# Owner(s): ["oncall: distributed"]

import sys

import torch
from torch.distributed.checkpoint.planner import LoadItemType, WriteItemType

from torch.distributed._shard.sharded_tensor import (
    Shard,
    ShardMetadata,
    ShardedTensor,
    ShardedTensorMetadata,
)
from torch.distributed._shard.sharded_tensor.metadata import TensorProperties

from torch.testing._internal.common_utils import (
    TestCase,
    TEST_WITH_DEV_DBG_ASAN,
    run_tests,
)
from torch.distributed.checkpoint.metadata import BytesStorageMetadata, MetadataIndex, TensorStorageMetadata
from torch.testing._internal.distributed.distributed_utils import (
    with_fake_comms,
    with_dist
)

from torch.distributed.checkpoint.default_planner import (
    create_default_global_save_plan,
    create_default_local_save_plan,
    create_default_local_load_plan,
    _create_default_local_metadata
)

if TEST_WITH_DEV_DBG_ASAN:
    print(
        "Skip dev-asan as torch + multiprocessing spawn have known issues",
        file=sys.stderr,
    )
    sys.exit(0)

def create_sharded_tensor(rank, world_size, shards_per_rank, shard_size=8):
    shards_metadata = []
    local_shards = []
    for idx in range(0, world_size * shards_per_rank):
        shard_rank = idx // shards_per_rank
        shard_md = ShardMetadata(shard_offsets=[idx * shard_size], shard_sizes=[shard_size], placement=f"rank:{shard_rank}/cpu")
        shards_metadata.append(shard_md)
        if shard_rank == rank:
            shard = Shard.from_tensor_and_offsets(
                torch.rand(*shard_md.shard_sizes),
                shard_offsets=shard_md.shard_offsets,
                rank=rank
            )
            local_shards.append(shard)

    sharded_tensor_md = ShardedTensorMetadata(
        shards_metadata=shards_metadata,
        size=torch.Size([shard_size * len(shards_metadata)]),
        tensor_properties=TensorProperties.create_from_tensor(torch.zeros(1))
    )

    return ShardedTensor._init_from_local_shards_and_global_metadata(
        local_shards=local_shards,
        sharded_tensor_metadata=sharded_tensor_md
    )


class TestSavePlan(TestCase):
    @with_fake_comms(rank=1, world_size=4)
    def test_local_plan(self):
        tensor = torch.rand(10)
        val = [1, 2, 3]
        st = create_sharded_tensor(rank=1, world_size=4, shards_per_rank=1)
        state_dict = {
            "tensor": tensor,
            "value": val,
            "st": st
        }
        plan = create_default_local_save_plan(state_dict, False)
        self.assertEqual(1, len(plan.items))
        wi = plan.items[0]
        self.assertEqual(wi.index, MetadataIndex("st", [8]))
        self.assertEqual(wi.type, WriteItemType.SHARD)
        self.assertEqual(wi.tensor_data.size, st.size())
        self.assertEqual(wi.tensor_data.properties, TensorProperties.create_from_tensor(torch.zeros(1)))
        self.assertEqual(wi.tensor_data.chunk.offsets, torch.Size([8]))
        self.assertEqual(wi.tensor_data.chunk.sizes, torch.Size([8]))

        # Coordinator rank, should include replicated items as well
        plan = create_default_local_save_plan(state_dict, True)
        self.assertEqual(3, len(plan.items))

        tensor_wi = next(wi for wi in plan.items if wi.type == WriteItemType.TENSOR)
        self.assertEqual(tensor_wi.index, MetadataIndex("tensor", [0]))
        self.assertEqual(tensor_wi.tensor_data.size, tensor.size())
        self.assertEqual(tensor_wi.tensor_data.properties, TensorProperties.create_from_tensor(tensor))
        self.assertEqual(tensor_wi.tensor_data.chunk.offsets, torch.Size([0]))
        self.assertEqual(tensor_wi.tensor_data.chunk.sizes, torch.Size([10]))

        bytes_wi = next(wi for wi in plan.items if wi.type == WriteItemType.BYTE_IO)
        self.assertEqual(bytes_wi.index, MetadataIndex("value"))
        self.assertIsNone(bytes_wi.tensor_data)

    def test_global_plan(self):
        def create_data(rank):
            with with_dist(rank=rank, world_size=4):
                tensor = torch.rand(10)
                val = [1, 2, 3]
                st = create_sharded_tensor(rank=rank, world_size=4, shards_per_rank=1)
                state_dict = {
                    "tensor": tensor,
                    "value": val,
                    "st": st
                }
                return create_default_local_save_plan(state_dict, rank == 0)

        all_plans = [create_data(0), create_data(1), create_data(2), create_data(3)]
        final_plans, metadata = create_default_global_save_plan(all_plans=all_plans)

