// internal/brain/client.go
// Package brain provides a lightweight client for querying the ingestion server.
// Skill handlers call Query before spawning workers to inject relevant knowledge
// from the brain into the task prompt. Errors are suppressed — the brain is
// optional context; its absence must never block a skill invocation.
package brain

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

type queryResult struct {
	Path    string `json:"path"`
	Title   string `json:"title"`
	Excerpt string `json:"excerpt"`
	Score   int    `json:"score"`
}

// Query calls the ingestion server and returns relevant knowledge as a
// formatted string ready to prepend to a worker task prompt.
// Returns empty string (no error) when baseURL or query is empty,
// when the brain is unreachable, or when no results are found.
func Query(ctx context.Context, baseURL, query string, limit int) (string, error) {
	if baseURL == "" || strings.TrimSpace(query) == "" {
		return "", nil
	}
	if limit <= 0 {
		limit = 3
	}

	body, _ := json.Marshal(map[string]any{"query": query, "limit": limit})
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, baseURL+"/query", bytes.NewReader(body))
	if err != nil {
		slog.Warn("brain: build request failed", "err", err)
		return "", nil
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		slog.Warn("brain: ingestion server unreachable", "err", err)
		return "", nil
	}
	defer func() { _ = resp.Body.Close() }()

	if resp.StatusCode != http.StatusOK {
		slog.Warn("brain: ingestion server returned non-OK", "status", resp.StatusCode)
		return "", nil
	}

	out, _ := io.ReadAll(resp.Body)
	var result struct {
		Results []queryResult `json:"results"`
	}
	if err := json.Unmarshal(out, &result); err != nil || len(result.Results) == 0 {
		return "", nil
	}

	var b strings.Builder
	b.WriteString("## Relevant knowledge\n\n")
	for _, r := range result.Results {
		title := r.Title
		if title == "" {
			title = r.Path
		}
		fmt.Fprintf(&b, "### %s\n%s\n\n", title, r.Excerpt)
	}
	return b.String(), nil
}