// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package app

import (
	"cmp"
	"context"
	"errors"
	"fmt"
	"maps"
	"slices"
	"strconv"
	"strings"

	"gitea.dev/tea/internal/auth"
	"gitea.dev/tea/internal/clierr"
	"gitea.dev/tea/internal/git"
	"gitea.dev/tea/internal/services"
	"gitea.dev/tea/internal/settings"
	"gitea.dev/tea/internal/transport"
)

type target struct {
	Host       string `json:"host"`
	User       string `json:"user"`
	Repo       string `json:"repo"`
	HostSource string `json:"host_source"`
	UserSource string `json:"user_source"`
	RepoSource string `json:"repo_source"`
	client     *transport.Client
	// host holds the selected instance's settings with the GITEA_TOKEN environment overrides applied.
	host settings.Host
	// gitProtocol is the instance's git_protocol, else the git_protocol preference.
	gitProtocol string
}

var errRepositoryRequired = errors.New("repository required: use --repo owner/name")

func (a *application) resolve(ctx context.Context, requireRepo bool) (target, error) {
	return a.resolveTarget(ctx, requireRepo, true)
}

// tokenInstance returns the instance a GITEA_TOKEN belongs to: GITEA_INSTANCE_URL, else TEA_HOST.
func (a *application) tokenInstance() string {
	if instance := a.deps.Getenv("GITEA_INSTANCE_URL"); instance != "" {
		return instance
	}
	return a.deps.Getenv("TEA_HOST")
}

// environmentHosts applies GITEA_INSTANCE_INSECURE and GITEA_INSTANCE_SSH_HOST to the instance
// of a GITEA_TOKEN login, without persisting them.
func (a *application) environmentHosts(hosts map[string]settings.Host) (map[string]settings.Host, error) {
	insecure, sshHost := a.deps.Getenv("GITEA_INSTANCE_INSECURE"), a.deps.Getenv("GITEA_INSTANCE_SSH_HOST")
	if a.deps.Getenv("GITEA_TOKEN") == "" || (insecure == "" && sshHost == "") {
		return hosts, nil
	}
	instance, err := settings.ResolveHost(a.tokenInstance(), hosts)
	if err != nil {
		return hosts, nil // The token's instance check reports this.
	}
	host := hosts[instance]
	if insecure != "" {
		if host.Insecure, err = strconv.ParseBool(insecure); err != nil {
			return nil, clierr.Wrap(clierr.Usage, errors.New("GITEA_INSTANCE_INSECURE must be true or false"))
		}
	}
	if sshHost != "" {
		if _, err := settings.SSHEndpoint(sshHost); err != nil {
			return nil, clierr.Wrap(clierr.Usage, fmt.Errorf("invalid GITEA_INSTANCE_SSH_HOST: %w", err))
		}
		host.SSHHost = sshHost
	}
	result := maps.Clone(hosts)
	if result == nil {
		result = map[string]settings.Host{}
	}
	result[instance] = host
	return result, nil
}

// targetRequest says what a command needs resolved.
type targetRequest struct {
	requireRepo, authenticate bool
	// repo names the repository a command argument selected, such as the repository of an
	// issue URL; it takes precedence over discovery and must agree with --repo.
	repo, repoSource string
}

func (a *application) resolveTarget(ctx context.Context, requireRepo, authenticate bool) (target, error) {
	return a.resolveRequest(ctx, targetRequest{requireRepo: requireRepo, authenticate: authenticate})
}

func (a *application) resolveRequest(ctx context.Context, req targetRequest) (target, error) {
	t, err := a.connect(ctx, req)
	if err != nil {
		return t, err
	}
	// A bare repository NAME belongs to the account tea acts as, which is known only now.
	if t.Repo != "" && !strings.Contains(t.Repo, "/") {
		owner := cmp.Or(a.options.sudo, t.User)
		if owner == "" {
			return t, clierr.Wrap(clierr.Usage, fmt.Errorf("cannot tell who owns repository %q; use OWNER/%s", t.Repo, t.Repo))
		}
		t.Repo = owner + "/" + t.Repo
	}
	return t, nil
}

