"""
This module contains the TemplateWriterTask, which writes files based on a template file and a
Context using Jinja2's templating engine.
"""

import os

from jinja2 import Environment, FileSystemLoader

from fireworks.core.firework import FiretaskBase
from fireworks.fw_config import TEMPLATE_DIR

__author__ = "Anubhav Jain"
__copyright__ = "Copyright 2013, The Materials Project"
__maintainer__ = "Anubhav Jain"
__email__ = "ajain@lbl.gov"
__date__ = "Aug 08, 2013"


class TemplateWriterTask(FiretaskBase):
    """
    Task to write templated files via Jinja2 library
    Required parameters:
        - template_file: (str) - path to template file
        - context: (dict) - variable replacements for the template file
        - output_file: (str) - output file
    Optional parameters:
        - append: (bool) - append to output file (instead of overwrite)
        - template_dir: (str) - directory in which to find the template file
    """

    _fw_name = "TemplateWriterTask"

    def run_task(self, fw_spec):
        if self.get("use_global_spec"):
            self._load_params(fw_spec)
        else:
            self._load_params(self)

        with open(self.template_file) as f:
            t = Environment(loader=FileSystemLoader(self.template_dir), autoescape=True).from_string(f.read())
            output = t.render(self.context)

            write_mode = "w+" if self.append_file else "w"
            with open(self.output_file, write_mode) as of:
                of.write(output)

    def _load_params(self, d):

        self.context = d["context"]
        self.output_file = d["output_file"]
        self.append_file = d.get("append")  # append to output file?

        if d.get("template_dir"):
            self.template_dir = d["template_dir"]
        elif TEMPLATE_DIR:
            self.template_dir = TEMPLATE_DIR
        else:
            MODULE_DIR = os.path.dirname(os.path.abspath(__file__))
            self.template_dir = os.path.join(MODULE_DIR, "templates")

        self.template_file = os.path.join(self.template_dir, d["template_file"])
        if not os.path.exists(self.template_file):
            raise ValueError(f"TemplateWriterTask could not find a template file at: {self.template_file}")
