package main

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"text/template"
	"time"

	"git.unistack.org/unistack-org/pkgdash/internal/modules"
	"github.com/go-git/go-git/v5"
	gitconfig "github.com/go-git/go-git/v5/config"
	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/object"
	httpauth "github.com/go-git/go-git/v5/plumbing/transport/http"
	yamlcodec "go.unistack.org/micro-codec-yaml/v4"
	envconfig "go.unistack.org/micro-config-env/v4"
	fileconfig "go.unistack.org/micro-config-file/v4"
	"go.unistack.org/micro/v4/config"
	"go.unistack.org/micro/v4/logger"
	"go.unistack.org/micro/v4/options"
	"golang.org/x/mod/modfile"
)

// https://docs.github.com/ru/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file

var (
	DefaultPullRequestTitle = `Bump {{.Name}} from {{.VersionOld}} to {{.VersionNew}}`
	DefaultPullRequestBody  = `Bumps {{.Name}} from {{.VersionOld}} to {{.VersionNew}}`
)

type Config struct {
	PullRequestTitle string `json:"pull_request_title" yaml:"pull_request_title"`
	PullRequestBody  string `json:"pull_request_body" yaml:"pull_request_body"`
}

var (
	configFiles = []string{
		"dependabot.yml",
		"pkgdash.yml",
		"pkgdash.yaml",
	}
	configDirs = []string{
		".gitea",
		".github",
		".gitlab",
	}
	repoMgmt = map[string]string{
		".gitea":  "gitea",
		".gogs":   "gogs",
		".github": "github",
		".gitlab": "gitlab",
	}
)

type Data struct {
	Modules map[string]modules.Update
}

func main() {
	var err error

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	cfg := &Config{}

	if err = config.Load(ctx,
		[]config.Config{
			config.NewConfig(
				config.Struct(cfg),
			),

			envconfig.NewConfig(
				config.Struct(cfg),
			),
		},
		config.LoadOverride(true),
	); err != nil {
		logger.Fatalf(ctx, "failed to load config: %v", err)
	}

	for _, configDir := range configDirs {
		for _, configFile := range configFiles {
			c := fileconfig.NewConfig(
				config.AllowFail(true),
				config.Struct(cfg),
				options.Codec(yamlcodec.NewCodec()),
				fileconfig.Path(filepath.Join(configDir, configFile)),
			)
			if err = c.Load(ctx, config.LoadOverride(true)); err != nil {
				logger.Fatalf(ctx, "failed to load config: %v", err)
			}
		}
	}

	if cfg.PullRequestBody == "" {
		cfg.PullRequestBody = DefaultPullRequestBody
	}

	if cfg.PullRequestTitle == "" {
		cfg.PullRequestTitle = DefaultPullRequestTitle
	}

	path := "."
	if len(os.Args) > 1 {
		path = os.Args[1]
	}

	name, err := modules.FindModFile(path)
	if err != nil {
		panic(err)
	}
	buf, err := os.ReadFile(name)
	if err != nil {
		panic(err)
	}
	mfile, err := modfile.Parse(name, buf, nil)
	if err != nil {
		panic(err)
	}

	mvs := make(map[string]modules.Update)

	updateOptions := modules.UpdateOptions{
		Pre:    false,
		Major:  false,
		Cached: true,
		OnUpdate: func(u modules.Update) {
			if u.Err != nil {
				logger.Errorf(ctx, "%s: failed: %v", u.Module.Path, u.Err)
				return
			}
			mvs[u.Module.Path] = u
		},
	}

	for _, req := range mfile.Require {
		updateOptions.Modules = append(updateOptions.Modules, req.Mod)
	}

	modules.Updates(updateOptions)

	repoMgmt := getRepoMgmt()
	if repoMgmt == "unknown" {
		logger.Fatalf(ctx, "failed to get repo management")
	}

	branch := os.Getenv("GITHUB_REF_NAME")
	switch repoMgmt {
	case "gitea":
		err = giteaPullRequest(ctx, cfg, branch, mvs)
	}

