package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"strings"
	"time"
)

// The forge as this bundle reaches it: its own HTTP interface on the machine, as the forge's admin
// account, which the vault delivered into a file this module owns (novox/hq ADR 0086). Basic
// authentication, so this bundle mints nothing and keeps nothing: the TypeScript bundle's token is its
// own. The password is read when a call is made and never logged, answered or put in an error.

// Forge is the forge's HTTP interface.
type Forge struct {
	URL          string // e.g. http://127.0.0.1:3000
	User         string
	PasswordFile string
	Owner        string // the package registry's owner, as the seat serves it
	HTTP         *http.Client
}

// ForgeFromEnv is the forge as the manifest hands it to this bundle.
func ForgeFromEnv() (*Forge, error) {
	f := &Forge{
		URL:          strings.TrimRight(os.Getenv("MESH_GITEA_URL"), "/"),
		User:         os.Getenv("MESH_GITEA_ADMIN_USER"),
		PasswordFile: os.Getenv("MESH_GITEA_ADMIN_PASSWORD_FILE"),
		Owner:        os.Getenv("MESH_NPM_OWNER"),
	}
	var missing []string
	for name, v := range map[string]string{"MESH_GITEA_URL": f.URL, "MESH_GITEA_ADMIN_USER": f.User,
		"MESH_GITEA_ADMIN_PASSWORD_FILE": f.PasswordFile, "MESH_NPM_OWNER": f.Owner} {
		if v == "" {
			missing = append(missing, name)
		}
	}
	if len(missing) > 0 {
		return nil, fmt.Errorf("the forge cannot be reached: %s not set by the manifest", strings.Join(missing, ", "))
	}
	return f, nil
}

// errNotFound is the forge answering 404.
var errNotFound = errors.New("not found")

// statusError is an answer the forge gave that is not a success, said without the request's credential.
type statusError struct {
	method, path string
	status       int
	said         string
}

func (e *statusError) Error() string {
	return fmt.Sprintf("the forge answered %d to %s %s: %s", e.status, e.method, e.path, e.said)
}

func (f *Forge) client() *http.Client {
	if f.HTTP != nil {
		return f.HTTP
	}
	return &http.Client{Timeout: 20 * time.Second}
}

func (f *Forge) password() (string, error) {
	raw, err := os.ReadFile(f.PasswordFile)
	if err != nil {
		// The path is the manifest's, not a secret; the content never appears.
		return "", fmt.Errorf("the forge's admin password cannot be read from its file: %w", err)
	}
	return strings.TrimSpace(string(raw)), nil
}

// do sends one request and answers the body; 404 is errNotFound.
func (f *Forge) do(ctx context.Context, method, path string) ([]byte, error) {
	password, err := f.password()
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequestWithContext(ctx, method, f.URL+path, nil)
	if err != nil {
		return nil, err
	}
	req.SetBasicAuth(f.User, password)
	req.Header.Set("Accept", "application/json")
	res, err := f.client().Do(req)
	if err != nil {
		return nil, fmt.Errorf("the forge did not answer %s %s: %w", method, path, err)
	}
	defer res.Body.Close()
	body, err := io.ReadAll(io.LimitReader(res.Body, 32<<20))
	if err != nil {
		return nil, err
	}
	switch {
	case res.StatusCode == http.StatusNotFound:
		return nil, fmt.Errorf("%s %s: %w", method, path, errNotFound)
	case res.StatusCode >= 300:
		said := strings.TrimSpace(string(body))
		if len(said) > 300 {
			said = said[:300] + "…"
		}
		return nil, &statusError{method, path, res.StatusCode, said}
	}
	return body, nil
}

func (f *Forge) getJSON(ctx context.Context, path string, into any) error {
	body, err := f.do(ctx, http.MethodGet, path)
	if err != nil {
		return err
	}
	if err := json.Unmarshal(body, into); err != nil {
		return fmt.Errorf("the forge's answer to %s is not readable: %w", path, err)
	}
	return nil
}

