# -*- coding: utf-8 -*-

from __future__ import division

__copyright__ = "Copyright (C) 2014 Andreas Kloeckner"

__license__ = """
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
"""

from django.conf import settings

import re
import datetime
import six

from markdown.extensions import Extension
from markdown.treeprocessors import Treeprocessor

from django.core.urlresolvers import reverse

from django.core.exceptions import ObjectDoesNotExist


# {{{ tools

class Struct(object):
    def __init__(self, entries):
        for name, val in entries.iteritems():
            self.__dict__[name] = dict_to_struct(val)

    def __repr__(self):
        return repr(self.__dict__)


def dict_to_struct(data):
    if isinstance(data, list):
        return [dict_to_struct(d) for d in data]
    elif isinstance(data, dict):
        return Struct(data)
    else:
        return data

# }}}


# {{{ formatting

class LinkFixerTreeprocessor(Treeprocessor):
    def __init__(self, course):
        Treeprocessor.__init__(self)
        self.course = course

    def run(self, root):
        if root.tag == "a" and root.attrib["href"].startswith("flow:"):
            flow_id = root.attrib["href"][5:]
            root.set("href",
                    reverse("course.views.start_flow",
                        args=(self.course.identifier, flow_id)))

        for child in root:
            self.run(child)


class LinkFixerExtension(Extension):
    def __init__(self, course):
        self.course = course
        Extension.__init__(self)

    def extendMarkdown(self, md, md_globals):
        md.treeprocessors["courseflow_link_fixer"] = \
                LinkFixerTreeprocessor(self.course)


def html_body(course, text):
    import markdown
    return markdown.markdown(text,
        extensions=[
            LinkFixerExtension(course)
            ])

# }}}


def get_course_repo(course):
    from os.path import join

    from dulwich.repo import Repo
    return Repo(join(settings.GIT_ROOT, course.identifier))


def get_repo_blob(repo, full_name, commit_sha=None):
    names = full_name.split("/")

    tree_sha = repo[commit_sha].tree
    tree = repo[tree_sha]

    try:
        for name in names[:-1]:
            mode, blob_sha = tree[name.encode()]
            tree = repo[blob_sha]

        mode, blob_sha = tree[names[-1].encode()]
        return repo[blob_sha]
    except KeyError:
        raise ObjectDoesNotExist("resource '%s' not found" % full_name)


def get_yaml_from_repo(repo, full_name, commit_sha):
    from yaml import load
    return dict_to_struct(
            load(get_repo_blob(repo, full_name, commit_sha).data))


DATE_RE_MATCH = re.compile(r"^([0-9]+)\-([01][0-9])\-([0-3][0-9])$")
WEEK_RE_MATCH = re.compile(r"^(start|end)\s+week\s+([0-9]+)$")


def parse_absolute_date_spec(date_spec):
    match = DATE_RE_MATCH.match(date_spec)
    if not match:
        raise ValueError("invalid absolute datespec: %s" % date_spec)

    return datetime.date(
            int(match.group(1)),
            int(match.group(2)),
            int(match.group(3)))


def parse_date_spec(course_desc, date_spec):
    match = DATE_RE_MATCH.match(date_spec)
    if match:
        return datetime.date(
                int(match.group(1)),
                int(match.group(2)),
                int(match.group(3)))

    match = WEEK_RE_MATCH.match(date_spec)
    if match:
        n = int(match.group(2)) - 1
        if match.group(1) == "start":
            return course_desc.first_course_week_start + datetime.timedelta(days=n*7)
        elif match.group(1) == "end":
            return (course_desc.first_course_week_start
                    + datetime.timedelta(days=n*7+6))
        else:
            raise ValueError("invalid datespec: %s" % date_spec)

    raise ValueError("invalid datespec: %s" % date_spec)


def compute_chunk_weight_and_shown(course_desc, chunk, role):
    now = datetime.datetime.now().date()

    for rule in chunk.rules:
        if hasattr(rule, "role"):
            if role != rule.role:
                continue
        if hasattr(rule, "start"):
            start_date = parse_date_spec(course_desc, rule.start)
            if now < start_date:
                continue
        if hasattr(rule, "end"):
            end_date = parse_date_spec(course_desc, rule.end)
            if end_date < now:
                continue

        shown = True
        if hasattr(rule, "shown"):
            shown = rule.shown

        return rule.weight, shown

    return 0


class NoCourseContent(RuntimeError):
    pass


def get_course_desc(repo, commit_sha):
    course_desc = get_yaml_from_repo(repo, "course.yml", commit_sha)

    assert isinstance(course_desc.course_start, datetime.date)
    assert isinstance(course_desc.course_end, datetime.date)