        # The default global plan updates all indexes to include hints
        for new_plan, old_plan in zip(final_plans, all_plans):
            for new_item, old_item in zip(new_plan.items, old_plan.items):
                self.assertEqual(new_item.index, old_item.index)
                self.assertEqual(new_item.type, old_item.type)
                self.assertEqual(new_item.tensor_data, old_item.tensor_data)
                self.assertIn(new_item.index.fqn, metadata.state_dict_metadata)

                item_md = metadata.state_dict_metadata[new_item.index.fqn]
                if new_item.type == WriteItemType.BYTE_IO:
                    self.assertTrue(isinstance(item_md, BytesStorageMetadata))
                else:
                    self.assertTrue(isinstance(item_md, TensorStorageMetadata))
                    self.assertEqual(item_md.size, old_item.tensor_data.size)
                    self.assertEqual(item_md.properties, old_item.tensor_data.properties)

                    self.assertIsNotNone(new_item.index.index)
                    # Make sure the hint is correct
                    self.assertEqual(item_md.chunks[new_item.index.index], old_item.tensor_data.chunk)

    def test_local_load_plan(self):
        def create_state_dict(rank):
            with with_dist(rank=rank, world_size=4):
                tensor = torch.rand(10)
                val = [1, 2, 3]
                st = create_sharded_tensor(rank=rank, world_size=4, shards_per_rank=1)
                return {
                    "tensor": tensor,
                    "value": val,
                    "st": st
                }

        state_dict = create_state_dict(1)
        metadata = _create_default_local_metadata(state_dict)

        load_plan = create_default_local_load_plan(state_dict, metadata)
        # This will create 3 entries
        self.assertEqual(3, len(load_plan.items))
        st_item = next(ri for ri in load_plan.items if ri.dest_index.fqn == "st")
        tensor_item = next(ri for ri in load_plan.items if ri.dest_index.fqn == "tensor")
        bytes_item = next(ri for ri in load_plan.items if ri.dest_index.fqn == "value")

        self.assertEqual(st_item.type, LoadItemType.TENSOR)
        # This is an exact copy
        self.assertEqual(st_item.dest_index, MetadataIndex("st", [8]))
        self.assertEqual(st_item.dest_offsets, torch.Size([0]))
        self.assertEqual(st_item.storage_index, MetadataIndex("st", [8]))
        self.assertEqual(st_item.storage_offsets, torch.Size([0]))
        self.assertEqual(st_item.lengths, torch.Size([8]))

        self.assertEqual(tensor_item.type, LoadItemType.TENSOR)
        self.assertEqual(tensor_item.dest_index, MetadataIndex("tensor", [0]))
        self.assertEqual(tensor_item.dest_offsets, torch.Size([0]))
        self.assertEqual(tensor_item.storage_index, MetadataIndex("tensor", [0]))
        self.assertEqual(tensor_item.storage_offsets, torch.Size([0]))
        self.assertEqual(tensor_item.lengths, torch.Size([10]))

        self.assertEqual(bytes_item.type, LoadItemType.BYTE_IO)
        self.assertEqual(bytes_item.dest_index, MetadataIndex("value"))

    def test_load_with_resharding(self):
        def create_state_dict(rank, world_size):
            with with_dist(rank=rank, world_size=world_size):
                return {
                    "st": create_sharded_tensor(
                        rank=rank,
                        world_size=world_size,
                        shards_per_rank=1,
                        shard_size=128 // world_size,
                    )
                }


        # Rank 1 has a 16 bytes shard from [16, 32[
        world8_state_dict = create_state_dict(rank=1, world_size=8)
        world8_metadata = _create_default_local_metadata(world8_state_dict)

