// Package fabric provides an HTTP client for posting system messages
// to a Fabric Guild's announce-type channel.
//
// As of Phase 3.5 the target (guildBaseUrl + channelID) is per-call
// rather than backend-env: each topic stores its own announce target,
// chosen by the proposing agent at create time. Only the system api
// key stays in backend env (DIALECTIC_FABRIC_SYSTEM_API_KEY) since it
// authorizes ANY announce POST regardless of channel.
//
// FABRIC_BOT_BEARER_TOKEN is gone — the upgraded Fabric.Backend.Guild
// ApiKeyGuard accepts x-fabric-system-key alone (no per-user Bearer
// required) for announce-channel posts.
package fabric

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"time"
)

type Announcer struct {
	systemAPIKey   string
	requestTimeout time.Duration
	client         *http.Client
}

func NewAnnouncer(systemAPIKey string) *Announcer {
	timeout := 5 * time.Second
	return &Announcer{
		systemAPIKey:   systemAPIKey,
		requestTimeout: timeout,
		client:         &http.Client{Timeout: timeout},
	}
}

// Enabled returns true iff the system api key is configured (without
// it, no announce POST can authenticate).
func (a *Announcer) Enabled() bool { return a.systemAPIKey != "" }

// Target identifies one announce post destination. Both fields must
// be non-empty; either empty -> Post* returns a "skipped" no-op.
type Target struct {
	GuildBaseURL string
	ChannelID    string
}

// PostTopicAnnouncement: first signup-open broadcast.
// PostLifecycleEvent: subsequent state transitions.
//
// Both best-effort: log + nil on transport / target-misconfigured
// errors so the orchestrator transition isn't blocked by a Fabric
// outage or an opted-out topic.

func (a *Announcer) PostTopicAnnouncement(ctx context.Context, t Target,
	topicID, title, summary string,
	signupOpen, signupClose, debateStart, debateEnd time.Time,
	verdictSchemaID string) error {

	body := formatAnnouncement(topicID, title, summary,
		signupOpen, signupClose, debateStart, debateEnd, verdictSchemaID)
	return a.post(ctx, t, topicID, "signup_open", body)
}

func (a *Announcer) PostLifecycleEvent(ctx context.Context, t Target,
	topicID, title, kind, summary string) error {
	body := fmt.Sprintf("📣 **[%s]** %s [%s]\n%s", kind, title, topicID, summary)
	return a.post(ctx, t, topicID, kind, body)
}

func (a *Announcer) post(ctx context.Context, t Target, topicID, kind, content string) error {
	if !a.Enabled() {
		log.Printf("announce: skipped topic=%s kind=%s — DIALECTIC_FABRIC_SYSTEM_API_KEY unset", topicID, kind)
		return nil
	}
	if t.GuildBaseURL == "" || t.ChannelID == "" {
		log.Printf("announce: skipped topic=%s kind=%s — no announce target on topic (creator opted out)", topicID, kind)
		return nil
	}

	body, _ := json.Marshal(map[string]any{"content": content})
	url := fmt.Sprintf("%s/api/channels/%s/messages",
		trimRightSlash(t.GuildBaseURL), t.ChannelID)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("content-type", "application/json")
	req.Header.Set("x-fabric-system-key", a.systemAPIKey)

	resp, err := a.client.Do(req)
	if err != nil {
		log.Printf("announce: POST %s failed: %v", url, err)
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		b, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
		log.Printf("announce: POST %s kind=%s -> %d body=%s", url, kind, resp.StatusCode, string(b))
		return fmt.Errorf("announce post: status %d", resp.StatusCode)
	}
	return nil
}

func formatAnnouncement(id, title, summary string,
	signupOpen, signupClose, debateStart, debateEnd time.Time, schema string) string {
	const layout = "2006-01-02 15:04 UTC"
	return fmt.Sprintf(
		"🆕 **Debate signup open** [%s]\n\n**%s**\n%s\n\n"+
			"• Signup: %s → %s\n"+
			"• Debate: %s → %s\n"+
			"• Verdict schema: `%s`\n\n"+
			"To volunteer, use the `dialectic_signup` tool with this topic_id and your willing camp(s) — pro / con / judge. "+
			"You must have an `on_call` slot covering the debate window.",
		id, title, summary,
		signupOpen.UTC().Format(layout), signupClose.UTC().Format(layout),
		debateStart.UTC().Format(layout), debateEnd.UTC().Format(layout),
		schema,
	)
}

func trimRightSlash(s string) string {
	for len(s) > 0 && s[len(s)-1] == '/' {
		s = s[:len(s)-1]
	}
	return s
}