package db

import (
	"database/sql"
	_ "embed"
	"fmt"

	_ "modernc.org/sqlite"
)

//go:embed schema.sql
var schemaSQL string

func Open(path string) (*sql.DB, error) {
	dsn := fmt.Sprintf("file:%s?_pragma=journal_mode(WAL)&_pragma=foreign_keys(ON)&_pragma=busy_timeout(5000)", path)
	conn, err := sql.Open("sqlite", dsn)
	if err != nil {
		return nil, fmt.Errorf("open sqlite: %w", err)
	}
	if err := conn.Ping(); err != nil {
		conn.Close()
		return nil, fmt.Errorf("ping sqlite: %w", err)
	}
	if _, err := conn.Exec(schemaSQL); err != nil {
		conn.Close()
		return nil, fmt.Errorf("apply schema: %w", err)
	}
	if err := addColumnIfMissing(conn, "items", "min_price", "REAL"); err != nil {
		conn.Close()
		return nil, err
	}
	if err := addColumnIfMissing(conn, "items", "exclude_keywords", "TEXT"); err != nil {
		conn.Close()
		return nil, err
	}
	if err := addColumnIfMissing(conn, "results", "matched_query", "TEXT"); err != nil {
		conn.Close()
		return nil, err
	}
	if err := addColumnIfMissing(conn, "items", "condition", "TEXT"); err != nil {
		conn.Close()
		return nil, err
	}
	if err := addColumnIfMissing(conn, "items", "region", "TEXT"); err != nil {
		conn.Close()
		return nil, err
	}
	if err := addColumnIfMissing(conn, "items", "best_price_currency", "TEXT"); err != nil {
		conn.Close()
		return nil, err
	}
	if err := addColumnIfMissing(conn, "results", "ends_at", "DATETIME"); err != nil {
		conn.Close()
		return nil, err
	}
	// Per-user item ownership. On a migrated DB the column is added without a
	// REFERENCES clause (ALTER TABLE ADD COLUMN can't carry one cleanly), then
	// orphaned items are assigned to the first admin (or, failing that, the
	// first user) so the operator keeps their existing watchlist. Fresh DBs get
	// the FK from schema.sql and have no rows to backfill.
	if err := addColumnIfMissing(conn, "items", "user_id", "INTEGER"); err != nil {
		conn.Close()
		return nil, err
	}
	if _, err := conn.Exec(`
		UPDATE items SET user_id = (
			SELECT id FROM users
			ORDER BY (role = 'admin') DESC, id ASC
			LIMIT 1
		)
		WHERE user_id IS NULL AND EXISTS (SELECT 1 FROM users)
	`); err != nil {
		conn.Close()
		return nil, fmt.Errorf("backfill item ownership: %w", err)
	}
	if _, err := conn.Exec(`CREATE INDEX IF NOT EXISTS idx_items_user ON items(user_id)`); err != nil {
		conn.Close()
		return nil, fmt.Errorf("create items user index: %w", err)
	}
	// Multi-user / email columns (Authentik forward-auth + Resend mail).
	for _, c := range []struct{ col, typ string }{
		{"email", "TEXT"},
		{"auth_source", "TEXT NOT NULL DEFAULT 'local'"},
		{"email_deal_alerts", "INTEGER NOT NULL DEFAULT 0"},
		{"email_weekly_digest", "INTEGER NOT NULL DEFAULT 0"},
	} {
		if err := addColumnIfMissing(conn, "users", c.col, c.typ); err != nil {
			conn.Close()
			return nil, err
		}
	}
	// Email is the identity key for forward-auth (Authentik) and the Resend
	// destination. Partial unique index: many local users may have no email
	// (NULL/'') while any populated address stays unique. Created here, after
	// the email column exists, so it works on both fresh and migrated DBs.
	if _, err := conn.Exec(`CREATE UNIQUE INDEX IF NOT EXISTS idx_users_email
		ON users(email) WHERE email IS NOT NULL AND email != ''`); err != nil {
		conn.Close()
		return nil, fmt.Errorf("create users email index: %w", err)
	}
	return conn, nil
}

func addColumnIfMissing(conn *sql.DB, table, column, typ string) error {
	rows, err := conn.Query(fmt.Sprintf(`PRAGMA table_info(%s)`, table))
	if err != nil {
		return fmt.Errorf("inspect %s: %w", table, err)
	}
	defer rows.Close()
	for rows.Next() {
		var cid int
		var name, ctype string
		var notnull, pk int
		var dflt sql.NullString
		if err := rows.Scan(&cid, &name, &ctype, &notnull, &dflt, &pk); err != nil {
			return err
		}
		if name == column {
			return nil
		}
	}
	if _, err := conn.Exec(fmt.Sprintf(`ALTER TABLE %s ADD COLUMN %s %s`, table, column, typ)); err != nil {
		return fmt.Errorf("add column %s.%s: %w", table, column, err)
	}
	return nil
}