#!/usr/bin/python
#
# Software Carpentry Lesson Validator
#
# Check for errors at Software Carpentry lessons.
#
# Usage:
#
#     $ tools/check

import os
import os.path
import re

import yaml

def report_error(file_path, line_number, line, error_message):
    print("Error at line {} of {}:\n\t{}\n{}".format(line_number,
        file_path, line, error_message))

def report_missing(file_path, missing_element):
    print("Error on {}: missing {}".format(file_path, missing_element))

def report_missing_metadata(missing_element):
    print("Error on YAML header: missing {}".format(missing_element))

def report_broken_link(file_path, line_number, link):
    print("Broken link at line {} of {}:\n\tCan't find {}.".format(line_number,
        file_path, link))

def check_yaml(metadata, skip=[]):
    """
    Check if all metadata are present at YAML header.

    :param skip: list of keys to skip check
    """
    metadata_required = ["layout", "title", "minutes"]
    for key in metadata_required:
        if key not in skip and key not in metadata:
            report_missing_metadata(key)

def check_lesson(file_path):
    pass

def check_discussion(file_path):
    pass

def check_index(file_path):
    # State variables
    in_yaml = False
    yaml_metadata = []
    has_prerequisites = False
    has_topics = False
    has_other_resources = False

    # Load file and process it
    with open(file_path, 'r') as lines:
        for line_number, line in enumerate(lines):
            if re.match('---', line):
                in_yaml = not in_yaml
            elif in_yaml:
                yaml_metadata.append(line)
            elif re.match('> ## Prerequisites', line):
                has_prerequisites = True
            elif re.match('## Topics', line):
                has_topics = True
            elif re.match('## Other Resources', line):
                has_other_resources = True
            else:
                # Check if local links are valid
                matches = re.search('\[.*\]\((?P<link>.*)\)', line)
                if matches and not matches.group("link").startswith("http"):
                    link = os.path.join(os.path.dirname(file_path),
                            matches.group("link"))
                    if link.endswith(".html"):
                        link = link.replace("html", "md")
                    if not os.path.exists(link):
                        report_broken_link(file_path, line_number, link)

    # Check YAML
    yaml_metadata = yaml.load('\n'.join(yaml_metadata))
    check_yaml(yaml_metadata, ["minutes"])

    # Check sections
    if not has_prerequisites:
        report_missing(file_path, "Prerequisites")
    if not has_topics:
        report_missing(file_path, "Topics")
    if not has_other_resources:
        report_missing(file_path, "Other Resources")

def check_intructors(file_path):
    pass

def check_motivation(file_path):
    pass

def check_reference(file_path):
    pass

def check_file(file_path):
    if re.search('[0-9]{2}-.*', file_path):
        check_lesson(file_path)
    elif re.search('discussion', file_path):
        check_discussion(file_path)
    elif re.search('index', file_path):
        check_index(file_path)
    elif re.search('instructors', file_path):
        check_intructors(file_path)
    elif re.search("motivation", file_path):
        check_motivation(file_path)
    elif re.search("reference", file_path):
        check_reference(file_path)

def main():
    lessons_file = os.listdir("pages")
    for lesson in lessons_file:
        if lesson.endswith('.md'):
            check_file('pages/{}'.format(lesson))

if __name__ == "__main__":
    main()