// Copyright 2021 The Hugo Authors. All rights reserved.
//
// 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 create

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"math/rand"
	"mime"
	"net/http"
	"net/http/httputil"
	"net/url"
	"path"
	"path/filepath"
	"strings"
	"time"

	"github.com/gohugoio/hugo/common/hugio"
	"github.com/gohugoio/hugo/common/maps"
	"github.com/gohugoio/hugo/common/types"
	"github.com/gohugoio/hugo/identity"
	"github.com/gohugoio/hugo/media"
	"github.com/gohugoio/hugo/resources"
	"github.com/gohugoio/hugo/resources/resource"
	"github.com/mitchellh/mapstructure"
)

type HTTPError struct {
	error
	Data map[string]any

	StatusCode int
	Body       string
}

func responseToData(res *http.Response, readBody bool) map[string]any {
	var body []byte
	if readBody {
		body, _ = io.ReadAll(res.Body)
	}

	m := map[string]any{
		"StatusCode":       res.StatusCode,
		"Status":           res.Status,
		"TransferEncoding": res.TransferEncoding,
		"ContentLength":    res.ContentLength,
		"ContentType":      res.Header.Get("Content-Type"),
	}

	if readBody {
		m["Body"] = string(body)
	}

	return m
}

func toHTTPError(err error, res *http.Response, readBody bool) *HTTPError {
	if err == nil {
		panic("err is nil")
	}
	if res == nil {
		return &HTTPError{
			error: err,
			Data:  map[string]any{},
		}
	}

	return &HTTPError{
		error: err,
		Data:  responseToData(res, readBody),
	}
}

var temporaryHTTPStatusCodes = map[int]bool{
	408: true,
	429: true,
	500: true,
	502: true,
	503: true,
	504: true,
}

// FromRemote expects one or n-parts of a URL to a resource
// If you provide multiple parts they will be joined together to the final URL.
func (c *Client) FromRemote(uri string, optionsm map[string]any) (resource.Resource, error) {
	rURL, err := url.Parse(uri)
	if err != nil {
		return nil, fmt.Errorf("failed to parse URL for resource %s: %w", uri, err)
	}

	method := "GET"
	if s, ok := maps.LookupEqualFold(optionsm, "method"); ok {
		method = strings.ToUpper(s.(string))
	}
	isHeadMethod := method == "HEAD"

	resourceID := calculateResourceID(uri, optionsm)

	_, httpResponse, err := c.cacheGetResource.GetOrCreate(resourceID, func() (io.ReadCloser, error) {
		options, err := decodeRemoteOptions(optionsm)
		if err != nil {
			return nil, fmt.Errorf("failed to decode options for resource %s: %w", uri, err)
		}
		if err := c.validateFromRemoteArgs(uri, options); err != nil {
			return nil, err
		}

		var (
			start          time.Time
			nextSleep      = time.Duration((rand.Intn(1000) + 100)) * time.Millisecond
			nextSleepLimit = time.Duration(5) * time.Second
		)

		for {
			b, retry, err := func() ([]byte, bool, error) {
				req, err := options.NewRequest(uri)
				if err != nil {
					return nil, false, fmt.Errorf("failed to create request for resource %s: %w", uri, err)
				}

				res, err := c.httpClient.Do(req)
				if err != nil {
					return nil, false, err
				}
				defer res.Body.Close()

				if res.StatusCode != http.StatusNotFound {
					if res.StatusCode < 200 || res.StatusCode > 299 {
						return nil, temporaryHTTPStatusCodes[res.StatusCode], toHTTPError(fmt.Errorf("failed to fetch remote resource: %s", http.StatusText(res.StatusCode)), res, !isHeadMethod)
					}
				}

				b, err := httputil.DumpResponse(res, true)
				if err != nil {
					return nil, false, toHTTPError(err, res, !isHeadMethod)
				}

				return b, false, nil
			}()
			if err != nil {
				if retry {
					if start.IsZero() {
						start = time.Now()
					} else if d := time.Since(start) + nextSleep; d >= c.rs.Cfg.Timeout() {
						c.rs.Logger.Errorf("Retry timeout (configured to %s) fetching remote resource.", c.rs.Cfg.Timeout())
						return nil, err
					}
					time.Sleep(nextSleep)
					if nextSleep < nextSleepLimit {
						nextSleep *= 2
					}
					continue
				}
				return nil, err
			}

			return hugio.ToReadCloser(bytes.NewReader(b)), nil

		}
	})
	if err != nil {
		return nil, err
	}
	defer httpResponse.Close()

	res, err := http.ReadResponse(bufio.NewReader(httpResponse), nil)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()

	if res.StatusCode == http.StatusNotFound {
		// Not found. This matches how looksup for local resources work.
		return nil, nil
	}

	var (
		body      []byte
		mediaType media.Type
	)
	// A response to a HEAD method should not have a body. If it has one anyway, that body must be ignored.
	// See https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/HEAD
	if !isHeadMethod && res.Body != nil {
		body, err = io.ReadAll(res.Body)
		if err != nil {
			return nil, fmt.Errorf("failed to read remote resource %q: %w", uri, err)
		}
	}

	filename := path.Base(rURL.Path)
	if _, params, _ := mime.ParseMediaType(res.Header.Get("Content-Disposition")); params != nil {
		if _, ok := params["filename"]; ok {
			filename = params["filename"]
		}
	}

	contentType := res.Header.Get("Content-Type")