        # Rank 1 has a 32 bytes shard from [32, 64[
        world4_state_dict = create_state_dict(rank=1, world_size=4)
        world4_metadata = _create_default_local_metadata(world4_state_dict)

        # First scenario, going from world=8 to world=4, need to load 2 shards
        # Each 4-world shard has 32 elements, so it needs to load 2 shards
        load_plan = create_default_local_load_plan(world4_state_dict, world8_metadata)
        self.assertEqual(2, len(load_plan.items))
        low_ri = next(ri for ri in load_plan.items if ri.dest_offsets == torch.Size([0]))
        high_ri = next(ri for ri in load_plan.items if ri.dest_offsets == torch.Size([16]))

        self.assertEqual(low_ri.storage_index, MetadataIndex("st", [32]))
        self.assertEqual(low_ri.storage_offsets, torch.Size([0]))
        self.assertEqual(low_ri.dest_index, MetadataIndex("st", [32]))
        self.assertEqual(low_ri.dest_offsets, torch.Size([0]))
        self.assertEqual(low_ri.lengths, torch.Size([16]))

        self.assertEqual(high_ri.storage_index, MetadataIndex("st", [48]))
        self.assertEqual(high_ri.storage_offsets, torch.Size([0]))
        self.assertEqual(high_ri.dest_index, MetadataIndex("st", [32]))
        self.assertEqual(high_ri.dest_offsets, torch.Size([16]))
        self.assertEqual(high_ri.lengths, torch.Size([16]))

        # Second scenario, going from world=4 to world=8, need to load half of 1 shard
        # rank1 on 8-world needs to load the upper half of the rank0 4-world shard
        load_plan = create_default_local_load_plan(world8_state_dict, world4_metadata)
        self.assertEqual(1, len(load_plan.items))
        ri = load_plan.items[0]
        self.assertEqual(ri.storage_index, MetadataIndex("st", [0]))
        self.assertEqual(ri.storage_offsets, torch.Size([16]))
        self.assertEqual(ri.dest_index, MetadataIndex("st", [16]))
        self.assertEqual(ri.dest_offsets, torch.Size([0]))
        self.assertEqual(ri.lengths, torch.Size([16]))

    def test_load_with_world_size_diff_by_one(self):
        def create_state_dict(rank, world_size):
            with with_dist(rank=rank, world_size=world_size):
                return {
                    "st": create_sharded_tensor(
                        rank=rank,
                        world_size=world_size,
                        shards_per_rank=1,
                        shard_size=120 // world_size,
                    )
                }
        # rank 1 has a 30 bytes shard from [30, 60[
        world4_state_dict = create_state_dict(rank=1, world_size=4)
        world4_metadata = _create_default_local_metadata(world4_state_dict)

        # rank 1 has a 40 bytes shard from [40, 80[
        world3_state_dict = create_state_dict(rank=1, world_size=3)

        load_plan = create_default_local_load_plan(world3_state_dict, world4_metadata)
        self.assertEqual(2, len(load_plan.items))
        # this is [30, 60] to load [40, 60]
        low_ri = next(ri for ri in load_plan.items if ri.dest_offsets == torch.Size([0]))
        # this is [60, 90] to load [60, 80]
        high_ri = next(ri for ri in load_plan.items if ri.dest_offsets == torch.Size([20]))

        self.assertEqual(low_ri.storage_index, MetadataIndex("st", [30]))
        self.assertEqual(low_ri.storage_offsets, torch.Size([10]))
        self.assertEqual(low_ri.dest_index, MetadataIndex("st", [40]))
        self.assertEqual(low_ri.dest_offsets, torch.Size([0]))
        self.assertEqual(low_ri.lengths, torch.Size([20]))

        self.assertEqual(high_ri.storage_index, MetadataIndex("st", [60]))
        self.assertEqual(high_ri.storage_offsets, torch.Size([0]))
        self.assertEqual(high_ri.dest_index, MetadataIndex("st", [40]))
        self.assertEqual(high_ri.dest_offsets, torch.Size([20]))
        self.assertEqual(high_ri.lengths, torch.Size([20]))

if __name__ == "__main__":
    run_tests()
