// Schema Evolution Demo
// Demonstrates version tracking and automatic migrations

// ============================================================
// PART 1: Type-Declared Migrations
// ============================================================

// Define a versioned type with a migration from v1 to v2
type User @v2 {
    name: String,
    email: String,

    // Migration from v1: add default email
    from @v1 = { name: old.name, email: "unknown@example.com" }
}

// Create a v1 user
let v1_user = Schema.versioned("User", 1, { name: "Alice" })
let v1_version = Schema.getVersion(v1_user)  // 1

// Migrate to v2 - uses the declared migration automatically
let v2_user = Schema.migrate(v1_user, 2)
let v2_version = Schema.getVersion(v2_user)  // 2

// ============================================================
// PART 2: Runtime Schema Operations (separate type)
// ============================================================

// Create versioned values for a different type (no migration)
let config1 = Schema.versioned("Config", 1, "debug")
let config2 = Schema.versioned("Config", 2, "release")

// Check versions
let c1 = Schema.getVersion(config1)  // 1
let c2 = Schema.getVersion(config2)  // 2

// Migrate config (auto-migration since no explicit migration defined)
let upgradedConfig = Schema.migrate(config1, 2)
let upgradedConfigVersion = Schema.getVersion(upgradedConfig)  // 2

// ============================================================
// PART 2: Practical Example - API Versioning
// ============================================================

// Simulate different API response versions
fn createResponseV1(data: String): { version: Int, payload: String } =
    { version: 1, payload: data }

fn createResponseV2(data: String, timestamp: Int): { version: Int, payload: String, meta: { ts: Int } } =
    { version: 2, payload: data, meta: { ts: timestamp } }

// Version-aware processing
fn getPayload(response: { version: Int, payload: String }): String =
    response.payload

let resp1 = createResponseV1("Hello")
let resp2 = createResponseV2("World", 1234567890)

let payload1 = getPayload(resp1)
let payload2 = resp2.payload

// ============================================================
// RESULTS
// ============================================================

fn main(): Unit with {Console} = {
    Console.print("=== Schema Evolution Demo ===")
    Console.print("")
    Console.print("Part 1: Type-declared migrations")
    Console.print("  User before migration: v" + toString(v1_version))
    Console.print("  User after migration: v" + toString(v2_version))
    Console.print("")
    Console.print("Part 2: Runtime schema operations")
    Console.print("  Config v1 version: " + toString(c1))
    Console.print("  Config v2 version: " + toString(c2))
    Console.print("  After upgrade: " + toString(upgradedConfigVersion))
    Console.print("")
    Console.print("Part 3: API versioning")
    Console.print("  Response v1 payload: " + payload1)
    Console.print("  Response v2 payload: " + payload2)
}

let output = run main() with {}