better-auth/docs/lib/copy-schema/dialects/mssql.ts

import type {
	DBFieldAttribute,
	Resolver,
	ResolverHandlerContext,
} from "../types";
import {
	filterForeignKeys,
	filterNonUniqueIndexes,
	getIndexName,
	getTypeFactory,
} from "../utils";

type CustomResolverContext = ResolverHandlerContext & {
	getType: ReturnType<typeof getTypeFactory>;
};

const formatField = (field: DBFieldAttribute, ctx: CustomResolverContext) => {
	let out = `[${field.fieldName}] ${ctx.getType(field)}`;

	if (field.required !== false) {
		out += " NOT NULL";
	}

	if (field.fieldName === "id") {
		out += " PRIMARY KEY";
	}

	if (field.unique) {
		out += " UNIQUE";
	}

	out += ",";
	return out;
};

const formatForeignKey = (field: DBFieldAttribute) => {
	let newLine = `FOREIGN KEY ([${field.fieldName}]) REFERENCES [${field.references!.model}]([${field.references!.field}])`;

	if (field.references!.onDelete) {
		newLine += ` ON DELETE ${field.references!.onDelete.toUpperCase()}`;
	}

	newLine += ",";
	return newLine;
};

const escapeSqlString = (value: string) => value.replace(/'/g, "''");

const formatIndex = (field: DBFieldAttribute, tableName: string) => {
	const indexName = getIndexName(tableName, field);
	const tableObject = escapeSqlString(tableName);
	return [
		`IF OBJECT_ID(N'${tableObject}') IS NOT NULL`,
		"\tAND NOT EXISTS (",
		"\t\tSELECT 1",
		"\t\tFROM sys.indexes",
		`\t\tWHERE name = N'${escapeSqlString(indexName)}'`,
		`\t\t\tAND object_id = OBJECT_ID(N'${tableObject}')`,
		"\t)",
		"BEGIN",
		`\tCREATE INDEX [${indexName}] ON [${tableName}] ([${field.fieldName}]);`,
		"END;",
	].join("\n");
};

export const mssqlResolver = {
	handler: (ctx) => {
		const getType = getTypeFactory((field) => ({
			string:
				field.unique || field.sortable
					? "varchar(255)"
					: field.references
						? "varchar(36)"
						: field.index
							? "varchar(255)"
							: "varchar(8000)",
			boolean: "smallint",
			number: field.bigint ? "bigint" : "integer",
			date: "datetime2(3)",
			json: "varchar(8000)",
			id: ctx.useNumberId ? "integer" : "varchar(36)",
			foreignKeyId: ctx.useNumberId ? "integer" : "varchar(36)",
		}));
		const lines = [
			`IF OBJECT_ID('${ctx.schema.modelName}') IS ${ctx.mode === "create" ? "NULL" : "NOT NULL"}`,
			"BEGIN",
			ctx.mode === "create"
				? `\tCREATE TABLE [${ctx.schema.modelName}] (`
				: `\tALTER TABLE [${ctx.schema.modelName}]`,
		];
		const fields = [];
		for (const field of ctx.schema.fields) {
			fields.push(
				`\t\t${ctx.mode === "alter" ? "ADD " : ""}${formatField(field, {
					...ctx,
					getType,
				})}`,
			);
		}
		for (const field of filterForeignKeys(ctx.schema)) {
			fields.push(
				`\t\t${ctx.mode === "alter" ? "ADD " : ""}${formatForeignKey(field)}`,
			);
		}
		const lastLineIdx = fields.length - 1;
		if (fields[lastLineIdx].endsWith(",")) {
			const str = fields[lastLineIdx].slice(0, -1);
			fields[lastLineIdx] = ctx.mode === "create" ? str : `${str};`;
		}
		lines.push(...fields);
		if (ctx.mode === "create") {
			lines.push(`\t);`);
		}
		lines.push("END;");
		for (const field of filterNonUniqueIndexes(ctx.schema)) {
			lines.push(formatIndex(field, ctx.schema.modelName));
		}
		return lines.join("\n");
	},
} satisfies Resolver;