import glob

class WikiArticle:
    def __init__(self, filename):
        def tags(content):
            for line in content:
                if line.startswith('#+FILETAGS:'):
                    tags = line.replace(' ', '').strip().split(":")[1:]
                    tags = list(filter(identity, tags))
                    return tags
            raise Exception(f'no tags in {filename}')

        def title(content):
            for line in content:
                if line.startswith('#+TITLE:'):
                    res = line.strip().replace(' ', '', 1).split(':')
                    if len(res) > 2: raise Exception(f'Invalid title in {filename}')
                    return res[-1]
            raise Exception(f'No title in {filename}')

        with open(filename, 'r') as f:
            content = f.readlines()
        self.content = [c.strip() for c in content]
        self.title = title(content)
        self.tags = tags(content)
        self.filename = filename
        
    def __repr__(self):
        return f'{type(self).__name__}({self.title}, {self.filename}, {self.tags})'

class ContentArticle(WikiArticle): pass
class MetaPage(WikiArticle):
    def __init__(self, filename):
        self.header = '** Pages in this category'
        super().__init__(filename)
        if len(self.tags) > 1:
            raise Exception(f'Multiple tags in metapage: {self.filename}')
        self.meta = self.tags[0]

        correct_section = list(filter(lambda l: l == self.header, self.content))
        if len(correct_section) != 1:
            raise Exception(f'Invalid meta section in {filename}')

    def replace_content(self, wikiarticles):
        content = map(identity, self.content)
        def rep():
            for line in content:
                if line == self.header: break
                else: yield line
            yield self.header
            for w in wikiarticles:
                yield f'- [[../{w.filename}][{w.title}]]'
        return rep()
                

identity = lambda x: x
def merge(d1, d2):
    d1.update(d2)
    return d1

def files():
    return filter(lambda f: f not in {'todo.org'}, glob.glob('*.org'))

def metafiles():
    return glob.glob('meta/*.org')
    

def invert_map(map_: list[WikiArticle]):
    '''from {a: [1, 2], b: [2, 3]} to {1: [a], 2: [a, b], 3: [b]}'''
    keys = set(i for e in map_ for i in e.tags)
    res = dict()
    for k in keys:
        res[k] = res.get(k, []) + [w for w in map_ if k in w.tags]
    return res

def write_meta_page(m: MetaPage, content: list[str]):
    with open(m.filename, 'w') as f:
        f.writelines(map(lambda l: l+'\n', content))

if __name__ == '__main__':
    files = [ContentArticle(f) for f in files()]
    meta = [MetaPage(f) for f in metafiles()]
    meta = {m.meta: m for m in meta}
    print(meta)
    tags = invert_map(files)
    for t, articles in tags.items():
        if t in meta:
            newcontent = meta[t].replace_content(articles)
            write_meta_page(meta[t], newcontent)