import { defineNuxtModule } from '@nuxt/kit'
import { Database } from "bun:sqlite";

interface Schema
{
    type: string;
    name: string;
    tbl_name: string;
    sql: string;
}
interface Structure
{
    cid: number;
    name: string;
    type: string;
    [key: string]: number | string | null;
}

export default defineNuxtModule({
  setup (options, nuxt) {
    nuxt.hook('build:done', () => {
        console.log("Building database");

        const template = new Database(nuxt.options.runtimeConfig.templateFile);
        const schema = template.query(`SELECT * FROM sqlite_schema WHERE type = 'table'`).all() as Schema[];
        const structure = template.query(`SELECT * FROM pragma_table_info(?1)`);

        const db = new Database(nuxt.options.runtimeConfig.dbFile);
        db.exec(`PRAGMA foreign_keys = OFF; PRAGMA defer_foreign_keys = OFF;`);
        const oldSchema = db.query(`SELECT * FROM sqlite_schema WHERE type = 'table'`).all() as Schema[];
        const oldStructure = db.query(`SELECT * FROM pragma_table_info(?1)`);

        (db.transaction((tables: Schema[], oldTables: Schema[]) => {
            for(const table of tables)
            {
                const oldIdx = oldTables.findIndex(e => e.name === table.name);

                if(table.name === 'sqlite_sequence')
                {
                    oldTables.splice(oldIdx, 1);
                    continue;
                }
                
                const columns = structure.all(table.name) as Structure[];
                const oldColumns = oldStructure.all(table.name) as Structure[];

                if(oldIdx !== -1)
                {
                    oldTables.splice(oldIdx, 1);

                    const filteredColumns = oldColumns.filter(e => columns.find(f => e.name === f.name)).map(e => `"${e.name}"`).join(', ')

                    db.exec(table.sql.replace(`CREATE TABLE "${table.name}"`, `CREATE TABLE "${table.name}_new"`));
                    db.exec(`INSERT INTO ${table.name}_new (${filteredColumns}) SELECT ${filteredColumns} FROM ${table.name}`);
                    db.exec(`DROP TABLE ${table.name}`);
                    db.exec(`ALTER TABLE ${table.name}_new RENAME TO ${table.name}`);
                }
                else
                {
                    db.exec(table.sql);
                }
            }
            for(const table of oldTables)
            {
                db.exec(`DROP TABLE ${table.name}`);
            }
        })).immediate(schema, oldSchema);

        db.exec(`PRAGMA foreign_keys = ON; PRAGMA foreign_keys = ON;`);

        db.close();
        template.close();
    });
  }
})