// connect selects the instance, account and repository and builds the authenticated client.
func (a *application) connect(ctx context.Context, req targetRequest) (target, error) {
	s, err := a.deps.Settings.Load()
	if err != nil {
		return target{}, err
	}
	if s.Hosts.Hosts, err = a.environmentHosts(s.Hosts.Hosts); err != nil {
		return target{}, err
	}
	t := target{}
	rawRepo, err := a.repositorySource(ctx, &t, s, req)
	if err != nil {
		return t, err
	}
	if rawRepo != "" {
		if err := a.selectRepository(ctx, &t, s, rawRepo); err != nil {
			return t, err
		}
	}
	if err := a.selectHost(&t, s); err != nil {
		return t, err
	}
	host := s.Hosts.Hosts[t.Host]
	t.host = host
	t.gitProtocol = cmp.Or(host.GitProtocol, s.Preferences.GitProtocol)
	if err := a.selectAccount(ctx, &t, s, req.authenticate); err != nil {
		return t, err
	}
	if !req.authenticate {
		return t, nil
	}
	token := a.deps.Getenv("GITEA_TOKEN")
	environmentCredential := token != ""
	if token != "" {
		normalized, err := settings.ResolveHost(a.tokenInstance(), s.Hosts.Hosts)
		if err != nil || normalized != t.Host {
			return t, clierr.Wrap(clierr.Authentication, errors.New("GITEA_TOKEN requires GITEA_INSTANCE_URL or TEA_HOST matching the selected instance"))
		}
	} else {
		account, exists := host.Users[t.User]
		if !exists {
			return t, clierr.Wrap(clierr.Authentication, t.accountError(t.User))
		}
		if account.Tokenless() {
			signer, err := auth.SignerForAccount(account, a.sshPassphrase(ctx, a.policy(s), account.SSHKey))
			if err != nil {
				return t, clierr.Wrap(clierr.Authentication, err)
			}
			client := a.deps.Client(t.Host, "", host.Insecure)
			client.Signer, client.Sudo = signer, a.options.sudo
			t.client = client
			return t, nil
		}
		credential, err := a.deps.Credentials.Load(t.Host, t.User, account.CredentialStore)
		if err != nil {
			return t, clierr.Wrap(clierr.Authentication, err)
		}
		if account.AuthMethod == settings.AuthOAuth {
			manager, err := auth.NewManager(a.deps.Settings, a.deps.Credentials)
			if err != nil {
				return t, err
			}
			credential, err = manager.Refresh(ctx, t.Host, t.User, a.deps.Client(t.Host, "", host.Insecure).HTTP, false, a.deps.Now())
			if err != nil {
				return t, clierr.Wrap(clierr.Authentication, err)
			}
		}
		token = credential.AccessToken
	}
	t.client = a.deps.Client(t.Host, token, host.Insecure)
	if environmentCredential {
		actual, err := services.CurrentAccount(ctx, t.client)
		if err != nil {
			return t, err
		}
		// The message must not reveal which account the token belongs to.
		if !services.MatchAccount(t.User, actual) {
			return t, clierr.Wrap(clierr.Authentication, errors.New("GITEA_TOKEN does not belong to the selected account; supply its matching --user or remove the environment token to use stored credentials"))
		}
		if t.User == "" {
			t.UserSource = "GITEA_TOKEN authenticated account"
		}
		t.User = actual
	}
	// Set after the environment-token identity check, which must see the authenticated account.
	t.client.Sudo = a.options.sudo
	return t, nil
}

