package apiGatewayDeploy

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"encoding/base64"
	"path"
	"errors"
	"io/ioutil"
	"time"
)

const (
	DOWNLOAD_ATTEMPTS = 3
)

var (
	downloadMultiplier = 10 * time.Second
)

type systemBundle struct {
	URI string `json:"uri"`
}

type dependantBundle struct {
	URI   string `json:"uri"`
	Scope string `json:"scope"`
	Org string   `json:"org"`
	Env string   `json:"env"`
}

type bundleManifest struct {
	SysBun systemBundle      `json:"system"`
	DepBun []dependantBundle `json:"bundles"`
}

// event bundle
type bundle struct {
	BundleID string  `json:"bundleId"`
	URI      string  `json:"uri"`
	Scope    string  `json:"scope"`
	Org      string  `json:"org"`
	Env      string  `json:"env"`
}

// event deployment
type deployment struct {
	DeploymentID string   `json:"deploymentId"`
	System       bundle   `json:"system"`
	Bundles      []bundle `json:"bundles"`
}

type deploymentErrorDetail struct {
	ErrorCode int    `json:"errorCode"`
	Reason    string `json:"reason"`
	BundleID  string `json:"bundleId"`
}

type deploymentErrorResponse struct {
	ErrorCode    int                     `json:"errorCode"`
	Reason       string                  `json:"reason"`
	ErrorDetails []deploymentErrorDetail `json:"bundleErrors"`
}

type deploymentResponse struct {
	Status string                  `json:"status"`
	Error  deploymentErrorResponse `json:"error"`
}

// retrieveBundle retrieves bundle data from a URI
func getBundleReader(uriString string) (io.ReadCloser, error) {

	uri, err := url.Parse(uriString)
	if err != nil {
		return nil, fmt.Errorf("DownloadFileUrl: Failed to parse urlStr: %s", uriString)
	}

	// todo: Temporary blind bundle download, Bundle storage TBD

	// assume it's a file if no scheme
	if uri.Scheme == "" || uri.Scheme == "file" {
		f, err := os.Open(uri.Path)
		if err != nil {
			return nil, err
		}
		return f, nil
	}

	// some random uri, try to GET it
	res, err := http.Get(uriString)
	if err != nil {
		return nil, err
	}
	if res.StatusCode != 200 {
		return nil, fmt.Errorf("Bundle uri %s failed with status %s", uriString, res.StatusCode)
	}
	return res.Body, nil
}

// check if already exists and skip
func prepareBundle(depID string, bun bundle) error {

	bundleFile := getBundleFilePath(depID, bun.URI)
	bundleDir := path.Dir(bundleFile)

	downloadBundle := func() (fileName string, err error) {

		log.Debugf("Downloading bundle: %s", bun.URI)

		var tempFile *os.File
		tempFile, err = ioutil.TempFile(bundleDir, "download")
		if err != nil {
			log.Errorf("Unable to create temp file: %v", err)
			return
		}
		fileName = tempFile.Name()

		var bundleReader io.ReadCloser
		bundleReader, err = getBundleReader(bun.URI)
		if err != nil {
			log.Errorf("Unable to retrieve bundle %s: %v", bun.URI, err)
			return
		}
		defer bundleReader.Close()

		_, err = io.Copy(tempFile, bundleReader)
		if err != nil {
			log.Errorf("Unable to write bundle %s: %v", tempFile, err)
		}

		return
	}

	// retry
	var tempFile string
	var err error
	for i := 1; i <= DOWNLOAD_ATTEMPTS; i++ {
		tempFile, err = downloadBundle()
		if err == nil {
			break
		}
		if tempFile != "" {
			os.Remove(tempFile)
		}

		// simple back-off, we could potentially be more sophisticated
		retryIn := time.Duration(i) * downloadMultiplier
		log.Debugf("will retry download in %s", retryIn)
		time.Sleep(retryIn)
	}

	if err != nil {
		log.Errorf("failed %s download attempts. aborting.", DOWNLOAD_ATTEMPTS)
		return err
	}

	err = os.Rename(tempFile, bundleFile)
	if err != nil {
		log.Errorf("Unable to rename temp bundle file %s to %s: %s", tempFile, bundleFile, err)
		os.Remove(tempFile)
		return err
	}

	return nil
}

func getDeploymentFilesPath(depID string) string {
	return path.Join(bundlePath, depID)
}

func getBundleFilePath(depID string, bundleURI string) string {
	return path.Join(getDeploymentFilesPath(depID), base64.StdEncoding.EncodeToString([]byte(bundleURI)))
}

// returns first bundle download error
// all bundles will be attempted regardless of errors, in the future we could retry
func prepareDeployment(depID string, dep deployment) error {

	log.Debugf("preparing deployment: %s", depID)

	err := insertDeployment(depID, dep)
	if err != nil {
		log.Errorf("insert deployment failed: %v", err)
		return err
	}

	deploymentPath := getDeploymentFilesPath(depID)
	err = os.MkdirAll(deploymentPath, 0700)
	if err != nil {
		log.Errorf("Deployment dir creation failed: %v", err)
		return err
	}

	// download bundles and store them locally
	errorsChan := make(chan error, len(dep.Bundles))
	for i := range dep.Bundles {
		bun := dep.Bundles[i]
		go func() {
			err := prepareBundle(depID, bun)
			errorsChan <- err
			if err != nil {
				id := string(i)
				err = updateBundleStatus(db, depID, id, DEPLOYMENT_STATE_ERR_APID, ERROR_CODE_TODO, err.Error())
				if err != nil {
					log.Errorf("Update bundle %s:%s status failed: %v", depID, id, err)
				}
			}
		}()
	}

	// fail fast on first error, otherwise wait for completion
	for range dep.Bundles {
		err := <-errorsChan
		if err != nil {
			updateDeploymentStatus(db, depID, DEPLOYMENT_STATE_ERR_APID, ERROR_CODE_TODO)
			return err
		}
	}

	return updateDeploymentStatus(db, depID, DEPLOYMENT_STATE_READY, 0)
}

func parseManifest(manifestString string) (dep deployment, err error) {
	err = json.Unmarshal([]byte(manifestString), &dep)
	if err != nil {
		log.Errorf("JSON decoding Manifest failed: %v", err)
		return
	}

	// validate manifest
	if dep.System.URI == "" {
		err = errors.New("system bundle 'uri' is required")
		return
	}
	for _, bun := range dep.Bundles {
		if bun.BundleID == "" {
			err = errors.New("bundle 'bundleId' is required")
			return
		}
		if bun.URI == "" {
			err = errors.New("bundle 'uri' is required")
			return
		}
		if bun.Scope == "" {
			err = errors.New("bundle 'scope' is required")
			return
		}
	}

	return
}