"""MAINT-21: the Controller lives in app/main.py and the files split from it.

A test that reads `app/main.py` for a call, a comment or a def reads
`source()` instead; a test that replaces a global that `main` used to read
calls `patch_global()`, which sets it in each file whose code reads it. A name
no file reads is an error: a stale patch cannot pass unnoticed.
"""
import ast
import glob
import importlib
import os
import symtable

APP = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "app")


def files():
    """main.py, rows.py and ctl_*.py, in that order, as bare file names."""
    split = ["rows.py"] + sorted(os.path.basename(p)
                                 for p in glob.glob(os.path.join(APP, "ctl_*.py")))
    return ["main.py"] + [f for f in split
                          if os.path.exists(os.path.join(APP, f))]


def text(name):
    with open(os.path.join(APP, name), encoding="utf-8") as fh:
        return fh.read()


def source():
    """All the files' text, one after the other."""
    return "\n".join(text(f) for f in files())


def tree(src=None):
    """`ast.parse(source())` with every `*Mixin` class folded into
    `Controller`, so `Controller` has all its methods. Positions refer to
    `source()`."""
    src = source() if src is None else src
    mod = ast.parse(src)
    ctl = next(n for n in mod.body
               if isinstance(n, ast.ClassDef) and n.name == "Controller")
    keep = []
    for n in mod.body:
        if isinstance(n, ast.ClassDef) and n.name.endswith("Mixin"):
            ctl.body.extend(n.body)
        else:
            keep.append(n)
    mod.body = keep
    return mod


def _function_reads(table, acc):
    for s in table.get_symbols():
        if (table.get_type() == "function" and s.is_global()
                and s.is_referenced()):
            acc.add(s.get_name())
    for child in table.get_children():
        _function_reads(child, acc)


def reading(name):
    """The bare module names (`main`, `ctl_cycle` ...) whose functions read
    `name` as a global."""
    out = []
    for f in files():
        acc = set()
        _function_reads(symtable.symtable(text(f), f, "exec"), acc)
        if name in acc:
            out.append(f[:-3])
    return out


class _Live:
    """The globals the Controller's code reads, wherever they are read.

    `live.NAME = value` sets NAME in every file whose functions read it;
    `live.NAME` reads it. A name no file reads is an AttributeError, so a
    patch that changes nothing cannot pass unnoticed.
    """

    def __getattr__(self, name):
        mods = reading(name)
        if not mods:
            raise AttributeError(f"no file under app/ reads the global "
                                 f"{name!r}")
        return getattr(importlib.import_module("app." + mods[0]), name)

    def __setattr__(self, name, value):
        mods = reading(name)
        if not mods:
            raise AttributeError(f"no file under app/ reads the global "
                                 f"{name!r}: a patch of it changes nothing")
        for stem in mods:
            setattr(importlib.import_module("app." + stem), name, value)


live = _Live()