	if err != nil {
		logger.Fatalf(ctx, "failed to create pr: %v", err)
	}
}

func getRepoMgmt() string {
	wd, err := os.Getwd()
	if err != nil {
		return "unknown"
	}

	p := filepath.Clean(wd)
	for {
		for _, configDir := range configDirs {
			_, err := os.Stat(filepath.Join(p, configDir))
			if name, ok := repoMgmt[configDir]; ok && err == nil {
				return name
			}
		}
		if p == "/" {
			return "unknown"
		}
		p = filepath.Clean(filepath.Join(p, ".."))
	}
}

func giteaPullRequest(ctx context.Context, cfg *Config, branch string, mods map[string]modules.Update) error {
	envAPIURL := os.Getenv("GITHUB_API_URL")
	envREPOSITORY := os.Getenv("GITHUB_REPOSITORY")
	envTOKEN := os.Getenv("GITHUB_TOKEN")

	var buf []byte
	var err error

	tplTitle, err := template.New("pull_request_title").Parse(cfg.PullRequestTitle)
	if err != nil {
		logger.Fatalf(ctx, "failed to parse template: %v", err)
	}

	wTitle := bytes.NewBuffer(nil)

	tplBody, err := template.New("pull_request_body").Parse(cfg.PullRequestBody)
	if err != nil {
		logger.Fatalf(ctx, "failed to parse template: %v", err)
	}

	wBody := bytes.NewBuffer(nil)

	repo, err := git.PlainOpenWithOptions(".", &git.PlainOpenOptions{DetectDotGit: true})
	if err != nil {
		logger.Fatalf(ctx, "failed to open repo: %v", err)
	}

	headRef, err := repo.Head()
	if err != nil {
		logger.Fatalf(ctx, "failed to get repo head: %v", err)
	}

	wtree, err := repo.Worktree()
	if err != nil {
		logger.Fatalf(ctx, "failed to get worktree: %v", err)
	}

	type giteaPull struct {
		URL   string `json:"url"`
		Title string `json:"title"`
		Base  struct {
			Ref string `json:"ref"`
		} `json:"base"`
		ID int64 `json:"id"`
	}

	var pulls []*giteaPull
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, envAPIURL+"/repos/"+envREPOSITORY+"/pulls?state=open&token="+envTOKEN, nil)
	if err != nil {
		return err
	}
	req.Header.Add("Accept", "application/json")
	req.Header.Add("Content-Type", "application/json")

	rsp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}

	buf, _ = io.ReadAll(rsp.Body)
	if rsp.StatusCode != http.StatusOK {
		return fmt.Errorf("unknown error: %s", buf)
	}

	if err = json.Unmarshal(buf, &pulls); err != nil {
		logger.Fatalf(ctx, "failed to decode response %s err: %v", buf, err)
	}

	for path := range mods {
		for _, pull := range pulls {
			if strings.Contains(pull.Title, path) && pull.Base.Ref == branch {
				logger.Infof(ctx, "skip %s as pr already exists %s", path, pull.URL)
				delete(mods, path)
			}
		}
	}

	for path, mod := range mods {
		wTitle.Reset()
		wBody.Reset()

		logger.Infof(ctx, "update %s from %s to %s", path, mod.Module.Version, mod.Version)

		logger.Infof(ctx, "reset worktree")
		if err = wtree.Reset(&git.ResetOptions{Mode: git.HardReset}); err != nil {
			logger.Fatalf(ctx, "failed to reset repo branch: %v", err)
		}

		logger.Infof(ctx, "checkout ref %s", headRef)
		if err = wtree.Checkout(&git.CheckoutOptions{
			Hash:   headRef.Hash(),
			Create: false,
			Force:  true,
		}); err != nil {
			logger.Fatalf(ctx, "failed to get checkout tree: %v", err)
		}

