// Package databasePlatform
// Path: /internal/platform/database
// File: schema.go
//
// Purpose
//   Bootstrap and verify the initial application schema for MySQL using
//   embedded SQL. Applies the full schema only when the target database
//   is detected as "empty" via a probe query.
//
// Responsibilities (as implemented here)
//   1) Detect whether the schema has been initialized by probing the users table.
//   2) If empty, apply the embedded initial schema inside a single transaction.
//   3) Use helper ExecScript to execute multi-statement SQL safely.
//   4) Fail fast with contextual errors on probe/apply failures.
//
// Idempotency strategy
//   - Uses migrationSQL.ProbeUsersTable to query a known table and count rows.
//   - If count > 0, assumes schema exists and exits without applying SQL.
//   - This makes startup safe to repeat across restarts.
//
// Design notes
//   - InitialSchema is embedded (no external SQL files at runtime).
//   - Application is all-or-nothing via a single transaction.
//   - Console prints currently provide debug visibility during boot.
//   - Probe focuses on the "users" table as the presence indicator.
//
// TODOs (observations from current implementation)
//   - Replace debug prints with structured logging (levelled).
//   - Consider probing for table existence rather than row count to avoid
//     the edge case where users table exists but has zero rows.
//   - Introduce a schema version table for forward migrations.
//   - Expand error context to include which statement failed in ExecScript.
//
// Change log
//   [2025-10-29] Documentation aligned with embedded migrations and probe logic.

package databasePlatform

import (
	"database/sql"
	"fmt"

	databaseHelpers "synlotto-website/internal/helpers/database"
	migrationSQL "synlotto-website/internal/storage/migrations"
)

// EnsureInitialSchema ensures the database contains the baseline schema.
// If the probe indicates an existing install, the function is a no-op.
func EnsureInitialSchema(db *sql.DB) error {
	fmt.Println("✅ EnsureInitialSchema called") // temp debug

	// Probe: if users table exists & has rows, treat schema as present.
	var cnt int
	if err := db.QueryRow(migrationSQL.ProbeUsersTable).Scan(&cnt); err != nil {
		return fmt.Errorf("probe users table failed: %w", err)
	}
	fmt.Printf("👀 Probe users count = %d\n", cnt) // temp debug
	if cnt > 0 {
		return nil
	}

	// Sanity: visibility for embedded SQL payload size.
	fmt.Printf("📦 Initial SQL bytes: %d\n", len(migrationSQL.InitialSchema)) // temp debug

	// Apply full schema atomically.
	tx, err := db.Begin()
	if err != nil {
		return err
	}
	if err := databaseHelpers.ExecScript(tx, migrationSQL.InitialSchema); err != nil {
		_ = tx.Rollback()
		return fmt.Errorf("apply schema: %w", err)
	}
	return tx.Commit()
}