// PackageVersion is one version of one package, as the forge lists it.
type PackageVersion struct {
	Name      string    `json:"name"`
	Version   string    `json:"version"`
	CreatedAt time.Time `json:"created_at"`
}

const pageSize = 50

// Packages is every npm package version of the owner, all pages.
func (f *Forge) Packages(ctx context.Context) ([]PackageVersion, error) {
	var all []PackageVersion
	for page := 1; page <= 1000; page++ {
		var batch []PackageVersion
		path := fmt.Sprintf("/api/v1/packages/%s?type=npm&page=%d&limit=%d", url.PathEscape(f.Owner), page, pageSize)
		if err := f.getJSON(ctx, path, &batch); err != nil {
			return nil, err
		}
		all = append(all, batch...)
		if len(batch) < pageSize {
			return all, nil
		}
	}
	return nil, errors.New("the forge listed more than 1000 pages of packages; stopped rather than read for ever")
}

func (f *Forge) versionPath(name, version string) string {
	return fmt.Sprintf("/api/v1/packages/%s/npm/%s/%s", url.PathEscape(f.Owner), url.PathEscape(name), url.PathEscape(version))
}

// Size is the bytes of one version's files.
func (f *Forge) Size(ctx context.Context, name, version string) (int64, error) {
	var files []struct {
		Size int64 `json:"size"`
	}
	if err := f.getJSON(ctx, f.versionPath(name, version)+"/files", &files); err != nil {
		return 0, err
	}
	var total int64
	for _, file := range files {
		total += file.Size
	}
	return total, nil
}

// DistTags is the dist-tags of one package, from the registry's own metadata.
func (f *Forge) DistTags(ctx context.Context, name string) (map[string]string, error) {
	var meta struct {
		DistTags map[string]string `json:"dist-tags"`
	}
	path := fmt.Sprintf("/api/packages/%s/npm/%s", url.PathEscape(f.Owner), url.PathEscape(name))
	if err := f.getJSON(ctx, path, &meta); err != nil {
		return nil, err
	}
	return meta.DistTags, nil
}

// Delete removes one version from the registry.
func (f *Forge) Delete(ctx context.Context, name, version string) error {
	_, err := f.do(ctx, http.MethodDelete, f.versionPath(name, version))
	return err
}

// Repository is one repository on the forge, as far as reading its manifests needs.
type Repository struct {
	FullName      string `json:"full_name"`
	DefaultBranch string `json:"default_branch"`
	Empty         bool   `json:"empty"`
}

// Repositories is every repository the admin sees.
func (f *Forge) Repositories(ctx context.Context) ([]Repository, error) {
	var all []Repository
	for page := 1; page <= 1000; page++ {
		var found struct {
			Data []Repository `json:"data"`
		}
		if err := f.getJSON(ctx, fmt.Sprintf("/api/v1/repos/search?page=%d&limit=%d", page, pageSize), &found); err != nil {
			return nil, err
		}
		all = append(all, found.Data...)
		if len(found.Data) < pageSize {
			return all, nil
		}
	}
	return nil, errors.New("the forge listed more than 1000 pages of repositories; stopped rather than read for ever")
}

func repoPath(fullName string) string {
	owner, name, _ := strings.Cut(fullName, "/")
	return url.PathEscape(owner) + "/" + url.PathEscape(name)
}

// Files is every file path on a branch, all pages of the forge's tree.
func (f *Forge) Files(ctx context.Context, repo Repository) ([]string, error) {
	var paths []string
	seen := 0
	for page := 1; page <= 1000; page++ {
		var tree struct {
			Tree []struct {
				Path string `json:"path"`
				Type string `json:"type"`
			} `json:"tree"`
			Truncated  bool `json:"truncated"`
			TotalCount int  `json:"total_count"`
		}
		path := fmt.Sprintf("/api/v1/repos/%s/git/trees/%s?recursive=true&page=%d&per_page=1000",
			repoPath(repo.FullName), url.PathEscape(repo.DefaultBranch), page)
		if err := f.getJSON(ctx, path, &tree); err != nil {
			return nil, err
		}
		for _, e := range tree.Tree {
			if e.Type == "blob" {
				paths = append(paths, e.Path)
			}
		}
		seen += len(tree.Tree)
		if len(tree.Tree) == 0 || !tree.Truncated && (tree.TotalCount == 0 || seen >= tree.TotalCount) {
			return paths, nil
		}
	}
	return nil, fmt.Errorf("%s has more than 1000 pages of files; not read whole", repo.FullName)
}

// Raw is one file's content on the repository's default branch.
func (f *Forge) Raw(ctx context.Context, repo Repository, file string) ([]byte, error) {
	escaped := strings.Split(file, "/")
	for i := range escaped {
		escaped[i] = url.PathEscape(escaped[i])
	}
	return f.do(ctx, http.MethodGet, fmt.Sprintf("/api/v1/repos/%s/raw/%s?ref=%s",
		repoPath(repo.FullName), strings.Join(escaped, "/"), url.QueryEscape(repo.DefaultBranch)))
}