from typing import Optional, Tuple

from services.data.db_utils import DBResponse, translate_run_key, translate_task_key, DBPagination, DBResponse
from services.utils import handle_exceptions, web_response
from .utils import format_response_list, get_pathspec_from_request, logger

from aiohttp import web
from multidict import MultiDict


STDOUT = 'log_location_stdout'
STDERR = 'log_location_stderr'


class LogApi(object):
    def __init__(self, app, db, cache=None):
        self.db = db
        app.router.add_route(
            "GET",
            "/flows/{flow_id}/runs/{run_number}/steps/{step_name}/tasks/{task_id}/logs/out",
            self.get_task_log_stdout,
        )
        app.router.add_route(
            "GET",
            "/flows/{flow_id}/runs/{run_number}/steps/{step_name}/tasks/{task_id}/logs/err",
            self.get_task_log_stderr,
        )
        app.router.add_route(
            "GET",
            "/flows/{flow_id}/runs/{run_number}/steps/{step_name}/tasks/{task_id}/logs/out/download",
            self.get_task_log_stdout_file,
        )
        app.router.add_route(
            "GET",
            "/flows/{flow_id}/runs/{run_number}/steps/{step_name}/tasks/{task_id}/logs/err/download",
            self.get_task_log_stderr_file,
        )
        self.metadata_table = self.db.metadata_table_postgres
        self.task_table = self.db.task_table_postgres

        # Cache to hold already fetched logs
        self.cache = getattr(cache, "log_cache", None)

    @handle_exceptions
    async def get_task_log_stdout(self, request):
        """
        ---
        description: Get STDOUT log of a Task
        tags:
        - Task
        parameters:
          - $ref: '#/definitions/Params/Path/flow_id'
          - $ref: '#/definitions/Params/Path/run_number'
          - $ref: '#/definitions/Params/Path/step_name'
          - $ref: '#/definitions/Params/Path/task_id'
          - $ref: '#/definitions/Params/Custom/attempt_id'
        produces:
        - application/json
        responses:
            "200":
                description: Return a tasks stdout log
                schema:
                  $ref: '#/definitions/ResponsesLog'
            "405":
                description: invalid HTTP Method
                schema:
                  $ref: '#/definitions/ResponsesError405'
            "404":
                description: Log for task could not be found
                schema:
                  $ref: '#/definitions/ResponsesError404'
            "500":
                description: Internal Server Error (with error id)
                schema:
                    $ref: '#/definitions/ResponsesLogError500'
        """
        return await self.get_task_log(request, STDOUT)

    @handle_exceptions
    async def get_task_log_stderr(self, request):
        """
        ---
        description: Get STDERR log of a Task
        tags:
        - Task
        parameters:
          - $ref: '#/definitions/Params/Path/flow_id'
          - $ref: '#/definitions/Params/Path/run_number'
          - $ref: '#/definitions/Params/Path/step_name'
          - $ref: '#/definitions/Params/Path/task_id'
          - $ref: '#/definitions/Params/Custom/attempt_id'
        produces:
        - application/json
        responses:
            "200":
                description: Return a tasks stderr log
                schema:
                  $ref: '#/definitions/ResponsesLog'
            "405":
                description: invalid HTTP Method
                schema:
                  $ref: '#/definitions/ResponsesError405'
            "404":
                description: Log for task could not be found
                schema:
                  $ref: '#/definitions/ResponsesError404'
            "500":
                description: Internal Server Error (with error id)
                schema:
                    $ref: '#/definitions/ResponsesLogError500'
        """
        return await self.get_task_log(request, STDERR)

    @handle_exceptions
    async def get_task_log_stdout_file(self, request):
        """
        ---
        description: Get STDOUT log of a Task
        tags:
        - Task
        parameters:
          - $ref: '#/definitions/Params/Path/flow_id'
          - $ref: '#/definitions/Params/Path/run_number'
          - $ref: '#/definitions/Params/Path/step_name'
          - $ref: '#/definitions/Params/Path/task_id'
          - $ref: '#/definitions/Params/Custom/attempt_id'
        produces:
        - text/plain
        responses:
            "200":
                description: Return a tasks stdout log as a file download
            "405":
                description: invalid HTTP Method
                schema:
                  $ref: '#/definitions/ResponsesError405'
            "404":
                description: Log for task could not be found
                schema:
                  $ref: '#/definitions/ResponsesError404'
            "500":
                description: Internal Server Error (with error id)
                schema:
                    $ref: '#/definitions/ResponsesLogError500'
        """
        return await self.get_task_log_file(request, STDOUT)

