := atc.TaskConfig{}
	if configSource.Config != nil {
		taskConfig = *configSource.Config
	}
	return taskConfig, nil
}

func (configSource StaticConfigSource) Warnings() []string {
	return []string{}
}

// FileConfigSource represents a dynamically configured TaskConfig, which will
// be fetched from a specified file in the artifact.Repository.
type FileConfigSource struct {
	ConfigPath string
	Streamer   Streamer
}

// FetchConfig reads the specified file from the artifact.Repository and loads the
// TaskConfig contained therein (expecting it to be YAML format).
//
// The path must be in the format SOURCE_NAME/FILE/PATH.yml. The SOURCE_NAME
// will be used to determine the StreamableArtifactSource in the artifact.Repository to
// stream the file out of.
//
// If the source name is missing (i.e. if the path is just "foo.yml"),
// UnspecifiedArtifactSourceError is returned.
//
// If the specified source name cannot be found, UnknownArtifactSourceError is
// returned.
//
// If the task config file is not found, or is invalid YAML, or is an invalid
// task configuration, the respective errors will be bubbled up.
func (configSource FileConfigSource) FetchConfig(ctx context.Context, logger lager.Logger, repo *build.Repository) (atc.TaskConfig, error) {
	byteConfig, source, err := configSource.FetchRawConfig(ctx, logger, repo)
	if err != nil {
		return atc.TaskConfig{}, err
	}

	return newTaskConfig(byteConfig, source)
}

// FetchRawConfig reads the specified file from the artifact.Repository and
// returns its contents without parsing them.
func (configSource FileConfigSource) FetchRawConfig(ctx context.Context, logger lager.Logger, repo *build.Repository) ([]byte, string, error) {
	segs := strings.SplitN(configSource.ConfigPath, "/", 2)
	if len(segs) != 2 {
		return nil, "", UnspecifiedArtifactSourceError{configSource.ConfigPath}
	}

	sourceName := build.ArtifactName(segs[0])
	filePath := segs[1]

	artifact, _, found := repo.ArtifactFor(sourceName)
	if !found {
		return nil, "", UnknownArtifactSourceError{sourceName, configSource.ConfigPath}
	}
	stream, err := configSource.Streamer.StreamFile(lagerctx.NewContext(ctx, logger), artifact, filePath)
	if err != nil {
		if err == baggageclaim.ErrFileNotFound {
			return nil, "", fmt.Errorf("task config '%s/%s' not found", sourceName, filePath)
		}
		return nil, "", err
	}

	defer stream.Close()

	byteConfig, err := io.ReadAll(stream)
	return byteConfig, configSource.ConfigPath, err
}

// newTaskConfig parses a task config, naming the file it came from when it is known.
func newTaskConfig(byteConfig []byte, source string) (atc.TaskConfig, error) {
	config, err := atc.NewTaskConfig(byteConfig)
	if err != nil {
		if source == "" {
			return atc.TaskConfig{}, fmt.Errorf("failed to create task config from bytes: %s", err)
		}
		return atc.TaskConfig{}, fmt.Errorf("failed to create task config from bytes %s: %s", source, err)
	}

	return config, nil
}

func (configSource FileConfigSource) Warnings() []string {
	return []string{}
}

var _ RawTaskConfigSource = FileConfigSource{}

// BaseResourceTypeDefaultsApplySource applies base resource type defaults to image_source.
type BaseResourceTypeDefaultsApplySource struct {
	ConfigSource  TaskConfigSource
	ResourceTypes atc.ResourceTypes
}

func (configSource BaseResourceTypeDefaultsApplySource) FetchConfig(ctx context.Context, logger lager.Logger, repo *build.Repository) (atc.TaskConfig, error) {
	config, err := configSource.ConfigSource.FetchConfig(ctx, logger, repo)
	if err != nil {
		return config, err
	}

	config.ImageResource.ApplySourceDefaults(configSource.ResourceTypes)

	return config, nil
}

func (configSource BaseResourceTypeDefaultsApplySource) Warnings() []string {
	return []string{}
}

type OverrideContainerLimitsSource struct {
	ConfigSource TaskConfigSource
	Limits       *atc.ContainerLimits
}

// FetchConfig overrides container limits, allowing the user to set container limits required by a task loaded
// from a file by providing them in static configuration.
func (configSource *OverrideContainerLimitsSource) FetchConfig(ctx context.Context, logger lager.Logger, source *build.Repository) (atc.TaskConfig, error) {
	taskConfig, err := configSource.ConfigSource.FetchConfig(ctx, logger, source)
	if err != nil {
		return atc.TaskConfig{}, err
	}

	if configSource.Limits == nil {
		return taskConfig, nil
	}

	if taskConfig.Limits == nil {
		taskConfig.Limits = &atc.ContainerLimits{}
	}

	if configSource.Limits.CPU != nil {
		taskConfig.Limits.CPU = configSource.Limits.CPU
	}

	if configSource.Limits.Memory != nil {
		taskConfig.Limits.Memory = configSource.Limits.Memory
	}

	return taskConfig, nil
}

func (configSource *OverrideContainerLimitsSource) Warnings() []string {
	return make([]string, 0)
}

var _ TaskConfigSource = &OverrideContainerLimitsSource{}

// OverrideParamsConfigSource is used to override params in a config source
type OverrideParamsConfigSource struct {
	ConfigSource TaskConfigSource
	Params       atc.TaskEnv
	WarningList  []string
}

