Pete/internal/explainer/explainer.go

// Package explainer summarizes a posted story on demand: when a user reacts ❓
// on one of Pete's posts, Pete fetches the article body, asks Ollama for a
// 3-bullet TL;DR, and replies in a thread rooted at the original post.
package explainer

import (
	"fmt"
	"html"
	"log/slog"
	"strings"
	"sync"
	"time"

	"pete/internal/classifier"
	"pete/internal/ingestion"
	"pete/internal/matrix"
	"pete/internal/storage"

	"maunium.net/go/mautrix/id"
)

// QuestionEmoji is the reaction key that triggers a summary. Matrix delivers
// the reaction key verbatim — Element sends "❓" (U+2753).
const QuestionEmoji = "❓"

// cooldown for repeat-explain on the same story (per process).
const explainCooldown = 5 * time.Minute

// Explainer holds the dependencies needed to produce a story summary.
type Explainer struct {
	mx     *matrix.Client
	ollama *classifier.OllamaClient

	mu       sync.Mutex
	lastSeen map[string]time.Time // guid -> last explanation time
}

// New builds an Explainer wired to the Matrix client and Ollama backend.
func New(mx *matrix.Client, ollama *classifier.OllamaClient) *Explainer {
	return &Explainer{
		mx:       mx,
		ollama:   ollama,
		lastSeen: make(map[string]time.Time),
	}
}

// Handle is the entry point used as a callback from poster.HandleReaction.
// It runs synchronously — callers should invoke it in a goroutine.
func (e *Explainer) Handle(roomID id.RoomID, rootEventID id.EventID, guid, channel, emoji string) {
	if emoji != QuestionEmoji {
		return
	}
	if !e.acquire(guid) {
		slog.Debug("explain: skipping recent duplicate", "guid", guid)
		return
	}

	story, err := storage.GetStoryByGUID(guid)
	if err != nil || story == nil {
		slog.Warn("explain: story lookup failed", "guid", guid, "err", err)
		return
	}

	body := ingestion.FetchArticleBody(story.ArticleURL)
	if body == "" {
		// Couldn't get the body — fall back to lede so the user at least gets something.
		body = story.Lede
	}
	if body == "" {
		slog.Warn("explain: no body or lede available", "guid", guid, "url", story.ArticleURL)
		_ = e.mx.PostThreadedReply(channel, rootEventID,
			"Couldn't fetch the article body to summarize.",
			"<em>Couldn't fetch the article body to summarize.</em>")
		return
	}

	summary, err := e.summarize(story.Headline, body)
	if err != nil {
		slog.Error("explain: ollama failed", "guid", guid, "err", err)
		_ = e.mx.PostThreadedReply(channel, rootEventID,
			"Sorry, I couldn't generate a summary right now.",
			"<em>Sorry, I couldn't generate a summary right now.</em>")
		return
	}

	plain, htmlBody := formatSummary(summary)
	if err := e.mx.PostThreadedReply(channel, rootEventID, plain, htmlBody); err != nil {
		slog.Error("explain: send reply failed", "guid", guid, "err", err)
		return
	}
	slog.Info("explain: summary posted", "guid", guid, "channel", channel)
}

// acquire returns true if this guid hasn't been explained within the cooldown.
// Updates the timestamp on success.
func (e *Explainer) acquire(guid string) bool {
	e.mu.Lock()
	defer e.mu.Unlock()
	if t, ok := e.lastSeen[guid]; ok && time.Since(t) < explainCooldown {
		return false
	}
	e.lastSeen[guid] = time.Now()
	return true
}

const summarySystem = `You summarize news articles in exactly 3 short bullet points for a chat reader.
Rules:
- Output ONLY the 3 bullets, each on its own line, prefixed with "- ".
- No preamble, no headings, no closing remarks.
- Each bullet is one concise sentence (under 25 words).
- Stick strictly to facts in the article. Do not speculate.`

func (e *Explainer) summarize(headline, body string) (string, error) {
	prompt := fmt.Sprintf("Headline: %s\n\nArticle body:\n%s", headline, body)
	out, err := e.ollama.GenerateText(summarySystem, prompt)
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(out), nil
}

// formatSummary converts the LLM's "- bullet\n- bullet" output into a Matrix
// plain + HTML pair. Any stray prefixes ("Summary:", "•", "*") are normalized
// to "-" bullets.
func formatSummary(raw string) (plain, htmlBody string) {
	lines := strings.Split(raw, "\n")
	var bullets []string
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		// Normalize common bullet markers
		for _, prefix := range []string{"- ", "* ", "• ", "·"} {
			if strings.HasPrefix(line, prefix) {
				line = strings.TrimSpace(line[len(prefix):])
				break
			}
		}
		// Skip header-ish lines the model sometimes adds
		low := strings.ToLower(line)
		if strings.HasPrefix(low, "summary:") || strings.HasPrefix(low, "tl;dr") {
			continue
		}
		if line == "" {
			continue
		}
		bullets = append(bullets, line)
	}
	if len(bullets) == 0 {
		// Model produced something but we couldn't parse bullets — pass through.
		return raw, "<pre>" + html.EscapeString(raw) + "</pre>"
	}

	var pb, hb strings.Builder
	hb.WriteString("<ul>")
	for i, b := range bullets {
		if i > 0 {
			pb.WriteByte('\n')
		}
		pb.WriteString("• ")
		pb.WriteString(b)
		hb.WriteString("<li>")
		hb.WriteString(html.EscapeString(b))
		hb.WriteString("</li>")
	}
	hb.WriteString("</ul>")
	return pb.String(), hb.String()
}