'use strict';

var createDebug = require('debug');
var builder = require('./builder.js');
var diff = require('./diff.js');
var storage = require('./storage.js');
var schema = require('./schema.js');

const debug = createDebug('strapi::database');
const createSchemaProvider = (db)=>{
    const state = {};
    return {
        get schema () {
            if (!state.schema) {
                debug('Converting metadata to database schema');
                state.schema = schema.metadataToSchema(db.metadata);
            }
            return state.schema;
        },
        builder: builder(db),
        schemaDiff: diff(db),
        schemaStorage: storage(db),
        /**
     * Drops the database schema
     */ async drop () {
            debug('Dropping database schema');
            const DBSchema = await db.dialect.schemaInspector.getSchema();
            await this.builder.dropSchema(DBSchema);
        },
        /**
     * Creates the database schema
     */ async create () {
            debug('Created database schema');
            await this.builder.createSchema(this.schema);
        },
        /**
     * Resets the database schema
     */ async reset () {
            debug('Resetting database schema');
            await this.drop();
            await this.create();
        },
        async syncSchema () {
            debug('Synchronizing database schema');
            const databaseSchema = await db.dialect.schemaInspector.getSchema();
            const storedSchema = await this.schemaStorage.read();
            /*
        3way diff - DB schema / previous metadataSchema / new metadataSchema

        - When something doesn't exist in the previous metadataSchema -> It's not tracked by us and should be ignored
        - If no previous metadataSchema => use new metadataSchema so we start tracking them and ignore everything else
        - Apply this logic to Tables / Columns / Indexes / FKs ...
        - Handle errors (indexes or fks on incompatible stuff ...)

      */ const { status, diff } = await this.schemaDiff.diff({
                previousSchema: storedSchema?.schema,
                databaseSchema,
                userSchema: this.schema
            });
            if (status === 'CHANGED') {
                await this.builder.updateSchema(diff);
            }
            await this.schemaStorage.add(this.schema);
            return status;
        },
        // TODO: support options to migrate softly or forcefully
        // TODO: support option to disable auto migration & run a CLI command instead to avoid doing it at startup
        // TODO: Allow keeping extra indexes / extra tables / extra columns (globally or on a per table basis)
        async sync () {
            if (await db.migrations.shouldRun()) {
                debug('Found migrations to run');
                await db.migrations.up();
                return this.syncSchema();
            }
            const oldSchema = await this.schemaStorage.read();
            if (!oldSchema) {
                debug('Schema not persisted yet');
                return this.syncSchema();
            }
            const { hash: oldHash } = oldSchema;
            const hash = await this.schemaStorage.hashSchema(this.schema);
            if (oldHash !== hash) {
                debug('Schema changed');
                return this.syncSchema();
            }
            debug('Schema unchanged');
            return 'UNCHANGED';
        }
    };
};

exports.createSchemaProvider = createSchemaProvider;
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