	// For HEAD requests we have no body to work with, so we need to use the Content-Type header.
	if isHeadMethod || c.rs.ExecHelper.Sec().HTTP.MediaTypes.Accept(contentType) {
		var found bool
		mediaType, found = c.rs.MediaTypes().GetByType(contentType)
		if !found {
			// A media type not configured in Hugo, just create one from the content type string.
			mediaType, _ = media.FromString(contentType)
		}
	}

	if mediaType.IsZero() {

		var extensionHints []string

		// mime.ExtensionsByType gives a long list of extensions for text/plain,
		// just use ".txt".
		if strings.HasPrefix(contentType, "text/plain") {
			extensionHints = []string{".txt"}
		} else {
			exts, _ := mime.ExtensionsByType(contentType)
			if exts != nil {
				extensionHints = exts
			}
		}

		// Look for a file extension. If it's .txt, look for a more specific.
		if extensionHints == nil || extensionHints[0] == ".txt" {
			if ext := path.Ext(filename); ext != "" {
				extensionHints = []string{ext}
			}
		}

		// Now resolve the media type primarily using the content.
		mediaType = media.FromContent(c.rs.MediaTypes(), extensionHints, body)

	}

	if mediaType.IsZero() {
		return nil, fmt.Errorf("failed to resolve media type for remote resource %q", uri)
	}

	resourceID = filename[:len(filename)-len(path.Ext(filename))] + "_" + resourceID + mediaType.FirstSuffix.FullSuffix
	data := responseToData(res, false)

	return c.rs.New(
		resources.ResourceSourceDescriptor{
			MediaType:   mediaType,
			Data:        data,
			LazyPublish: true,
			OpenReadSeekCloser: func() (hugio.ReadSeekCloser, error) {
				return hugio.NewReadSeekerNoOpCloser(bytes.NewReader(body)), nil
			},
			RelTargetFilename: filepath.Clean(resourceID),
		})
}

func (c *Client) validateFromRemoteArgs(uri string, options fromRemoteOptions) error {
	if err := c.rs.ExecHelper.Sec().CheckAllowedHTTPURL(uri); err != nil {
		return err
	}

	if err := c.rs.ExecHelper.Sec().CheckAllowedHTTPMethod(options.Method); err != nil {
		return err
	}

	return nil
}

func calculateResourceID(uri string, optionsm map[string]any) string {
	if key, found := maps.LookupEqualFold(optionsm, "key"); found {
		return identity.HashString(key)
	}
	return identity.HashString(uri, optionsm)
}

func addDefaultHeaders(req *http.Request) {
	if !hasHeaderKey(req.Header, "User-Agent") {
		req.Header.Add("User-Agent", "Hugo Static Site Generator")
	}
}

func addUserProvidedHeaders(headers map[string]any, req *http.Request) {
	if headers == nil {
		return
	}
	for key, val := range headers {
		vals := types.ToStringSlicePreserveString(val)
		for _, s := range vals {
			req.Header.Add(key, s)
		}
	}
}

func hasHeaderKey(m http.Header, key string) bool {
	_, ok := m[key]
	return ok
}

type fromRemoteOptions struct {
	Method  string
	Headers map[string]any
	Body    []byte
}

func (o fromRemoteOptions) BodyReader() io.Reader {
	if o.Body == nil {
		return nil
	}
	return bytes.NewBuffer(o.Body)
}

func (o fromRemoteOptions) NewRequest(url string) (*http.Request, error) {
	req, err := http.NewRequest(o.Method, url, o.BodyReader())
	if err != nil {
		return nil, err
	}

	// First add any user provided headers.
	if o.Headers != nil {
		addUserProvidedHeaders(o.Headers, req)
	}

	// Then add default headers not provided by the user.
	addDefaultHeaders(req)

	return req, nil
}

func decodeRemoteOptions(optionsm map[string]any) (fromRemoteOptions, error) {
	options := fromRemoteOptions{
		Method: "GET",
	}

	err := mapstructure.WeakDecode(optionsm, &options)
	if err != nil {
		return options, err
	}
	options.Method = strings.ToUpper(options.Method)

	return options, nil
}