package masterdb

import (
	"database/sql"
	"fmt"
	"time"
)

// Placement records which node hosts which service.
type Placement struct {
	ServiceName string
	Node        string
	Tier        string
	DeployedAt  time.Time
}

// CreatePlacement inserts or replaces a placement record.
func CreatePlacement(db *sql.DB, serviceName, node, tier string) error {
	_, err := db.Exec(`
		INSERT INTO placements (service_name, node, tier, deployed_at)
		VALUES (?, ?, ?, datetime('now'))
		ON CONFLICT(service_name) DO UPDATE SET
			node = excluded.node,
			tier = excluded.tier,
			deployed_at = datetime('now')
	`, serviceName, node, tier)
	if err != nil {
		return fmt.Errorf("create placement %s: %w", serviceName, err)
	}
	return nil
}

// GetPlacement returns the placement for a service.
func GetPlacement(db *sql.DB, serviceName string) (*Placement, error) {
	var p Placement
	var deployedAt string
	err := db.QueryRow(`
		SELECT service_name, node, tier, deployed_at
		FROM placements WHERE service_name = ?
	`, serviceName).Scan(&p.ServiceName, &p.Node, &p.Tier, &deployedAt)
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("get placement %s: %w", serviceName, err)
	}
	p.DeployedAt, _ = time.Parse("2006-01-02 15:04:05", deployedAt)
	return &p, nil
}

// ListPlacements returns all placements.
func ListPlacements(db *sql.DB) ([]*Placement, error) {
	rows, err := db.Query(`SELECT service_name, node, tier, deployed_at FROM placements ORDER BY service_name`)
	if err != nil {
		return nil, fmt.Errorf("list placements: %w", err)
	}
	defer func() { _ = rows.Close() }()

	var placements []*Placement
	for rows.Next() {
		var p Placement
		var deployedAt string
		if err := rows.Scan(&p.ServiceName, &p.Node, &p.Tier, &deployedAt); err != nil {
			return nil, fmt.Errorf("scan placement: %w", err)
		}
		p.DeployedAt, _ = time.Parse("2006-01-02 15:04:05", deployedAt)
		placements = append(placements, &p)
	}
	return placements, rows.Err()
}

// DeletePlacement removes a placement record.
func DeletePlacement(db *sql.DB, serviceName string) error {
	_, err := db.Exec(`DELETE FROM placements WHERE service_name = ?`, serviceName)
	if err != nil {
		return fmt.Errorf("delete placement %s: %w", serviceName, err)
	}
	return nil
}

// CountPlacementsPerNode returns a map of node name → number of placed services.
func CountPlacementsPerNode(db *sql.DB) (map[string]int, error) {
	rows, err := db.Query(`SELECT node, COUNT(*) FROM placements GROUP BY node`)
	if err != nil {
		return nil, fmt.Errorf("count placements: %w", err)
	}
	defer func() { _ = rows.Close() }()

	counts := make(map[string]int)
	for rows.Next() {
		var node string
		var count int
		if err := rows.Scan(&node, &count); err != nil {
			return nil, fmt.Errorf("scan count: %w", err)
		}
		counts[node] = count
	}
	return counts, rows.Err()
}