// repositorySource returns the raw repository the command targets and records its source: an
// argument's repository, --repo, TEA_REPO, the saved tea.repository, or a discovered Git remote.
func (a *application) repositorySource(ctx context.Context, t *target, s settings.Snapshot, req targetRequest) (string, error) {
	if req.repo != "" {
		if err := a.agreesWithRepoFlag(req, s.Hosts.Hosts); err != nil {
			return "", err
		}
		t.RepoSource = req.repoSource
		return req.repo, nil
	}
	if a.options.repo != "" {
		t.RepoSource = "--repo"
		return a.options.repo, nil
	}
	if raw := a.deps.Getenv("TEA_REPO"); raw != "" {
		t.RepoSource = "TEA_REPO"
		return raw, nil
	}
	if !req.requireRepo {
		return "", nil
	}
	// Discovery probes fail outside a checkout; Git's diagnostics would only precede tea's own error.
	probe := func(args ...string) (string, error) { return a.gitProbe().Output(ctx, a.options.cwd, false, args...) }
	if saved, err := probe("config", "--get", "tea.repository"); err == nil && saved != "" {
		t.RepoSource = "git config tea.repository"
		return saved, nil
	}
	remote := cmp.Or(a.options.remote, s.Preferences.Remote)
	remote, err := git.DiscoverRemote(ctx, a.gitProbe(), a.options.cwd, remote)
	if errors.Is(err, git.ErrAmbiguousRemote) {
		return "", clierr.Wrap(clierr.Usage, err)
	}
	if err != nil {
		return "", clierr.Wrap(clierr.Usage, errRepositoryRequired)
	}
	raw, err := probe("remote", "get-url", remote)
	if err != nil {
		return "", fmt.Errorf("cannot read the URL of Git remote %q: %w", remote, err)
	}
	t.RepoSource = "remote " + remote
	return raw, nil
}

// agreesWithRepoFlag rejects an argument naming another repository than --repo.
func (a *application) agreesWithRepoFlag(req targetRequest, hosts map[string]settings.Host) error {
	if a.options.repo == "" {
		return nil
	}
	selected, selectedErr := settings.ParseRepository(req.repo, hosts)
	explicit, explicitErr := settings.ParseRepository(a.options.repo, hosts)
	if selectedErr != nil || explicitErr != nil {
		return nil // Resolution reports the invalid one.
	}
	sameHost := selected.Host == "" || explicit.Host == "" || selected.Host == explicit.Host
	sameRepo := strings.EqualFold(selected.Name, explicit.Name) && (explicit.Owner == "" || strings.EqualFold(selected.Owner, explicit.Owner))
	if sameHost && sameRepo {
		return nil
	}
	return clierr.Wrap(clierr.Usage, fmt.Errorf("%s points to %s but --repo is %s", req.repoSource, selected.Slug(), a.options.repo))
}

// selectRepository parses raw into the target's repository and, for URLs and HOST/OWNER/REPO,
// its instance. With --host, URLs match only that instance.
func (a *application) selectRepository(ctx context.Context, t *target, s settings.Snapshot, raw string) error {
	configured := s.Hosts.Hosts
	if a.options.host != "" {
		explicit, err := settings.ResolveHost(a.options.host, configured)
		if err != nil {
			return clierr.Wrap(clierr.Usage, err)
		}
		if host, exists := configured[explicit]; exists {
			configured = map[string]settings.Host{explicit: host}
		}
	}
	ref, err := settings.ParseRepository(raw, configured)
	if err != nil {
		return clierr.Wrap(clierr.Usage, err)
	}
	if ref.Owner == "" && ref.Host == "" && a.isGitRemote(ctx, ref.Name) {
		return clierr.Wrap(clierr.Usage, fmt.Errorf("invalid repository %q: use OWNER/REPO, HOST/OWNER/REPO or a URL; did you mean --remote %s?", raw, ref.Name))
	}
	t.Repo = ref.Slug()
	if ref.Host != "" {
		t.Host, t.HostSource = ref.Host, t.RepoSource
	}
	return nil
}

// isGitRemote reports whether name is a remote of the working directory's Git checkout.
func (a *application) isGitRemote(ctx context.Context, name string) bool {
	remotes, err := a.gitProbe().Output(ctx, a.options.cwd, false, "remote")
	return err == nil && slices.Contains(strings.Fields(remotes), name)
}