    @handle_exceptions
    async def get_task_log_stderr_file(self, request):
        """
        ---
        description: Get STDERR log of a Task
        tags:
        - Task
        parameters:
          - $ref: '#/definitions/Params/Path/flow_id'
          - $ref: '#/definitions/Params/Path/run_number'
          - $ref: '#/definitions/Params/Path/step_name'
          - $ref: '#/definitions/Params/Path/task_id'
          - $ref: '#/definitions/Params/Custom/attempt_id'
        produces:
        - text/plain
        responses:
            "200":
                description: Return a tasks stderr log as a file download
            "405":
                description: invalid HTTP Method
                schema:
                  $ref: '#/definitions/ResponsesError405'
            "404":
                description: Log for task could not be found
                schema:
                  $ref: '#/definitions/ResponsesError404'
            "500":
                description: Internal Server Error (with error id)
                schema:
                    $ref: '#/definitions/ResponsesLogError500'
        """
        return await self.get_task_log_file(request, STDERR)

    async def get_task_by_request(self, request):
        flow_id, run_number, step_name, task_id, attempt_id = \
            get_pathspec_from_request(request)

        run_id_key, run_id_value = translate_run_key(run_number)
        task_id_key, task_id_value = translate_task_key(task_id)

        conditions = [
            "flow_id = %s",
            "{run_id_key} = %s".format(run_id_key=run_id_key),
            "step_name = %s",
            "{task_id_key} = %s".format(task_id_key=task_id_key)
        ]
        values = [flow_id, run_id_value, step_name, task_id_value]
        if attempt_id:
            conditions.append("attempt_id = %s")
            values.append(attempt_id)
        # NOTE: Must enable joins so task has attempt_id present for filtering.
        # Log cache action requires a task with an attempt_id,
        # otherwise it defaults to attempt 0
        db_response, *_ = await self.task_table.find_records(
            fetch_single=True,
            conditions=conditions,
            values=values,
            order=["attempt_id DESC"],
            enable_joins=True,
            expanded=True
        )
        if db_response.response_code == 200:
            return db_response.body
        return None

    async def get_task_log(self, request, logtype=STDOUT):
        "fetches log and emits it as a list of rows wrapped in json"
        task = await self.get_task_by_request(request)
        if not task:
            return web_response(404, {'data': []})
        limit, page, reverse_order = get_pagination_params(request)

        lines, page_count = await read_and_output(self.cache, task, logtype, limit, page, reverse_order)

        # paginated response
        response = DBResponse(200, lines)
        pagination = DBPagination(limit, limit * (page - 1), len(response.body), page)
        status, body = format_response_list(request, response, pagination, page, page_count)
        return web_response(status, body)

    async def get_task_log_file(self, request, logtype=STDOUT):
        "fetches log and emits it as a single file download response"
        task = await self.get_task_by_request(request)
        if not task:
            return web_response(404, {'data': []})

        log_filename = "{type}_{flow_id}_{run_number}_{step_name}_{task_id}-{attempt}.txt".format(
            type="stdout" if logtype == STDOUT else "stderr",
            flow_id=task['flow_id'],
            run_number=task['run_number'],
            step_name=task['step_name'],
            task_id=task['task_id'],
            attempt=task['attempt_id']
        )

        def _gen():
            return stream_pages(self.cache, task, logtype, output_raw=True)

        return await file_download_response(request, log_filename, _gen)


async def read_and_output(cache_client, task, logtype, limit=0, page=1, reverse_order=False, output_raw=False):
    res = await cache_client.cache.GetLogFile(task, logtype, limit, page, reverse_order, output_raw, invalidate_cache=True)

    if res.has_pending_request():
        async for event in res.stream():
            if event["type"] == "error":
                # raise error, there was an exception during fetching.
                raise LogException(event["message"], event["id"], event["traceback"])
        await res.wait()  # wait until results are ready

    log_response = res.get()

    if log_response is None:
        # This should not happen under normal circumstances.
        raise LogException("Cache returned None for log content and raised no errors. \
            The cache server might be experiencing issues.")

    return log_response["content"], log_response["pages"]


async def stream_pages(cache_client, task, logtype, output_raw):
    page = 1
    while True:
        logs, _ = await read_and_output(cache_client, task, logtype, limit=1000, page=page, output_raw=output_raw)
        if not logs:
            break
        yield logs
        page += 1


def get_pagination_params(request):
    """extract pagination params from request
    """
    # Page
    page = max(int(request.query.get("_page", 1)), 1)

    # Limit
    # Default limit is 1000, maximum is 10_000
    limit = min(int(request.query.get("_limit", 1000)), 10000)

    # Order
    order = request.query.get("_order")
    reverse_order = order is not None and order.startswith("-row")

    return limit, page, reverse_order


async def file_download_response(request, filename, async_line_iterator):
    response = web.StreamResponse(
        headers=MultiDict({'Content-Disposition': 'Attachment;filename={}'.format(filename)}),
    )
    await response.prepare(request)
    # NOTE: this can not handle errors thrown by the cache, as status cannot be changed after .prepare() has been called.
    async for lines in async_line_iterator():
        await response.write(lines.encode("utf-8"))

    await response.write_eof()
    return response


class LogException(Exception):
    def __init__(self, msg='Failed to read log', id='log-error', traceback_str=None):
        self.message = msg
        self.id = id
        self.traceback_str = traceback_str

    def __str__(self):
        return self.message