package chart

import (
	"archive/tar"
	"compress/gzip"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	"github.com/kubernetes/deployment-manager/log"
)

const (
	preTemplates string = "templates/"
	preHooks     string = "hooks/"
	preDocs      string = "docs/"
)

// Chart represents a complete chart.
//
// A chart consists of the following parts:
//
// 	- Chart.yaml: In code, we refer to this as the Chartfile
// 	- templates/*: The template directory
// 	- README.md: Optional README file
// 	- LICENSE: Optional license file
// 	- hooks/: Optional hooks registry
//	- docs/: Optional docs directory
//
// Packed charts are stored in gzipped tar archives (.tgz). Unpackaged charts
// are directories where the directory name is the Chartfile.Name.
//
// Optionally, a chart might also locate a provenance (.prov) file that it
// can use for cryptographic signing.
type Chart interface {
	// Chartfile resturns a *Chartfile for this chart.
	Chartfile() *Chartfile
	// Dir returns a directory where the chart can be accessed.
	Dir() string

	Close() error
}

type dirChart struct {
	chartfile *Chartfile
}

func (d *dirChart) Chartfile() *Chartfile {
	return d.chartfile
}

func (d *dirChart) Dir() string {
	return "."
}

func (d *dirChart) Close() error {
	return nil
}

type tarChart struct {
	chartfile *Chartfile
	tmpDir    string
}

func (t *tarChart) Chartfile() *Chartfile {
	return t.chartfile
}

func (t *tarChart) Dir() string {
	return "."
}

func (t *tarChart) Close() error {
	// Remove the temp directory.
	return os.RemoveAll(t.tmpDir)
}

// LoadDir loads an entire chart from a directory.
//
// This includes the Chart.yaml (*Chartfile) and all of the manifests.
//
// If you are just reading the Chart.yaml file, it is substantially more
// performant to use LoadChartfile.
func LoadDir(chart string) (Chart, error) {
	if fi, err := os.Stat(chart); err != nil {
		return nil, err
	} else if !fi.IsDir() {
		return nil, fmt.Errorf("Chart %s is not a directory.", chart)
	}

	cf, err := LoadChartfile(filepath.Join(chart, "Chart.yaml"))
	if err != nil {
		return nil, err
	}

	c := &dirChart{
		chartfile: cf,
	}

	return c, nil
}

// Load loads a chart from a chart archive.
//
// A chart archive is a gzipped tar archive that follows the Chart format
// specification.
func Load(archive string) (Chart, error) {
	if fi, err := os.Stat(archive); err != nil {
		return nil, err
	} else if fi.IsDir() {
		return nil, errors.New("cannot load a directory with chart.Load()")
	}

	raw, err := os.Open(archive)
	if err != nil {
		return nil, err
	}
	defer raw.Close()

	unzipped, err := gzip.NewReader(raw)
	if err != nil {
		return nil, err
	}
	defer unzipped.Close()

	untarred := tar.NewReader(unzipped)
	return loadTar(untarred)
}

func loadTar(r *tar.Reader) (Chart, error) {
	td, err := ioutil.TempDir("", "chart-")
	if err != nil {
		return nil, err
	}
	c := &tarChart{
		chartfile: &Chartfile{},
		tmpDir:    td,
	}

	firstDir := ""

	hdr, err := r.Next()
	for err == nil {
		log.Debug("Reading %s", hdr.Name)

		// This is to prevent malformed tar attacks.
		hdr.Name = filepath.Clean(hdr.Name)

		if firstDir == "" {
			fi := hdr.FileInfo()
			if fi.IsDir() {
				log.Debug("Discovered app named %s", hdr.Name)
				firstDir = hdr.Name
			} else {
				log.Warn("Unexpected file at root of archive: %s", hdr.Name)
			}
		} else if strings.HasPrefix(hdr.Name, firstDir) {
			log.Debug("Extracting %s to %s", hdr.Name, c.tmpDir)

			// We know this has the prefix, so we know there won't be an error.
			rel, _ := filepath.Rel(firstDir, hdr.Name)

			// If tar record is a directory, create one in the tmpdir and return.
			if hdr.FileInfo().IsDir() {
				os.MkdirAll(filepath.Join(c.tmpDir, rel), 0755)
				hdr, err = r.Next()
				continue
			}

			dest := filepath.Join(c.tmpDir, rel)
			f, err := os.Create(filepath.Join(c.tmpDir, rel))
			if err != nil {
				log.Warn("Could not create %s: %s", dest, err)
				hdr, err = r.Next()
				continue
			}
			if _, err := io.Copy(f, r); err != nil {
				log.Warn("Failed to copy %s: %s", dest, err)
			}
			f.Close()
		} else {
			log.Warn("Unexpected file outside of chart: %s", hdr.Name)
		}
		hdr, err = r.Next()
	}

	if err != nil && err != io.EOF {
		log.Warn("Unexpected error reading tar: %s", err)
		c.Close()
		return c, err
	}
	log.Info("Reached end of Tar file")

	return c, nil
}