package db

import (
	"fmt"
	"strings"
)

// FailureAtlasEntry is one tier's aggregated failure rate for a fingerprint bucket.
type FailureAtlasEntry struct {
	Tier     string
	Total    int
	Failures int
	FailPct  float64
}

// FailureAtlasSummary returns a compact prosecutor-ready summary from tier_outcomes.
func (d *Database) FailureAtlasSummary(fingerprintKey, goos string) (string, error) {
	entries, err := d.failureAtlasEntries(fingerprintKey)
	if err != nil {
		return "", err
	}
	if len(entries) == 0 && goos != "" {
		entries, err = d.failureAtlasEntriesLike(goos + "|%")
		if err != nil {
			return "", err
		}
	}
	if len(entries) == 0 {
		return "no fleet failure atlas samples for this fingerprint", nil
	}
	parts := make([]string, 0, len(entries))
	for _, e := range entries {
		if e.Failures == 0 {
			continue
		}
		parts = append(parts, fmt.Sprintf("%s %d/%d failed (%.0f%%)", e.Tier, e.Failures, e.Total, e.FailPct))
	}
	if len(parts) == 0 {
		return "fleet atlas shows no tier failures for this fingerprint", nil
	}
	return strings.Join(parts, "; "), nil
}

func (d *Database) failureAtlasEntries(fingerprintKey string) ([]FailureAtlasEntry, error) {
	return d.queryFailureAtlas(`fingerprint_key = ?`, fingerprintKey)
}

func (d *Database) failureAtlasEntriesLike(pattern string) ([]FailureAtlasEntry, error) {
	return d.queryFailureAtlas(`fingerprint_key LIKE ?`, pattern)
}

func (d *Database) queryFailureAtlas(whereClause string, arg interface{}) ([]FailureAtlasEntry, error) {
	if d == nil {
		return nil, nil
	}
	query := fmt.Sprintf(`
		SELECT tier,
		       COUNT(*) AS total,
		       SUM(CASE WHEN ok = 0 THEN 1 ELSE 0 END) AS failures
		FROM tier_outcomes WHERE %s
		GROUP BY tier
		HAVING failures > 0
		ORDER BY failures DESC, total DESC
		LIMIT 12`, whereClause)
	rows, err := d.Query(query, arg)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []FailureAtlasEntry
	for rows.Next() {
		var e FailureAtlasEntry
		if err := rows.Scan(&e.Tier, &e.Total, &e.Failures); err != nil {
			return nil, err
		}
		if e.Total > 0 {
			e.FailPct = 100 * float64(e.Failures) / float64(e.Total)
		}
		out = append(out, e)
	}
	return out, rows.Err()
}