# Copyright 2014 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).

import pprint

import pystache

from pants.base.mustache import MustacheRenderer


# TODO(benjy): Get rid of this class? It just adds complexity, and a regular dict should be fine.
# Unfortunately we first have to fix external uses of this should-be-internal-only class.
class TemplateData(dict):
    """Encapsulates mustache template arguments as a property-addressable read-only object."""

    def __init__(self, **kwargs):
        super().__init__(MustacheRenderer.expand(kwargs))

    def extend(self, **kwargs):
        """Returns a new instance with this instance's data overlayed by the key-value args."""

        props = self.copy()
        props.update(kwargs)
        return TemplateData(**props)

    def __setattr__(self, key, value):
        raise AttributeError(
            "Mutation not allowed - use {}.extend({} = {})".format(self, key, value)
        )

    def __getattr__(self, key):
        if key in self:
            return self[key]
        else:
            return object.__getattribute__(self, key)

    def __str__(self):
        return "TemplateData({})".format(pprint.pformat(self))


# TODO(benjy): Get rid of this class? It adds basically nothing over the MustacheRenderer.
class Generator:
    """Generates pants intermediary output files using a configured mustache template."""

    def __init__(self, template_text, **template_data):
        self._template = MustacheRenderer.parse_template(template_text)
        self.template_data = template_data

    def render(self):
        """Applies the template to the template data and returns the output."""
        return pystache.render(self._template, self.template_data)

    def write(self, stream):
        """Applies the template to the template data and writes the result to the given file-like
        stream."""

        stream.write(self.render())