// selectHost picks the instance: the repository's, --host, TEA_HOST or GITEA_INSTANCE_URL,
// default_host, or the only configured instance.
func (a *application) selectHost(t *target, s settings.Snapshot) error {
	if a.options.host != "" {
		explicit, err := settings.ResolveHost(a.options.host, s.Hosts.Hosts)
		if err != nil {
			return clierr.Wrap(clierr.Usage, err)
		}
		if t.Host != "" && t.Host != explicit {
			return clierr.Wrap(clierr.Usage, fmt.Errorf("--host %s conflicts with %s from %s", explicit, t.Host, t.HostSource))
		}
		t.Host, t.HostSource = explicit, "--host"
	}
	if t.Host == "" {
		for _, key := range []string{"TEA_HOST", "GITEA_INSTANCE_URL"} {
			if value := a.deps.Getenv(key); value != "" {
				host, err := settings.ResolveHost(value, s.Hosts.Hosts)
				if err != nil {
					return clierr.Wrap(clierr.Usage, fmt.Errorf("invalid %s: %w", key, err))
				}
				t.Host, t.HostSource = host, key
				break
			}
		}
	}
	if t.Host == "" && s.Preferences.DefaultHost != "" {
		t.Host, t.HostSource = s.Preferences.DefaultHost, "config.yml default_host"
	}
	if t.Host == "" && len(s.Hosts.Hosts) == 1 {
		for host := range s.Hosts.Hosts {
			t.Host, t.HostSource = host, "sole configured instance"
		}
	}
	if t.Host == "" {
		if len(s.Hosts.Hosts) == 0 {
			return clierr.Wrap(clierr.Usage, errors.New("no instance selected: log in with tea auth login, or pass --host"))
		}
		return clierr.Wrap(clierr.Usage, fmt.Errorf("instance required: select --host or set default_host (instances: %s)", strings.Join(slices.Sorted(maps.Keys(s.Hosts.Hosts)), ", ")))
	}
	return nil
}

// selectAccount picks the account: --user or TEA_USER, the instance's active account, its only
// account, or an interactive choice.
func (a *application) selectAccount(ctx context.Context, t *target, s settings.Snapshot, authenticate bool) error {
	users := t.host.Users
	t.User, t.UserSource = a.selectedUser()
	if matched, ok := matchAccount(users, t.User); ok {
		t.User = matched
	}
	if t.User == "" {
		t.User, t.UserSource = t.host.User, "active instance account"
	}
	if t.User != "" || len(users) == 0 {
		return nil
	}
	if len(users) == 1 {
		for user := range users {
			t.User, t.UserSource = user, "sole configured account"
		}
		return nil
	}
	if !authenticate || a.deps.Getenv("GITEA_TOKEN") != "" || !a.policy(s).CanPrompt(a.deps.Streams) || a.deps.Prompter == nil {
		return nil
	}
	selected, err := a.deps.Prompter.Input(ctx, "account ("+accountNames(users)+")")
	if err != nil {
		return err
	}
	matched, ok := matchAccount(users, strings.TrimSpace(selected))
	if !ok {
		return clierr.Wrap(clierr.Usage, t.accountError(strings.TrimSpace(selected)))
	}
	t.User, t.UserSource = matched, "interactive account selection"
	return nil
}

// accountError explains why user has no stored credential on the target's instance.
func (t target) accountError(user string) error {
	users := t.host.Users
	switch {
	case user != "" && len(users) > 0:
		return fmt.Errorf("account %q is not logged in on %s (accounts: %s)", user, t.Host, accountNames(users))
	case user != "":
		return fmt.Errorf("account %q is not logged in on %s; run tea auth login --host %s", user, t.Host, t.Host)
	case len(users) > 0:
		return fmt.Errorf("no active account on %s (accounts: %s); pass --user or run tea auth switch", t.Host, accountNames(users))
	}
	text := "no account for " + t.Host
	if t.HostSource != "--host" {
		text += " (instance from " + describeSource(t.HostSource) + ")"
	}
	return errors.New(text + "; run tea auth login --host " + t.Host + ", or use -R or --host to target another instance")
}

// describeSource words a target source for messages, such as git remote "origin".
func describeSource(source string) string {
	if remote, ok := strings.CutPrefix(source, "remote "); ok {
		return "git remote " + strconv.Quote(remote)
	}
	return source
}

func accountNames(users map[string]settings.Account) string {
	return strings.Join(slices.Sorted(maps.Keys(users)), ", ")
}

// selectedUser returns the account named by --user or TEA_USER, and which one named it.
func (a *application) selectedUser() (string, string) {
	if a.options.user != "" {
		return a.options.user, "--user"
	}
	return a.deps.Getenv("TEA_USER"), "TEA_USER"
}

func matchAccount(users map[string]settings.Account, selected string) (string, bool) {
	if selected == "" {
		return "", false
	}
	if _, ok := users[selected]; ok {
		return selected, true
	}
	for name := range users {
		if strings.EqualFold(name, selected) {
			return name, true
		}
	}
	return "", false
}