import _ from "lodash";
import { AppData } from "../../data/app-data";
import type {
    BUN_MARIADB_INFORMATION_SCHEMA_TABLES,
    CreateDBSchemaParams,
} from "../../types";
import handleDBSchemaTable from "./handle-db-schema-table";
import getExistingTablesFromTablesManagerTable from "./get-existing-tables-from-tables-manager-table";
import MariaDBQuoteGen from "./mariadb-quote-gen";
import resolveTable from "./resolve-table";
import { ensureForeignKeys } from "./sync-foreign-keys";
import runSchemaQuery, { querySchemaRows } from "./run-schema-query";
import schemaCondition from "./schema-condition";
import { removeDbManagerTable } from "./upsert-db-manager-table";

export default async function handleDBSchemaTables(
    params: CreateDBSchemaParams,
) {
    const { db_schema, config } = params;

    /**
     * Grab Tables that have been recorded in the Schema
     * Manager Table
     */
    const existing_schema_tables =
        await getExistingTablesFromTablesManagerTable(params);

    const schemaCond = schemaCondition(config);
    const existing_live_tables =
        await querySchemaRows<BUN_MARIADB_INFORMATION_SCHEMA_TABLES>({
            query: `SELECT TABLE_NAME FROM information_schema.TABLES WHERE ${schemaCond.where} AND TABLE_TYPE = 'BASE TABLE' AND TABLE_NAME != ?`,
            values: [...schemaCond.values, AppData["DbSchemaManagerTableName"]],
            config,
        });

    for (let i = 0; i < db_schema.tables.length; i++) {
        const table = db_schema.tables[i];
        if (!table) continue;

        const existing_table = existing_schema_tables.find(
            (t) => t == table.tableName,
        );

        const existing_live_table = existing_live_tables.find(
            (t) => t.TABLE_NAME == table.tableName,
        );

        await handleDBSchemaTable({
            ...params,
            table,
            db_manager_table_name: existing_table,
            existing_live_table,
        });
    }

    /**
     * Foreign keys last: every referenced table now exists, so forward
     * references, self references and cycles between tables all resolve.
     */
    for (const table of db_schema.tables) {
        if (!table) continue;

        await ensureForeignKeys({
            table: resolveTable(table, db_schema),
            config,
        });
    }

    /**
     * Drop tables tracked by the manager but no longer in the schema.
     * Skip drops when remaining schema tables still reference the table via FK
     * (e.g. external tables like `users` that are referenced but not managed).
     */
    const schemaTableNames = db_schema.tables.map((t) => t.tableName);
    const tablesToDrop = _.uniq(
        existing_schema_tables.filter(
            (tableName): tableName is string =>
                Boolean(tableName) && !schemaTableNames.includes(tableName!),
        ),
    );

    if (tablesToDrop.length === 0) {
        return;
    }

    const fkRows = await querySchemaRows<{
        TABLE_NAME: string;
        REFERENCED_TABLE_NAME: string;
    }>({
        query: `SELECT TABLE_NAME, REFERENCED_TABLE_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE ${schemaCond.where} AND REFERENCED_TABLE_NAME IS NOT NULL`,
        values: schemaCond.values,
        config,
    });

    const referencedByRemaining = new Map<string, string[]>();
    for (const row of fkRows) {
        if (
            !row.REFERENCED_TABLE_NAME ||
            !tablesToDrop.includes(row.REFERENCED_TABLE_NAME)
        ) {
            continue;
        }

        // Referenced by a table we are keeping
        if (
            schemaTableNames.includes(row.TABLE_NAME) ||
            !tablesToDrop.includes(row.TABLE_NAME)
        ) {
            const list =
                referencedByRemaining.get(row.REFERENCED_TABLE_NAME) || [];
            if (!list.includes(row.TABLE_NAME)) {
                list.push(row.TABLE_NAME);
            }
            referencedByRemaining.set(row.REFERENCED_TABLE_NAME, list);
        }
    }

    const safeToDrop: string[] = [];

    for (const tableName of tablesToDrop) {
        const dependents = referencedByRemaining.get(tableName);
        if (dependents && dependents.length > 0) {
            console.warn(
                `Skipping drop of table \`${tableName}\`: still referenced by ${dependents.join(", ")}. Removing from schema manager tracking only.`,
            );
            await removeDbManagerTable({ tableName, config });
            continue;
        }
        safeToDrop.push(tableName);
    }

    if (safeToDrop.length === 0) {
        return;
    }

    await runSchemaQuery({ query: `SET FOREIGN_KEY_CHECKS = 0`, config });

    try {
        for (const tableName of safeToDrop) {
            console.log(`Dropping table: ${tableName}`);
            await runSchemaQuery({
                query: `DROP TABLE IF EXISTS ${MariaDBQuoteGen(tableName)}`,
                config,
            });
            await removeDbManagerTable({ tableName, config });
        }
    } finally {
        await runSchemaQuery({ query: `SET FOREIGN_KEY_CHECKS = 1`, config });
    }
}