    # a Monday
    course_desc.first_course_week_start = \
            course_desc.course_start - datetime.timedelta(
                    days=course_desc.course_start.weekday())

    return course_desc


def get_processed_course_chunks(course, course_desc, role):
    for chunk in course_desc.chunks:
        chunk.weight, chunk.shown = \
                compute_chunk_weight_and_shown(
                        course_desc, chunk, role)
        chunk.html_content = html_body(course, chunk.content)

    course_desc.chunks.sort(key=lambda chunk: chunk.weight)

    return [mod for mod in course_desc.chunks
            if chunk.shown]


def get_flow(repo, course, flow_id, commit_sha):
    flow = get_yaml_from_repo(repo, "flows/%s.yml" % flow_id, commit_sha)

    flow.description_html = html_body(course, getattr(flow, "description", None))
    return flow


def set_up_flow_visit_page_data(flow_visit, flow):
    from course.models import FlowPageData

    data = None

    ordinal = 0
    for grp in flow.groups:
        for page in grp.pages:
            data = FlowPageData()
            data.flow_visit = flow_visit
            data.ordinal = ordinal
            data.is_last = False
            data.group_id = grp.id
            data.page_id = page.id

            # FIXME Create page data
            data.save()

            ordinal += 1

    return ordinal


def get_flow_page_desc(flow_id, flow, group_id, page_id):
    for grp in flow.groups:
        if grp.id == group_id:
            for page in grp.pages:
                if page.id == page_id:
                    return page

    raise ObjectDoesNotExist("page '%s/%s' in flow '%s'"
            % (group_id, page_id, flow_id))


# {{{ validation

class ValidationError(RuntimeError):
    pass


ID_RE = re.compile(r"^[\w]+$")


def validate_identifier(location, s):
    if not ID_RE.match(s):
        raise ValidationError("%s: invalid identifier '%s'"
                % (location, s))


def validate_struct(location, obj, required_attrs, allowed_attrs):
    """
    :arg required_attrs: an attribute validation list (see below)
    :arg allowed_attrs: an attribute validation list (see below)

    An attribute validation list is a list of elements, where each element is
    either a string (the name of the attribute), in which case the type of each
    attribute is not checked, or a tuple *(name, type)*, where type is valid
    as a second argument to :func:`isinstance`.
    """

    present_attrs = set(name for name in dir(obj) if not name.startswith("_"))

    for required, attr_list in [
            (True, required_attrs),
            (False, allowed_attrs),
            ]:
        for attr_rec in attr_list:
            if isinstance(attr_rec, tuple):
                attr, allowed_types = attr_rec
            else:
                attr = attr_rec
                allowed_types = None

            if attr not in present_attrs:
                if required:
                    raise ValidationError("%s: attribute '%s' missing"
                            % (location, attr))
            else:
                present_attrs.remove(attr)
                val = getattr(obj, attr)

                if not isinstance(val, allowed_types):
                    raise ValidationError("%s: attribute '%s' has "
                            "wrong type: got '%s', expected '%s'"
                            % (location, attr, type(val).__name__,
                            allowed_types))

    if present_attrs:
        raise ValidationError("%s: extraneous attribute(s) '%s'"
                % (location, ",".join(present_attrs)))


datespec_types = (datetime.date, six.string_types)


def validate_chunk_rule(chunk_rule):
    validate_struct(
            "chunk_rule",
            chunk_rule,
            required_attrs=[
                ("weight", int),
                ],
            allowed_attrs=[
                ("start", (str, datetime.date)),
                ("end", (str, datetime.date)),
                ("role", str),
                ("shown", bool),
            ])


def validate_chunk(chunk):
    validate_struct(
            "chunk",
            chunk,
            required_attrs=[
                ("title", str),
                ("id", str),
                ("rules", list),
                ("content", str),
                ],
            allowed_attrs=[]
            )

    for rule in chunk.rules:
        validate_chunk_rule(rule)


def validate_course_desc_struct(course_desc):
    validate_struct(
            "course_desc",
            course_desc,
            required_attrs=[
                ("name", str),
                ("number", str),
                ("run", str),
                ("description", str),
                ("course_start", datetime.date),
                ("course_end", datetime.date),
                ("chunks", list),
                ],
            allowed_attrs=[]
            )

    for chunk in course_desc.chunks:
        validate_chunk(chunk)


