"""Utilities for working with RAML files."""
from functools import reduce
import re


def rule_to_resource_path(rule):
    """Convert a flask route rule to a raml resource path.

    Args:
        rule: rule that matches a request, e.g. /product/<int:product_id>

    Returns:
        str: raml path, e.g. /product/{productId}

    """
    def to_camel_case(snake_str):
        components = snake_str.split('_')
        return components[0] + ''.join(x.title() for x in components[1:])

    return re.sub('<(?:[^:]*:)?([^>]*)>',
                  lambda pat: '{' + to_camel_case(pat.group(1)) + '}',
                  rule)


def find_in_raml(api_definition, rule, method):
    """Find section of raml spec for route rule & method.

    Args:
        api_definition: raml spec to search
        rule: route rule, e.g. /product/<int:product_id>
        method: http method, e.g. "get" or "put"

    Returns:
        RamlSection

    """
    resource_path = rule_to_resource_path(rule)

    resources = ['/{}'.format(s)
                 for s in resource_path.split('/')
                 if s != '']

    resource_method = \
        reduce(lambda resource, s: resource.resources[s],
               resources,
               api_definition).methods[method]
    return RamlSection(resource_method)


def raml_header_to_schema(raml_headers):
    """Convert headers to json schema.

    Takes RAML specs for headers for an endpoint and converts to
    JSON Draft 3 schema to use with our validator
    NOTE: we have to filter out props with None as the value :(

    Args:
        raml_headers (collections.OrderedDict): the headers part of a RAML
            endpoint descriptor.

    Returns:
        dict: the dict representing JSON validation schema snippet.
    """
    properties = {}
    for item in raml_headers:
        _props = raml_headers[item]
        props = {}
        for prop in _props.__dict__:
            if _props.__dict__[prop] is not None:
                props[prop] = _props.__dict__[prop]
        properties[item] = props

    schema = {
        '$schema': 'http://json-schema.org/draft-03/schema',
        'type': 'object',
        'required': True,
        'properties': properties
    }
    return schema


class RamlSection:
    """Section of a RAML api."""

    def __init__(self, api_section):
        """Wrap raml api section."""
        self.api_section = api_section

    def body_schema(self):
        """Schema for json request body."""
        if not self.api_section.body:
            return None

        return self.api_section.body['application/json'].schema

    def header_schema(self):
        """Schema for validating header."""
        return raml_header_to_schema(self.api_section.headers)