package bulk

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	"tangled.org/odd.computer/isomorph/internal/fetch"
	"tangled.org/odd.computer/isomorph/internal/repourl"
)

const (
	defaultGitHubAPI = "https://api.github.com"
	githubAccept     = "application/vnd.github+json"
	// githubTTL is how long a repository lookup is cached. Renames are rare and GitHub keeps
	// redirecting the old name for as long as it is unclaimed, so a stale answer is harmless.
	githubTTL = 30 * 24 * time.Hour
)

// githubAPI overrides the GitHub REST base URL; tests point it at an httptest server. Empty
// means defaultGitHubAPI.
var githubAPI string

// LookupGitHub resolves a github.com key through the repositories API, which follows renames
// and ownership transfers: the key derived from the response's full_name is the current one.
// gone is true (with key returned unchanged) when the API answers 404, the repository no longer
// exists. Rate limits, offline mode and network failures are returned as errors. Keys on other
// hosts are returned as is.
func LookupGitHub(ctx context.Context, client *fetch.Client, key string) (canonical string, gone bool, err error) {
	if !strings.HasPrefix(key, "github.com/") {
		return key, false, nil
	}
	c, err := repourl.Parse("https://" + key)
	if err != nil || c.Host != "github.com" || c.Kind != repourl.KindRepo {
		return key, false, nil
	}
	if client == nil {
		return key, false, errors.New("bulk: rename lookup needs a fetch.Client")
	}
	api := githubAPI
	if api == "" {
		api = defaultGitHubAPI
	}
	var resp struct {
		FullName string `json:"full_name"`
	}
	u := api + "/repos/" + c.Path
	err = client.GetJSON(ctx, u, &resp, fetch.WithHeader("Accept", githubAccept), fetch.WithTTL(githubTTL))
	if fetch.IsNotFound(err) {
		return key, true, nil
	}
	if err != nil {
		return key, false, fmt.Errorf("bulk: %s: rename lookup: %w", key, err)
	}
	if resp.FullName == "" {
		return key, false, fmt.Errorf("bulk: %s: rename lookup: response has no full_name", key)
	}
	return "github.com/" + strings.ToLower(resp.FullName), false, nil
}