package worker

import (
	"context"
	"database/sql"
	"fmt"
	"io"
	"net/url"
	"os"
	"sort"
	"strings"
	"sync"
	"time"

	"github.com/go-git/go-git/v5"
	"github.com/go-git/go-git/v5/plumbing/filemode"
	"github.com/go-git/go-git/v5/plumbing/object"
	"github.com/go-git/go-git/v5/storage/memory"
	"github.com/pkg/errors"
	"go.unistack.org/micro/v3/logger"
	"go.unistack.org/pkgdash/internal/models"
	"go.unistack.org/pkgdash/internal/modules"
	"go.unistack.org/pkgdash/internal/storage"
	"golang.org/x/mod/modfile"
	"golang.org/x/mod/module"
)

func Run(ctx context.Context, log logger.Logger, store storage.Storage, td time.Duration) {
	modTicker := time.NewTicker(5 * time.Second)
	defer modTicker.Stop()
	pkgTicker := time.NewTicker(5 * time.Second)
	defer pkgTicker.Stop()

	var wg sync.WaitGroup
	for {
		select {
		case <-ctx.Done():
			return
		case <-pkgTicker.C:
			packages, err := store.PackagesProcess(ctx, td)
			if err != nil {
				if err != sql.ErrNoRows {
					continue
				}
				log.Fatal(ctx, "failed to get packages to process: %v", err)
			}
			wg.Add(len(packages))
			for _, pkg := range packages {
				go func(p *models.Package) {
					if err := parseModFile(ctx, log, store, p); err != nil {
						log.Error(ctx, "failed to process package %s: %v", p.Name, err)
					}
					p.LastCheck.Time = time.Now()
					wg.Done()
				}(pkg)
			}
			wg.Wait()
			if err = store.PackagesUpdateLastCheck(ctx, packages); err != nil {
				log.Error(ctx, "update packages last_check %#+v, err: %v", packages, err)
			}
		case <-modTicker.C:
			modules, err := store.ModulesProcess(ctx, td)
			if err != nil {
				if err != sql.ErrNoRows {
					continue
				}
				log.Fatal(ctx, "failed to get modules to process: %v", err)
			}
			if err := processModules(ctx, log, store, modules); err != nil {
				log.Error(ctx, "failed to process modules: %v", err)
			}
		}
	}
}

func parseModFile(ctx context.Context, log logger.Logger, store storage.Storage, pkg *models.Package) error {
	log.Info(ctx, "process package %v", pkg)

	u, err := url.Parse(pkg.URL)
	if err != nil {
		return err
	}

	var rev string
	if idx := strings.Index(u.Path, "@"); idx > 0 {
		rev = u.Path[idx+1:]
	}

	cloneOpts := &git.CloneOptions{
		URL:      pkg.URL,
		Progress: os.Stdout,
	}

	if len(rev) == 0 {
		cloneOpts.SingleBranch = true
		cloneOpts.Depth = 1
	}

	if err = cloneOpts.Validate(); err != nil {
		return err
	}

	repo, err := git.CloneContext(ctx, memory.NewStorage(), nil, cloneOpts)
	if err != nil {
		return err
	}

	ref, err := repo.Head()
	if err != nil {
		return fmt.Errorf("failed to get head: %v", err)
	}

	commit, err := repo.CommitObject(ref.Hash())
	if err != nil {
		return fmt.Errorf("failed to get commit: %v", err)
	}

	tree, err := commit.Tree()
	if err != nil {
		return err
	}

	unique := make(map[string]*models.Module)
	var mvs []module.Version
	err = tree.Files().ForEach(func(file *object.File) error {
		if file == nil {
			err = errors.New("file pointer is nil")
			log.Error(ctx, "file tree error", err)
			return err
		}

		switch file.Mode {
		case filemode.Regular:
			if strings.HasSuffix(file.Name, "go.mod") {
				if mvs, err = parseFile(file); err != nil {
					return err
				}
				for i := range mvs {
					unique[mvs[i].Path] = &models.Module{
						Name:    mvs[i].Path,
						Version: mvs[i].Version,
					}
				}
			}
		}
		return nil
	})

	modules := make([]*models.Module, 0, len(unique))
	for _, v := range unique {
		modules = append(modules, v)
	}

	sort.Slice(modules, func(i, j int) bool {
		return modules[i].Name < modules[j].Name
	})

	if err = store.PackageModulesCreate(ctx, pkg, modules); err != nil {
		log.Error(ctx, "failed to set create modules: %v", err)
		return err
	}

	return nil
}

func processModules(ctx context.Context, log logger.Logger, store storage.Storage, mods []*models.Module) error {
	mvs := make(map[string]*models.Module, len(mods))

	for _, mod := range mods {
		mvs[mod.Name] = mod
	}

	mvsu := make([]module.Version, 0, len(mvs))
	for _, mv := range mvs {
		mvsu = append(mvsu, module.Version{Path: mv.Name, Version: mv.Version})
	}

	modules.Updates(modules.UpdateOptions{
		Pre:     false,
		Major:   false,
		Cached:  false,
		Modules: mvsu,
		OnUpdate: func(u modules.Update) {
			if u.Err != nil {
				log.Error(ctx, "%s: failed: %v", u.Module.Path, u.Err)
			} else {
				mvs[u.Module.Path].Version = u.Version
			}
		},
	})

	if err := store.ModuleCreate(ctx, mods); err != nil {
		return err
	}

	return nil
}

func parseFile(file *object.File) ([]module.Version, error) {
	r, err := file.Reader()
	if err != nil {
		return nil, err
	}

	data, err := io.ReadAll(r)
	r.Close()
	if err != nil {
		return nil, err
	}

	modfile, err := modfile.ParseLax("go.mod", data, nil)
	if err != nil {
		return nil, err
	}

	mods := make([]module.Version, 0, len(modfile.Require))
	for _, req := range modfile.Require {
		mods = append(mods, req.Mod)
	}

	sort.Slice(mods, func(i, j int) bool {
		return mods[i].Path < mods[j].Path
	})

	return mods, nil
}