// Package adaptercfg derives the adapter's configuration from the resolved
// presence and OpenBao.
//
// The adapter publishes. It holds a bot token with post_messages and a single
// chat id, and it has no MTProto session and no provisioning code path. That
// separation is the point of running two planes: a compromised adapter cannot
// create, rename, delete or re-permission anything.
package adaptercfg

import (
	"context"
	"fmt"
	"strings"

	"github.com/tegwick/fluid-telegram/internal/secrets"
	"github.com/tegwick/fluid-telegram/internal/spec"
	"github.com/tegwick/fluid-telegram/internal/state"
)

// Config is what one adapter instance needs to publish to one channel.
type Config struct {
	Campaign string
	Channel  string
	ChatID   int64
	TokenRef string
}

// FromResolved maps the committed state onto one adapter instance. It never
// reads a secret: the token stays in OpenBao, and TokenRef is where to ask.
func FromResolved(rs *state.Resolved, channel, tokenRef string) (Config, error) {
	if rs == nil || rs.Bot.ID == 0 {
		return Config{}, fmt.Errorf("presence is not provisioned; run `provision apply` first")
	}
	switch channel {
	case spec.Test, spec.Live:
	case "":
		return Config{}, fmt.Errorf("--channel is required (%q or %q)", spec.Test, spec.Live)
	default:
		return Config{}, fmt.Errorf("channel %q is not %q or %q", channel, spec.Test, spec.Live)
	}
	ch, ok := rs.Channels[channel]
	if !ok {
		if channel == spec.Live && !rs.TestChannelVerified(spec.Test) {
			return Config{}, fmt.Errorf("the public channel is not provisioned yet; " +
				"it is held until the test channel has a checked rendering")
		}
		return Config{}, fmt.Errorf("channel %q is not in the resolved state", channel)
	}
	if ch.ChatID == 0 {
		return Config{}, fmt.Errorf("channel %q has no chat id in the resolved state", channel)
	}
	return Config{
		Campaign: rs.Campaign,
		Channel:  channel,
		ChatID:   BotAPIChatID(ch.ChatID),
		TokenRef: tokenRef,
	}, nil
}

// BotAPIChatID converts a channel id as the provisioner records it (the
// MTProto channel id, positive) into the form the Bot API addresses it by
// (-100 followed by the id). An id that is already negative is in Bot API
// form and is returned unchanged.
func BotAPIChatID(id int64) int64 {
	if id > 0 {
		return -1000000000000 - id
	}
	return id
}

// EnvFile is the non-secret configuration an adapter process is started with.
// The token is named, not emitted: the runtime injects it from OpenBao.
func (c Config) EnvFile() string {
	var b strings.Builder
	fmt.Fprintf(&b, "# adapter configuration for %s / %s\n", c.Campaign, c.Channel)
	fmt.Fprintf(&b, "# derived from presence/resolved/%s.yaml; no secrets in this file\n", c.Campaign)
	fmt.Fprintf(&b, "TELEGRAM_CHANNEL_ID=%d\n", c.ChatID)
	fmt.Fprintf(&b, "TELEGRAM_BOT_TOKEN_REF=%s\n", c.TokenRef)
	return b.String()
}

// LoadToken reads the bot token and nothing else. The operator session is a
// full-account credential; the adapter must never request it.
func LoadToken(ctx context.Context, store *secrets.Store) (string, error) {
	fields, found, err := store.Get(ctx, secrets.KeyBotToken)
	if err != nil {
		return "", err
	}
	if !found {
		return "", fmt.Errorf("no bot token at %s; run `provision apply`", store.Ref(secrets.KeyBotToken))
	}
	token := fields["token"]
	if token == "" {
		return "", fmt.Errorf("bot token at %s is empty", store.Ref(secrets.KeyBotToken))
	}
	return token, nil
}