package gitea

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"strings"
	"time"

	"golang.org/x/sync/semaphore"
)

type APIClient struct {
	urlBase string
	orgName string
	token   string
	apiSem  *semaphore.Weighted
}

// NewAPIClient creates a new Gitea API client for a single Gitea organization.
// Set maxConnections to 0 for unlimited concurrent API calls.
func NewAPIClient(urlBase string, orgName string, token string, maxConnections int64) *APIClient {

	if !strings.HasSuffix(urlBase, `/`) {
		urlBase += `/`
	}

	ret := &APIClient{
		urlBase: urlBase,
		orgName: orgName,
		token:   token,
	}

	if maxConnections == 0 { // unlimited
		ret.apiSem = semaphore.NewWeighted(99999)
	} else {
		ret.apiSem = semaphore.NewWeighted(maxConnections)
	}

	return ret
}

func (ac *APIClient) PopulateCommitInfo(ctx context.Context, rr *Repo) error {

	// The most recent commit will be the head of one of the branches (easy to find)

	brs, err := ac.Branches(ctx, rr.Name)
	if err != nil {
		return err

	} else {

		NewestCommit := time.Unix(0, 0) // sentinel
		for _, br := range brs {
			if br.Commit.Timestamp.After(NewestCommit) {
				NewestCommit = br.Commit.Timestamp
			}
		}
		if !NewestCommit.Equal(time.Unix(0, 0)) {
			rr.NewestCommit = NewestCommit // replace it
		}
	}

	return nil
}

func (ac *APIClient) PopulateTopics(ctx context.Context, rr *Repo) error {
	t, err := ac.topicsForRepo(ctx, rr.Name)
	if err != nil {
		return err
	}

	rr.Topics = t
	return nil
}

func (ac *APIClient) PopulateImages(ctx context.Context, rr *Repo) error {
	img, err := ac.ImageFilesForRepo(ctx, rr.Name)
	if err != nil {
		return err
	}

	rr.Images = img
	return nil
}

func (ac *APIClient) apiRequest(ctx context.Context, endpoint string, target interface{}) error {
	err := ac.apiSem.Acquire(ctx, 1)
	if err != nil {
		return err // e.g. ctx closed
	}
	defer ac.apiSem.Release(1)

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, ac.urlBase+endpoint, nil)
	if err != nil {
		return err
	}

	if ac.token != "" {
		req.Header.Set(`Authorization`, `token `+ac.token)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		return fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	err = json.NewDecoder(resp.Body).Decode(target)
	if err != nil {
		return err
	}

	return nil
}

func (ac *APIClient) Branches(ctx context.Context, repo string) ([]Branch, error) {
	var branches []Branch

	err := ac.apiRequest(ctx, `api/v1/repos/`+url.PathEscape(ac.orgName)+`/`+url.PathEscape(repo)+`/branches`, &branches)
	if err != nil {
		return nil, err // e.g. ctx closed
	}

	return branches, nil
}

func (ac *APIClient) commitsPage(ctx context.Context, repo, ref string, page, limit int) ([]CommitListEntry, error) {
	var ret []CommitListEntry

	err := ac.apiRequest(ctx, fmt.Sprintf(`api/v1/repos/%s/%s/commits?page=%d&limit=%d`, url.PathEscape(ac.orgName), url.PathEscape(repo), page, limit), &ret)
	if err != nil {
		return nil, err // e.g. ctx closed
	}

	return ret, nil
}

func (ac *APIClient) Commits(ctx context.Context, repo, ref string) ([]CommitListEntry, error) {
	var ret []CommitListEntry

	nextPage := 1 // Counting starts at 1
	for {
		page, err := ac.commitsPage(ctx, repo, ref, nextPage, 300)
		if err != nil {
			return nil, err
		}

		if len(page) == 0 && len(ret) > 0 {
			break // Found enough already
		}

		ret = append(ret, page...)
		nextPage += 1
	}

	if len(ret) == 0 {
		return nil, fmt.Errorf("no commits found")
	}

	return ret, nil
}

// reposPage gets a single page of the list of Git repositories in this organisation.
func (ac *APIClient) reposPage(ctx context.Context, page, limit int) ([]Repo, error) {
	var repos []Repo

	err := ac.apiRequest(ctx, `api/v1/orgs/`+url.PathEscape(ac.orgName)+fmt.Sprintf(`/repos?page=%d&limit=%d`, page, limit), &repos)
	if err != nil {
		return nil, err
	}

	return repos, nil
}

// repos gets a list of Git repositories in this organisation. It may have to
// make multiple network requests.
func (ac *APIClient) Repos(ctx context.Context) ([]Repo, error) {
	// Seems like gitea-1.13.0-rc1 returns 30 results by default, and supports up to a limit of 100
	// Make a much larger request

