// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Test helpers for internal and external usage.

#![allow(missing_docs)]

use codec::{Decode, Encode};
use frame_support::{
	migrations::*,
	weights::{Weight, WeightMeter},
};
use sp_core::ConstU32;
use sp_runtime::BoundedVec;
use sp_std::{vec, vec::Vec};

/// Opaque identifier of a migration.
pub type MockedIdentifier = BoundedVec<u8, ConstU32<256>>;

/// How a mocked migration should behave.
#[derive(Debug, Clone, Copy, Encode, Decode)]
pub enum MockedMigrationKind {
	/// Succeed after its number of steps elapsed.
	SucceedAfter,
	/// Fail after its number of steps elapsed.
	FailAfter,
	/// Never terminate.
	TimeoutAfter,
	/// Cause an [`SteppedMigrationError::InsufficientWeight`] error after its number of steps
	/// elapsed.
	HighWeightAfter(Weight),
}
use MockedMigrationKind::*; // C style

/// Creates a migration identifier with a specific `kind` and `steps`.
pub fn mocked_id(kind: MockedMigrationKind, steps: u32) -> MockedIdentifier {
	(b"MockedMigration", kind, steps).encode().try_into().unwrap()
}

frame_support::parameter_types! {
	/// The configs for the migrations to run.
	storage MIGRATIONS: Vec<(MockedMigrationKind, u32)> = vec![];
}

/// Allows to set the migrations to run at runtime instead of compile-time.
///
/// It achieves this by using the storage to store the migrations to run.
pub struct MockedMigrations;
impl SteppedMigrations for MockedMigrations {
	fn len() -> u32 {
		MIGRATIONS::get().len() as u32
	}

	fn nth_id(n: u32) -> Option<Vec<u8>> {
		let k = MIGRATIONS::get().get(n as usize).copied();
		k.map(|(kind, steps)| mocked_id(kind, steps).into_inner())
	}

	fn nth_step(
		n: u32,
		cursor: Option<Vec<u8>>,
		_meter: &mut WeightMeter,
	) -> Option<Result<Option<Vec<u8>>, SteppedMigrationError>> {
		let (kind, steps) = MIGRATIONS::get()[n as usize];

		let mut count: u32 =
			cursor.as_ref().and_then(|c| Decode::decode(&mut &c[..]).ok()).unwrap_or(0);
		log::debug!("MockedMigration: Step {count} vs max {steps}");
		if count != steps || matches!(kind, TimeoutAfter) {
			count += 1;
			return Some(Ok(Some(count.encode())))
		}

		Some(match kind {
			SucceedAfter => {
				log::debug!("MockedMigration: Succeeded after {} steps", count);
				Ok(None)
			},
			HighWeightAfter(required) => {
				log::debug!("MockedMigration: Not enough weight after {} steps", count);
				Err(SteppedMigrationError::InsufficientWeight { required })
			},
			FailAfter => {
				log::debug!("MockedMigration: Failed after {} steps", count);
				Err(SteppedMigrationError::Failed)
			},
			TimeoutAfter => unreachable!(),
		})
	}

	fn nth_transactional_step(
		n: u32,
		cursor: Option<Vec<u8>>,
		meter: &mut WeightMeter,
	) -> Option<Result<Option<Vec<u8>>, SteppedMigrationError>> {
		// This is a hack but should be fine. We don't need it in testing.
		Self::nth_step(n, cursor, meter)
	}

	fn nth_max_steps(n: u32) -> Option<Option<u32>> {
		MIGRATIONS::get().get(n as usize).map(|(_, s)| Some(*s))
	}

	fn cursor_max_encoded_len() -> usize {
		65_536
	}

	fn identifier_max_encoded_len() -> usize {
		256
	}
}

impl MockedMigrations {
	/// Set the migrations to run.
	pub fn set(migrations: Vec<(MockedMigrationKind, u32)>) {
		MIGRATIONS::set(&migrations);
	}
}

impl crate::MockedMigrations for MockedMigrations {
	fn set_fail_after(steps: u32) {
		MIGRATIONS::set(&vec![(FailAfter, steps)]);
	}

	fn set_success_after(steps: u32) {
		MIGRATIONS::set(&vec![(SucceedAfter, steps)]);
	}
}