import type {
    BUN_SQLITE_TableSchemaType,
    CreateDBSchemaParams,
} from "../../types";
import { sqlQuoteIdent as q } from "../../utils/sql-safe";
import checkIfTableExists from "./check-if-table-exists";
import createTable from "./create-table";
import getTableColumns from "./get-table-columns";
import resolveTable from "./resolve-table";

type Params = CreateDBSchemaParams & {
    table: BUN_SQLITE_TableSchemaType;
};

/**
 * # Update an existing table
 * @description SQLite has limited ALTER TABLE support, so the table is
 * rebuilt: create a temp table with the new schema, copy the data over,
 * drop the old table and rename the temp table.
 */
export default function updateTable(params: Params) {
    const { db, db_schema, table } = params;

    console.log(`Updating table: ${table.tableName}`);

    if (table.isVector) {
        recreateVectorTable(params);
        return;
    }

    const tempTableName = `${table.tableName}_temp_${Date.now()}`;

    // Columns are matched by name only: SQLite converts values to the new
    // column affinity on copy, so a type change keeps the data instead of
    // silently dropping the column.
    const existingColumns = getTableColumns({ db, table_name: table.tableName });
    const columnsToKeep = resolveTable({ table, db_schema })
        .fields.filter(
            (f) =>
                f.fieldName &&
                existingColumns.find((c) => c.name == f.fieldName),
        )
        .map((f) => f.fieldName as string);

    // Create temp table with new schema
    createTable({ ...params, table: { ...table, tableName: tempTableName } });

    // Copy data if there are common columns
    if (columnsToKeep.length > 0) {
        const columnList = columnsToKeep.map(q).join(", ");
        db.run(
            `INSERT INTO ${q(tempTableName)} (${columnList}) SELECT ${columnList} FROM ${q(table.tableName)}`,
        );
    }

    db.run(`DROP TABLE ${q(table.tableName)}`);
    db.run(`ALTER TABLE ${q(tempTableName)} RENAME TO ${q(table.tableName)}`);
}

/**
 * Vector tables are only rebuilt when `recreate_vector_table` is set.
 */
function recreateVectorTable(params: Params) {
    const { db, table, recreate_vector_table } = params;

    if (!recreate_vector_table) {
        return;
    }

    let existingRows: { [k: string]: any }[] = [];

    if (checkIfTableExists({ db, table_name: table.tableName })) {
        existingRows = db
            .query(`SELECT * FROM ${q(table.tableName)}`)
            .all() as { [k: string]: any }[];

        db.run(`DROP TABLE ${q(table.tableName)}`);
    }

    createTable(params);

    for (const row of existingRows) {
        const columns = Object.keys(row);
        const placeholders = columns.map(() => "?").join(", ");

        db.run(
            `INSERT INTO ${q(table.tableName)} (${columns.map(q).join(", ")}) VALUES (${placeholders})`,
            Object.values(row),
        );
    }
}