// FetchConfig overrides parameters, allowing the user to set params required by a task loaded
// from a file by providing them in static configuration.
func (configSource *OverrideParamsConfigSource) FetchConfig(ctx context.Context, logger lager.Logger, source *build.Repository) (atc.TaskConfig, error) {
	taskConfig, err := configSource.ConfigSource.FetchConfig(ctx, logger, source)
	if err != nil {
		return atc.TaskConfig{}, err
	}

	if taskConfig.Params == nil {
		taskConfig.Params = atc.TaskEnv{}
	}

	for key, val := range configSource.Params {
		if _, exists := taskConfig.Params[key]; !exists {
			configSource.WarningList = append(configSource.WarningList, fmt.Sprintf("%s was defined in pipeline but missing from task file", key))
		}

		taskConfig.Params[key] = val
	}

	return taskConfig, nil
}

func (configSource OverrideParamsConfigSource) Warnings() []string {
	return configSource.WarningList
}

// InterpolateTemplateConfigSource represents a config source interpolated by template vars
type InterpolateTemplateConfigSource struct {
	ConfigSource  TaskConfigSource
	Vars          []vars.Variables
	ExpectAllKeys bool
}

// FetchConfig returns the interpolated configuration
func (configSource InterpolateTemplateConfigSource) FetchConfig(ctx context.Context, logger lager.Logger, source *build.Repository) (atc.TaskConfig, error) {
	byteConfig, from, err := configSource.fetchByteConfig(ctx, logger, source)
	if err != nil {
		return atc.TaskConfig{}, err
	}

	// process task config using the provided variables
	byteConfig, err = vars.NewTemplateResolver(byteConfig, configSource.Vars).Resolve(configSource.ExpectAllKeys)
	if err != nil {
		return atc.TaskConfig{}, fmt.Errorf("failed to interpolate task config: %s", err)
	}

	return newTaskConfig(byteConfig, from)
}

// fetchByteConfig returns the config to interpolate. When the underlying source
// can hand back the config as written, it is used untouched, so a var may stand
// in for a field the parser would reject before it is resolved. Otherwise the
// config has already been parsed and is marshalled back.
func (configSource InterpolateTemplateConfigSource) fetchByteConfig(ctx context.Context, logger lager.Logger, source *build.Repository) ([]byte, string, error) {
	if rawSource, ok := configSource.ConfigSource.(RawTaskConfigSource); ok {
		return rawSource.FetchRawConfig(ctx, logger, source)
	}

	taskConfig, err := configSource.ConfigSource.FetchConfig(ctx, logger, source)
	if err != nil {
		return nil, "", err
	}

	byteConfig, err := yaml.Marshal(taskConfig)
	if err != nil {
		return nil, "", fmt.Errorf("failed to marshal task config: %s", err)
	}

	return byteConfig, "", nil
}

func (configSource InterpolateTemplateConfigSource) Warnings() []string {
	return []string{}
}

// ValidatingConfigSource delegates to another ConfigSource, and validates its
// task config.
type ValidatingConfigSource struct {
	ConfigSource TaskConfigSource
}

// FetchConfig fetches the config using the underlying ConfigSource, and checks
// that it's valid.
func (configSource ValidatingConfigSource) FetchConfig(ctx context.Context, logger lager.Logger, source *build.Repository) (atc.TaskConfig, error) {
	config, err := configSource.ConfigSource.FetchConfig(ctx, logger, source)
	if err != nil {
		return atc.TaskConfig{}, err
	}

	if err := config.Validate(); err != nil {
		return atc.TaskConfig{}, err
	}

	return config, nil
}

func (configSource ValidatingConfigSource) Warnings() []string {
	return configSource.ConfigSource.Warnings()
}

// UnknownArtifactSourceError is returned when the artifact.ArtifactName specified by the
// path does not exist in the artifact.Repository.
type UnknownArtifactSourceError struct {
	SourceName build.ArtifactName
	ConfigPath string
}

// Error returns a human-friendly error message.
func (err UnknownArtifactSourceError) Error() string {
	return fmt.Sprintf("unknown artifact source: '%s' in file path '%s'", err.SourceName, err.ConfigPath)
}

// UnspecifiedArtifactSourceError is returned when the specified path is of a
// file in the toplevel directory, and so it does not indicate a SourceName.
type UnspecifiedArtifactSourceError struct {
	Path string
}

// Error returns a human-friendly error message.
func (err UnspecifiedArtifactSourceError) Error() string {
	return fmt.Sprintf("config path '%s' does not specify where the file lives", err.Path)
}