#!/usr/bin/env python


# Finds all tasks and task outputs on the dependency paths from the given downstream task T
# up to the given source/upstream task S (optional). If the upstream task is not given,
# all upstream tasks on all dependency paths of T will be returned.

# Terms:
# if  the execution of Task T depends on the output of task S on a dependency graph,
#  T is called a downstream/sink task, S is called an upstream/source task.

# This is useful and practical way to find all upstream tasks of task T.
# For example suppose you have a daily computation that starts with a task named Daily.
# And suppose you have another task named Aggregate. Daily triggers a few tasks
# which eventually trigger Aggregate. Now, suppose you find a bug in Aggregate.
# You fixed the bug and now you want to rerun it, including all it's upstream deps.
#
# To do that you run:
#      bin/deps.py --module daily_module Aggregate --daily-param1 xxx --upstream-family Daily
#
# This will output all the tasks on the dependency path between Daily and Aggregate. In
# effect, this is how you find all upstream tasks for Aggregate. Now you can delete its
# output and run Aggregate again. Daily will eventually trigget Aggregate and all tasks on
# the way.
#
# The same code here might be used as a CLI tool as well as a python module.
# In python, invoke find_deps(task, upstream_name) to get a set of all task instances on the
# paths between task T and upstream task S. You can then use the task instances to delete their output or
# perform other computation based on that.
#
# Example:
#
# PYTHONPATH=$PYTHONPATH:/path/to/your/luigi/tasks bin/deps.py \
# --module my.tasks  MyDownstreamTask
# --downstream_task_param1 123456
# [--upstream-family MyUpstreamTask]
#

import luigi.interface
from luigi.contrib.ssh import RemoteTarget
from luigi.contrib.postgres import PostgresTarget
from luigi.contrib.s3 import S3Target
from luigi.target import FileSystemTarget
from luigi.task import flatten
from luigi import parameter
import sys
from luigi.cmdline_parser import CmdlineParser
try:
    from collections.abc import Iterable
except ImportError:
    from collections import Iterable


def get_task_requires(task):
    return set(flatten(task.requires()))


def dfs_paths(start_task, goal_task_family, path=None):
    if path is None:
        path = [start_task]
    if start_task.task_family == goal_task_family or goal_task_family is None:
        for item in path:
            yield item
    for next in get_task_requires(start_task) - set(path):
        for t in dfs_paths(next, goal_task_family, path + [next]):
            yield t


class upstream(luigi.task.Config):
    '''
    Used to provide the parameter upstream-family
    '''
    family = parameter.OptionalParameter(default=None)


def find_deps(task, upstream_task_family):
    '''
    Finds all dependencies that start with the given task and have a path
    to upstream_task_family

    Returns all deps on all paths between task and upstream
    '''
    return {t for t in dfs_paths(task, upstream_task_family)}


def find_deps_cli():
    '''
    Finds all tasks on all paths from provided CLI task
    '''
    cmdline_args = sys.argv[1:]
    with CmdlineParser.global_instance(cmdline_args) as cp:
        return find_deps(cp.get_task_obj(), upstream().family)


def get_task_output_description(task_output):
    '''
    Returns a task's output as a string
    '''
    output_description = "n/a"

    if isinstance(task_output, RemoteTarget):
        output_description = "[SSH] {0}:{1}".format(task_output._fs.remote_context.host, task_output.path)
    elif isinstance(task_output, S3Target):
        output_description = "[S3] {0}".format(task_output.path)
    elif isinstance(task_output, FileSystemTarget):
        output_description = "[FileSystem] {0}".format(task_output.path)
    elif isinstance(task_output, PostgresTarget):
        output_description = "[DB] {0}:{1}".format(task_output.host, task_output.table)
    else:
        output_description = "to be determined"

    return output_description


def main():
    deps = find_deps_cli()
    for task in deps:
        task_output = task.output()

        if isinstance(task_output, dict):
            output_descriptions = [get_task_output_description(output) for label, output in task_output.items()]
        elif isinstance(task_output, Iterable):
            output_descriptions = [get_task_output_description(output) for output in task_output]
        else:
            output_descriptions = [get_task_output_description(task_output)]

        print("   TASK: {0}".format(task))
        for desc in output_descriptions:
            print("                       : {0}".format(desc))


if __name__ == '__main__':
    main()