# {{{ flow validation

def validate_flow_page(location, page):
    validate_struct(
            location,
            page,
            required_attrs=[
                ("type", str),
                ("id", str),
                ],
            allowed_attrs=[
                ("content", str),
                ("prompt", str),
                ("title", str),
                ("answers", list),
                ("choices", list),
                ("value", (int, float)),
                ]
            )

    validate_identifier(location, page.id)


def validate_flow_group(location, grp):
    validate_struct(
            location,
            grp,
            required_attrs=[
                ("id", str),
                ("pages", list),
                ],
            allowed_attrs=[]
            )

    for i, page in enumerate(grp.pages):
        validate_flow_page("%s, page %d" % (location, i+1), page)

    validate_identifier(location, grp.id)

    # {{{ check page id uniqueness

    page_ids = set()

    for page in grp.pages:
        if page.id in page_ids:
            raise ValidationError("%s: page id '%s' not unique"
                    % (location, page.id))

        page_ids.add(page.id)

    # }}}


def validate_role(location, role):
    from course.models import participation_role

    if role not in [
            participation_role.instructor,
            participation_role.teaching_assistant,
            participation_role.student,
            participation_role.unenrolled,
            ]:
        raise ValidationError("%s: invalid role '%s'"
                % (location, role))


def validate_flow_permission(location, permission):
    from course.models import FLOW_PERMISSION_CHOICES
    if permission not in dict(FLOW_PERMISSION_CHOICES):
        raise ValidationError("%s: invalid flow permission"
                % location)


def validate_flow_access_rule(location, rule):
    validate_struct(
            location,
            rule,
            required_attrs=[
                ("permissions", list),
                ],
            allowed_attrs=[
                ("roles", list),
                ("start", (datetime.date, str)),
                ("end", (datetime.date, str)),
                ("credit_percent", (int, float)),
                ("time_limit", str),
                ("allowed_visit_count", int),
                ]
            )

    for i, perm in enumerate(rule.permissions):
        validate_flow_permission(
                "%s, permission %d" % (location, i+1),
                perm)

    if hasattr(rule, "roles"):
        for i, role in enumerate(rule.roles):
            validate_role(
                    "%s, role %d" % (location, i+1),
                    role)

    # TODO: validate time limit


def validate_flow_desc(location, flow_desc):
    validate_struct(
            location,
            flow_desc,
            required_attrs=[
                ("title", str),
                ("description", str),
                ("groups", list),
                ],
            allowed_attrs=[
                ("access_rules", list),
                ]
            )

    if hasattr(flow_desc, "access_rules"):
        for i, rule in enumerate(flow_desc.access_rules):
            validate_flow_access_rule(
                    "%s, access rule %d" % (location, i+1),
                    rule)

        last_rule = flow_desc.access_rules[-1]
        if (
                hasattr(last_rule, "roles")
                or hasattr(last_rule, "start")
                or hasattr(last_rule, "end")
                ):
            raise ValidationError("%s: last access rule must set default access "
                    "(i.e. have no attributes other than 'permissions')"
                    % location)

    # {{{ check for non-emptiness

    flow_has_page = False
    for i, grp in enumerate(flow_desc.groups):
        group_has_page = False

        for page in grp.pages:
            group_has_page = flow_has_page = True
            break

        if not group_has_page:
            raise ValidationError("%s, group %d ('%d'): no pages found"
                    % (location, i+1, grp.id))

    if not flow_has_page:
        raise ValidationError("%s: no pages found"
                % location)

    # }}}

    # {{{ check group id uniqueness

    group_ids = set()

    for grp in flow_desc.groups:
        if grp.id in group_ids:
            raise ValidationError("%s: group id '%s' not unique"
                    % (location, grp.id))

        group_ids.add(grp.id)

    # }}}

    for i, grp in enumerate(flow_desc.groups):
        validate_flow_group("%s, group %d ('%s')" % (location, i+1, grp.id), grp)

# }}}


def validate_course_content(repo, validate_sha):
    course_desc = get_yaml_from_repo(repo, "course.yml",
            commit_sha=validate_sha)

    validate_course_desc_struct(course_desc)

    flows_tree = get_repo_blob(repo, "flows", validate_sha)

    for entry in flows_tree.items():
        location = "flows/%s" % entry.path
        flow_desc = get_yaml_from_repo(repo, location,
                commit_sha=validate_sha)

        validate_flow_desc(location, flow_desc)

# }}}

# vim: foldmethod=marker