	ret := make([]Repo, 0)

	nextPage := 1 // Counting starts at 1
	for {
		page, err := ac.reposPage(ctx, nextPage, 300)
		if err != nil {
			return nil, err
		}

		if len(page) == 0 && len(ret) > 0 {
			break // Found enough already
		}

		ret = append(ret, page...)
		nextPage += 1
	}

	return ret, nil
}

// repoFile gets a single file from the default branch of the git repository
// Usually the default branch is `master`.
func (ac *APIClient) RepoFile(ctx context.Context, repo, filename string) ([]byte, error) {
	var cr ContentsResponse

	err := ac.apiRequest(ctx, `api/v1/repos/`+url.PathEscape(ac.orgName)+`/`+url.PathEscape(repo)+`/contents/`+url.PathEscape(filename), &cr)
	if err != nil {
		return nil, err
	}

	return cr.Content, nil
}

func (ac *APIClient) filesInDirectory(ctx context.Context, repo, dir string) ([]ReaddirEntry, error) {
	err := ac.apiSem.Acquire(ctx, 1)
	if err != nil {
		return nil, err // e.g. ctx closed
	}
	defer ac.apiSem.Release(1)

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, ac.urlBase+`api/v1/repos/`+url.PathEscape(ac.orgName)+`/`+url.PathEscape(repo)+`/contents/`+dir, nil) // n.b. $dir param not escaped
	if err != nil {
		return nil, err
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {

		// "No files found" happens with a HTTP 500/404 error depending on Gitea version. Catch this special case
		if resp.StatusCode == 500 || resp.StatusCode == 404 {
			b, err := ioutil.ReadAll(resp.Body)
			if err != nil {
				return nil, err
			}
			if strings.Contains(string(b), `does not exist`) {
				return []ReaddirEntry{}, nil // no files found
			}
		}

		return nil, fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	var ret []ReaddirEntry
	err = json.NewDecoder(resp.Body).Decode(&ret)
	if err != nil {
		return nil, err
	}

	return ret, nil
}

// ImageFilesForRepo finds documentation images for the repository.
// It searches the top-level directory and the dist/ and doc/ subdirectories.
func (ac *APIClient) ImageFilesForRepo(ctx context.Context, repo string) ([]ReaddirEntry, error) {

	ret := []ReaddirEntry{}

	for _, dirName := range []string{``, `dist`, `doc`} {

		files, err := ac.filesInDirectory(ctx, repo, dirName)
		if err != nil {
			return nil, fmt.Errorf("readdir(%s): %w", dirName, err)
		}

		for _, f := range files {
			if f.isImage() {
				ret = append(ret, f)
			}
		}
	}

	return ret, nil
}

func (ac *APIClient) topicsForRepo(ctx context.Context, repo string) ([]string, error) {
	var tr TopicsResponse

	err := ac.apiRequest(ctx, `api/v1/repos/`+url.PathEscape(ac.orgName)+`/`+url.PathEscape(repo)+`/topics`, &tr)
	if err != nil {
		return nil, err
	}

	return tr.Topics, nil
}

// renderMarkdown calls the remote Gitea server's own markdown renderer.
func (ac *APIClient) RenderMarkdown(ctx context.Context, repoName string, body string) ([]byte, error) {
	err := ac.apiSem.Acquire(ctx, 1)
	if err != nil {
		return nil, err // e.g. ctx closed
	}
	defer ac.apiSem.Release(1)

	jb, err := json.Marshal(MarkdownRequest{
		Context: ac.urlBase + url.PathEscape(ac.orgName) + `/` + url.PathEscape(repoName) + `/src/branch/master`,
		Mode:    "gfm", // magic constant - Github Flavoured Markdown
		Text:    body,
	})
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, ac.urlBase+`api/v1/markdown/`, bytes.NewReader(jb))
	if err != nil {
		return nil, err
	}
	req.Header.Set(`Content-Type`, `application/json`)
	req.Header.Set(`Content-Length`, fmt.Sprintf("%d", len(jb)))

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		return nil, fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	return ioutil.ReadAll(resp.Body)
}

// renderMarkdownRaw calls the remote Gitea server's own markdown renderer.
func (ac *APIClient) renderMarkdownRaw(ctx context.Context, body []byte) ([]byte, error) {
	err := ac.apiSem.Acquire(ctx, 1)
	if err != nil {
		return nil, err // e.g. ctx closed
	}
	defer ac.apiSem.Release(1)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, ac.urlBase+`api/v1/markdown/raw`, bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	req.Header.Set(`Content-Type`, `text/plain`)
	req.Header.Set(`Content-Length`, fmt.Sprintf("%d", len(body)))

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		return nil, fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	return ioutil.ReadAll(resp.Body)
}