"""Handles incoming ebs requests, invokes methods, returns responses."""
import json

from moto.core.responses import BaseResponse
from .models import ebs_backends


class EBSResponse(BaseResponse):
    """Handler for EBS requests and responses."""

    @property
    def ebs_backend(self):
        """Return backend instance specific for this region."""
        return ebs_backends[self.region]

    def snapshots(self, request, full_url, headers):
        self.setup_class(request, full_url, headers)
        if request.method == "POST":
            return self.start_snapshot()

    def snapshot_block(self, request, full_url, headers):
        self.setup_class(request, full_url, headers)
        if request.method == "PUT":
            return self.put_snapshot_block(full_url, headers)
        if request.method == "GET":
            return self.get_snapshot_block()

    def snapshot_blocks(self, request, full_url, headers):
        self.setup_class(request, full_url, headers)
        if request.method == "GET":
            return self.list_snapshot_blocks()

    def start_snapshot(self):
        """
        The following parameters are not yet implemented: ParentSnapshotId, ClientToken, Encrypted, KmsKeyArn, Timeout
        """
        params = json.loads(self.body)
        volume_size = params.get("VolumeSize")
        tags = params.get("Tags")
        description = params.get("Description")
        snapshot = self.ebs_backend.start_snapshot(
            volume_size=volume_size,
            tags=tags,
            description=description,
        )
        return 200, {}, json.dumps(snapshot.to_json())

    def complete_snapshot(self, request, full_url, headers):
        """
        The following parameters are not yet supported: ChangedBlocksCount, Checksum, ChecksumAlgorithm, ChecksumAggregationMethod
        """
        self.setup_class(request, full_url, headers)
        snapshot_id = full_url.split("/")[-1]
        status = self.ebs_backend.complete_snapshot(snapshot_id=snapshot_id)
        return 200, {}, json.dumps(status)

    def put_snapshot_block(self, full_url, headers):
        """
        The following parameters are currently not taken into account: DataLength, Progress.
        The Checksum and ChecksumAlgorithm are taken at face-value, but no validation takes place.
        """
        snapshot_id = full_url.split("/")[-3]
        block_index = full_url.split("/")[-1]
        block_data = self.body
        headers = {k.lower(): v for k, v in headers.items()}
        checksum = headers.get("x-amz-checksum")
        checksum_algorithm = headers.get("x-amz-checksum-algorithm")
        data_length = headers.get("x-amz-data-length")
        checksum, checksum_algorithm = self.ebs_backend.put_snapshot_block(
            snapshot_id=snapshot_id,
            block_index=block_index,
            block_data=block_data,
            checksum=checksum,
            checksum_algorithm=checksum_algorithm,
            data_length=data_length,
        )
        return (
            200,
            {
                "x-amz-Checksum": checksum,
                "x-amz-Checksum-Algorithm": checksum_algorithm,
            },
            "{}",
        )

    def get_snapshot_block(self):
        snapshot_id = self.path.split("/")[-3]
        block_index = self.path.split("/")[-1]
        block = self.ebs_backend.get_snapshot_block(
            snapshot_id=snapshot_id,
            block_index=block_index,
        )
        headers = {
            "x-amz-Checksum": block.checksum,
            "x-amz-Checksum-Algorithm": block.checksum_algorithm,
            "x-amz-Data-Length": block.data_length,
        }
        return 200, headers, block.block_data

    def snapshot_changed_blocks(self, request, full_url, headers):
        self.setup_class(request, full_url, headers)
        first_snapshot_id = self._get_params().get("firstSnapshotId")
        second_snapshot_id = self.path.split("/")[-2]
        changed_blocks, snapshot = self.ebs_backend.list_changed_blocks(
            first_snapshot_id=first_snapshot_id,
            second_snapshot_id=second_snapshot_id,
        )
        blocks = [
            {"BlockIndex": idx, "FirstBlockToken": x, "SecondBlockToken": y}
            for idx, (x, y) in changed_blocks.items()
        ]
        return (
            200,
            {},
            json.dumps(
                dict(
                    ChangedBlocks=blocks,
                    VolumeSize=snapshot.volume_size,
                    BlockSize=snapshot.block_size,
                )
            ),
        )

    def list_snapshot_blocks(self):
        """
        The following parameters are not yet implemented: NextToken, MaxResults, StartingBlockIndex
        """
        snapshot_id = self.path.split("/")[-2]
        snapshot = self.ebs_backend.list_snapshot_blocks(
            snapshot_id=snapshot_id,
        )
        blocks = [
            {"BlockIndex": idx, "BlockToken": b.block_token}
            for idx, b in snapshot.blocks.items()
        ]
        return (
            200,
            {},
            json.dumps(
                dict(
                    Blocks=blocks,
                    VolumeSize=snapshot.volume_size,
                    BlockSize=snapshot.block_size,
                )
            ),
        )