package main

// remote.go — the `pushremote` command: mirror the active project to a public
// git hosting server (Gitea, GitHub or GitLab), creating the repository via the
// server's REST API when it does not exist yet.
//
// Configuration (in ~/.mgshrc or MGSH_* env):
//
//	remoteurl  = https://git.example.com   base URL of the server
//	remotekey  = <api-token>               personal access token
//	remotetype = gitea|github|gitlab       optional; auto-detected from the URL
//
// The token is used for the API calls and, via an HTTP Basic auth header, for
// the git push. It is never written into the repository's git config.

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"strings"
	"time"
)

type remoteKind int

const (
	kindGitea remoteKind = iota
	kindGitHub
	kindGitLab
)

// detectRemoteKind picks the provider from an explicit override or the URL.
func detectRemoteKind(rawurl, override string) remoteKind {
	switch strings.ToLower(strings.TrimSpace(override)) {
	case "github":
		return kindGitHub
	case "gitlab":
		return kindGitLab
	case "gitea":
		return kindGitea
	}
	u := strings.ToLower(rawurl)
	switch {
	case strings.Contains(u, "github.com") || strings.Contains(u, "api.github.com"):
		return kindGitHub
	case strings.Contains(u, "gitlab"):
		return kindGitLab
	default:
		return kindGitea
	}
}

// remoteAPI talks to one provider's REST API.
type remoteAPI struct {
	kind remoteKind
	url  string // base URL, trailing slash trimmed
	key  string
	http *http.Client
}

func newRemoteAPI(cfgURL, key, typ string) *remoteAPI {
	return &remoteAPI{
		kind: detectRemoteKind(cfgURL, typ),
		url:  strings.TrimRight(strings.TrimSpace(cfgURL), "/"),
		key:  strings.TrimSpace(key),
		http: &http.Client{Timeout: 30 * time.Second},
	}
}

// apiRoot returns the REST API root for the provider.
func (r *remoteAPI) apiRoot() string {
	switch r.kind {
	case kindGitHub:
		if r.url == "" || strings.Contains(r.url, "github.com") {
			return "https://api.github.com"
		}
		return r.url + "/api/v3" // GitHub Enterprise
	case kindGitLab:
		return r.url + "/api/v4"
	default: // Gitea
		return r.url + "/api/v1"
	}
}

// authHeader returns the header name/value used to authenticate API calls.
func (r *remoteAPI) authHeader() (string, string) {
	switch r.kind {
	case kindGitLab:
		return "PRIVATE-TOKEN", r.key
	case kindGitHub:
		return "Authorization", "Bearer " + r.key
	default: // Gitea
		return "Authorization", "token " + r.key
	}
}

func (r *remoteAPI) do(method, endpoint string, body any) (int, []byte, error) {
	var rdr io.Reader
	if body != nil {
		b, _ := json.Marshal(body)
		rdr = bytes.NewReader(b)
	}
	req, err := http.NewRequest(method, endpoint, rdr)
	if err != nil {
		return 0, nil, err
	}
	hk, hv := r.authHeader()
	req.Header.Set(hk, hv)
	req.Header.Set("Accept", "application/json")
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	resp, err := r.http.Do(req)
	if err != nil {
		return 0, nil, err
	}
	defer resp.Body.Close()
	data, _ := io.ReadAll(resp.Body)
	return resp.StatusCode, data, nil
}

// authUser returns the login/username of the token owner.
func (r *remoteAPI) authUser() (string, error) {
	code, data, err := r.do("GET", r.apiRoot()+"/user", nil)
	if err != nil {
		return "", err
	}
	if code != 200 {
		return "", fmt.Errorf("authentication failed (HTTP %d): %s", code, firstLine(data))
	}
	var u struct {
		Login    string `json:"login"`    // Gitea, GitHub
		Username string `json:"username"` // GitLab
	}
	json.Unmarshal(data, &u)
	if u.Login != "" {
		return u.Login, nil
	}
	if u.Username != "" {
		return u.Username, nil
	}
	return "", fmt.Errorf("could not determine remote user")
}

// repoExists reports whether owner/repo already exists on the server.
func (r *remoteAPI) repoExists(owner, repo string) (bool, error) {
	var ep string
	if r.kind == kindGitLab {
		ep = r.apiRoot() + "/projects/" + url.PathEscape(owner+"/"+repo)
	} else {
		ep = r.apiRoot() + "/repos/" + owner + "/" + repo
	}
	code, data, err := r.do("GET", ep, nil)
	if err != nil {
		return false, err
	}
	switch code {
	case 200:
		return true, nil
	case 404:
		return false, nil
	default:
		return false, fmt.Errorf("checking repository failed (HTTP %d): %s", code, firstLine(data))
	}
}