		epath, err := exec.LookPath("go")
		if errors.Is(err, exec.ErrDot) {
			err = nil
		}
		if err != nil {
			logger.Fatalf(ctx, "failed to find go command: %v", err)
		}

		var cmd *exec.Cmd
		var out []byte

		cmd = exec.CommandContext(ctx, epath, "mod", "edit", fmt.Sprintf("-require=%s@%s", path, mod.Version))
		if out, err = cmd.CombinedOutput(); err != nil {
			logger.Fatalf(ctx, "failed to run go mod edit: %s err: %v", out, err)
		}

		cmd = exec.CommandContext(ctx, epath, "mod", "tidy")
		if out, err = cmd.CombinedOutput(); err != nil {
			logger.Fatalf(ctx, "failed to run go mod tidy: %s err: %v", out, err)
		}

		logger.Infof(ctx, "worktree add go.mod")
		if _, err = wtree.Add("go.mod"); err != nil {
			logger.Fatalf(ctx, "failed to add file: %v", err)
		}

		logger.Infof(ctx, "worktree add go.sum")
		if _, err = wtree.Add("go.sum"); err != nil {
			logger.Fatalf(ctx, "failed to add file: %v", err)
		}

		logger.Infof(ctx, "worktree commit")
		commit, err := wtree.Commit(wTitle.String(), &git.CommitOptions{
			Author: &object.Signature{
				Name:  "gitea-actions",
				Email: "info@unistack.org",
				When:  time.Now(),
			},
		})
		if err != nil {
			logger.Fatalf(ctx, "failed to commit: %v", err)
		}

		newref := plumbing.NewHashReference(plumbing.ReferenceName(fmt.Sprintf("refs/heads/pkgdash/go_modules/%s-%s", path, mod.Version)), commit)

		if err = repo.Storer.SetReference(newref); err != nil {
			logger.Fatalf(ctx, "failed to create repo branch: %v", err)
		}

		refspec := gitconfig.RefSpec(fmt.Sprintf("+" + newref.Name().String() + ":" + newref.Name().String()))
		logger.Infof(ctx, "try to push %s", refspec)

		if err = repo.PushContext(ctx, &git.PushOptions{
			RefSpecs: []gitconfig.RefSpec{refspec},
			Auth:     &httpauth.BasicAuth{Username: envTOKEN, Password: envTOKEN},
			Force:    true,
		}); err != nil {
			logger.Fatalf(ctx, "failed to push repo branch: %v", err)
		}

		data := map[string]string{
			"Name":       path,
			"VersionOld": mod.Module.Version,
			"VersionNew": mod.Version,
		}

		if err = tplTitle.Execute(wTitle, data); err != nil {
			logger.Fatalf(ctx, "failed to execute template: %v", err)
		}
		if err = tplBody.Execute(wBody, data); err != nil {
			logger.Fatalf(ctx, "failed to execute template: %v", err)
		}

		body := map[string]string{
			"base":  branch,
			"body":  wBody.String(),
			"head":  fmt.Sprintf("pkgdash/go_modules/%s-%s", path, mod.Version),
			"title": wTitle.String(),
		}
		logger.Infof(ctx, "raw body: %#+v", body)

		buf, err = json.Marshal(body)
		if err != nil {
			return err
		}

		logger.Infof(ctx, "marshal body: %s", buf)

		req, err := http.NewRequestWithContext(ctx, http.MethodPost, envAPIURL+"/repos/"+envREPOSITORY+"/pulls?token="+envTOKEN, bytes.NewReader(buf))
		if err != nil {
			return err
		}
		req.Header.Add("Accept", "application/json")
		req.Header.Add("Content-Type", "application/json")

		rsp, err := http.DefaultClient.Do(req)
		if err != nil {
			return err
		}
		if rsp.StatusCode != http.StatusCreated {
			buf, _ = io.ReadAll(rsp.Body)
			return fmt.Errorf("unknown error: %s", buf)
		}

	}

	return nil
}