package com.ankurm.expandcontract;

import com.ankurm.expandcontract.customer.Customer;
import com.ankurm.expandcontract.customer.CustomerService;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.io.TempDir;
import org.springframework.jdbc.core.simple.JdbcClient;

import java.nio.file.Path;

import static org.assertj.core.api.Assertions.assertThat;

/**
 * Deploy 4 (CONTRACT), in both directions. First the case that must work: once every
 * replica is confirmed on Stage 4 and the drop migration (V3) has run, Stage 4 code
 * keeps working exactly as before - it never referenced "email" to begin with. Second
 * the case that must fail loudly: a Stage 1, 2 or 3 instance that is somehow still
 * running against the post-drop schema (a rollback gone wrong, a forgotten canary)
 * gets a real SQL error the moment it tries to touch the column that no longer exists.
 * That failure is not a bug in this article's design - it is *why* Deploy 4 has to wait
 * for confirmation that the fleet is 100% on Stage 4 first. See
 * docs/09-the-contract-migration.md and docs/10-what-happens-if-you-drop-too-soon.md.
 */
class ContractSafetyTest {

    @Test
    void stage4KeepsWorkingAfterTheColumnIsDropped(@TempDir Path tmp) throws Exception {
        Path db = tmp.resolve("contract-ok");
        TestSupport.migrateTo(db, "2");
        JdbcClient jdbc = TestSupport.jdbcClient(db);
        Transcript t = Transcript.start("09-contract-safety",
                "Deploy 4 (CONTRACT): Stage 4 after the drop, and what breaks if you drop too soon");

        CustomerService stage4 = new CustomerService(jdbc, 4);
        long id = stage4.create("Annie Easley", "annie@example.test");

        // Deploy 4b: drop the old column, live, with Stage 4 already the only code running.
        TestSupport.migrateTo(db, "latest");

        Customer afterDrop = stage4.findById(id).orElseThrow();
        t.section("Stage 4 read, after V3 dropped the email column");
        t.line(afterDrop.toString());
        assertThat(afterDrop.email()).isEqualTo("annie@example.test");

        long postDropId = stage4.create("Mary Allen Wilkes", "mary@example.test");
        Customer postDrop = stage4.findById(postDropId).orElseThrow();
        t.section("Stage 4 create + read, entirely after the drop");
        t.line(postDrop.toString());
        assertThat(postDrop.email()).isEqualTo("mary@example.test");

        t.write();
    }

    @Test
    void stage1CodeFailsLoudlyIfItIsStillRunningAfterTheColumnIsDropped(@TempDir Path tmp) throws Exception {
        Path db = tmp.resolve("contract-too-soon");
        TestSupport.migrateTo(db, "latest");
        JdbcClient jdbc = TestSupport.jdbcClient(db);
        Transcript t = Transcript.start("10-drop-too-soon",
                "What a lingering Stage 1 instance sees if the drop runs before it is retired");

        CustomerService stage1 = new CustomerService(jdbc, 1);

        Throwable thrown = catchThrowable(() -> stage1.create("Too Late", "too.late@example.test"));
        Throwable root = thrown;
        while (root.getCause() != null) {
            root = root.getCause();
        }
        t.line("Stage 1 create() after V3 dropped \"email\": " + thrown.getClass().getName());
        t.line("message: " + thrown.getMessage());
        t.line("root cause: " + root.getClass().getName() + ": " + root.getMessage());
        assertThat(root.getMessage()).contains("EMAIL").containsIgnoringCase("not found");

        t.write();
    }

    private static Throwable catchThrowable(org.assertj.core.api.ThrowableAssert.ThrowingCallable callable) {
        try {
            callable.call();
            return new AssertionError("expected an exception but none was thrown");
        } catch (Throwable t) {
            return t;
        }
    }
}