// createRepo creates owner/repo on the server with the given visibility and
// (optional) description.
func (r *remoteAPI) createRepo(repo, description string, private bool) error {
	var ep string
	var body map[string]any
	if r.kind == kindGitLab {
		vis := "public"
		if private {
			vis = "private"
		}
		ep = r.apiRoot() + "/projects"
		body = map[string]any{"name": repo, "visibility": vis}
	} else { // Gitea + GitHub
		ep = r.apiRoot() + "/user/repos"
		body = map[string]any{"name": repo, "private": private}
	}
	if description != "" {
		body["description"] = description
	}
	code, data, err := r.do("POST", ep, body)
	if err != nil {
		return err
	}
	if code != 200 && code != 201 {
		return fmt.Errorf("creating repository failed (HTTP %d): %s", code, firstLine(data))
	}
	return nil
}

// repoWebURL returns the https clone/push URL (without credentials).
func (r *remoteAPI) repoWebURL(owner, repo string) string {
	base := r.url
	if r.kind == kindGitHub && (base == "" || strings.Contains(base, "api.github.com")) {
		base = "https://github.com"
	}
	return base + "/" + owner + "/" + repo + ".git"
}

// handlePushRemote implements the `pushremote [description]` command. The
// description, if given, is set on the repository when it is created.
func handlePushRemote(description string) {
	if !requireRepo() {
		return
	}
	if cfg.RemoteURL == "" || cfg.RemoteKey == "" {
		errorln("pushremote needs 'remoteurl' and 'remotekey' in ~/.mgshrc")
		return
	}
	repo := PRJ
	if repo == "" {
		repo = REPO
	}
	if repo == "" {
		errorln("cannot determine repository name")
		return
	}

	private := !strings.EqualFold(strings.TrimSpace(cfg.RemoteVis), "public")

	api := newRemoteAPI(cfg.RemoteURL, cfg.RemoteKey, cfg.RemoteType)

	owner, err := api.authUser()
	if err != nil {
		errorln(err.Error())
		return
	}
	fmt.Printf("%s %s (as %s)\n", col(cGray, "remote"), col(cCyan, api.url), col(cGreen, owner))

	exists, err := api.repoExists(owner, repo)
	if err != nil {
		errorln(err.Error())
		return
	}
	if exists {
		fmt.Printf("repository %s exists\n", col(cGreen, owner+"/"+repo))
	} else {
		vis := "private"
		if !private {
			vis = "public"
		}
		fmt.Printf("creating %s repository %s ...\n", vis, col(cGreen, owner+"/"+repo))
		if err := api.createRepo(repo, description, private); err != nil {
			errorln(err.Error())
			return
		}
	}

	// keep a credential-free remote named "public" for convenience
	web := api.repoWebURL(owner, repo)
	if _, err := gitCapture(DIR, "remote", "get-url", "public"); err == nil {
		gitOK(DIR, "remote", "set-url", "public", web)
	} else {
		gitOK(DIR, "remote", "add", "public", web)
	}

	// authenticate the push with a one-shot Basic auth header so the token is
	// never persisted in the repository's git config
	header := "Authorization: Basic " + base64.StdEncoding.EncodeToString([]byte(owner+":"+api.key))
	if !gitPushHeader(DIR, "public", header, "--all") {
		return
	}
	gitPushHeader(DIR, "public", header, "--tags")
	fmt.Println(col(cGreen, "pushed to ") + col(cCyan, web))
}

// gitPushHeader runs `git push <remote> <args...>` with an extra HTTP auth
// header, disabling interactive credential prompts.
func gitPushHeader(dir, remote, header string, args ...string) bool {
	full := append([]string{"-c", "http.extraHeader=" + header, "push", remote}, args...)
	c := exec.Command("git", full...)
	c.Dir = dir
	c.Stdin = os.Stdin
	c.Stdout = os.Stdout
	c.Stderr = os.Stderr
	c.Env = append(os.Environ(), "GIT_TERMINAL_PROMPT=0")
	if err := c.Run(); err != nil {
		errorln("git push " + remote + " " + strings.Join(args, " ") + " failed")
		return false
	}
	return true
}

// firstLine trims an API response body to a short single-line summary.
func firstLine(b []byte) string {
	s := strings.TrimSpace(string(b))
	if i := strings.IndexByte(s, '\n'); i >= 0 {
		s = s[:i]
	}
	if len(s) > 200 {
		s = s[:200]
	}
	return s
}