/*
Copyright 2016 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package vfs

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"strings"
)

// VFSContext is a 'context' for VFS, that is normally a singleton
// but allows us to configure S3 credentials, for example
type VFSContext struct {
	s3Context    *S3Context
	memfsContext *MemFSContext
}

var Context = VFSContext{
	s3Context: NewS3Context(),
}

// ReadLocation reads a file from a vfs URL
// It supports additional schemes which don't (yet) have full VFS implementations:
//   metadata: reads from instance metadata on GCE/AWS
//   http / https: reads from HTTP
func (c *VFSContext) ReadFile(location string) ([]byte, error) {
	if strings.Contains(location, "://") {
		// Handle our special case schemas
		u, err := url.Parse(location)
		if err != nil {
			return nil, fmt.Errorf("error parsing location %q - not a valid URI", location)
		}

		switch u.Scheme {
		case "metadata":
			switch u.Host {
			case "gce":
				httpURL := "http://169.254.169.254/computeMetadata/v1/instance/attributes/" + u.Path
				httpHeaders := make(map[string]string)
				httpHeaders["Metadata-Flavor"] = "Google"
				return c.readHttpLocation(httpURL, httpHeaders)
			case "aws":
				httpURL := "http://169.254.169.254/latest/" + u.Path
				return c.readHttpLocation(httpURL, nil)

			default:
				return nil, fmt.Errorf("unknown metadata type: %q in %q", u.Host, location)
			}

		case "http", "https":
			return c.readHttpLocation(location, nil)
		}

	}

	p, err := c.BuildVfsPath(location)
	if err != nil {
		return nil, err
	}
	return p.ReadFile()
}

func (c *VFSContext) BuildVfsPath(p string) (Path, error) {
	if !strings.Contains(p, "://") {
		return NewFSPath(p), nil
	}

	if strings.HasPrefix(p, "s3://") {
		return c.buildS3Path(p)
	}

	if strings.HasPrefix(p, "memfs://") {
		return c.buildMemFSPath(p)
	}

	return nil, fmt.Errorf("unknown / unhandled path type: %q", p)
}

// readHttpLocation reads an http (or https) url.
// It returns the contents, or an error on any non-200 response.  On a 404, it will return os.ErrNotExist
func (c *VFSContext) readHttpLocation(httpURL string, httpHeaders map[string]string) ([]byte, error) {
	req, err := http.NewRequest("GET", httpURL, nil)
	if err != nil {
		return nil, err
	}
	for k, v := range httpHeaders {
		req.Header.Add(k, v)
	}
	response, err := http.DefaultClient.Do(req)
	if response != nil {
		defer response.Body.Close()
	}
	if err != nil {
		return nil, fmt.Errorf("error fetching %q: %v", httpURL, err)
	}
	body, err := ioutil.ReadAll(response.Body)
	if err != nil {
		return nil, fmt.Errorf("error reading response for %q: %v", httpURL, err)
	}
	if response.StatusCode == 404 {
		return nil, os.ErrNotExist
	}
	if response.StatusCode != 200 {
		return nil, fmt.Errorf("unexpected response code %q for %q: %v", response.Status, httpURL, string(body))
	}
	return body, nil
}

func (c *VFSContext) buildS3Path(p string) (*S3Path, error) {
	u, err := url.Parse(p)
	if err != nil {
		return nil, fmt.Errorf("invalid s3 path: %q", err)
	}

	bucket := strings.TrimSuffix(u.Host, "/")
	if bucket == "" {
		return nil, fmt.Errorf("invalid s3 path: %q", err)
	}

	s3path := newS3Path(c.s3Context, bucket, u.Path)
	return s3path, nil
}

func (c *VFSContext) buildMemFSPath(p string) (*MemFSPath, error) {
	if !strings.HasPrefix(p, "memfs://") {
		return nil, fmt.Errorf("memfs path not recognized: %q", p)
	}
	location := strings.TrimPrefix(p, "memfs://")
	if c.memfsContext == nil {
		// We only initialize this in unit tests etc
		return nil, fmt.Errorf("memfs context not initialized")
	}
	fspath := NewMemFSPath(c.memfsContext, location)
	return fspath, nil
}

func (c *VFSContext) ResetMemfsContext(clusterReadable bool) {
	c.memfsContext = NewMemFSContext()
	if clusterReadable {
		c.memfsContext.MarkClusterReadable()
	}
}