"""MAINT-21 tripwire: a test must patch a Controller global where it is read.

The Controller's code lives in app/main.py and in the files split from it
(app/ctl_*.py, app/rows.py). A function reads a module global from its own
file, so `app.main.NAME = fake` changes only the code that is still in
main.py. This file fails when a test or tool still does that:

  1. it patches an `app.main` attribute that main.py's own functions no
     longer read (a stale patch, silently inert), or
  2. it patches an `app.main` attribute that another file also reads (the
     patch reaches only part of the code).

The way to patch is `tools/main_files.py`: `main_files.live.NAME = fake` sets
NAME in every file that reads it and raises when none does.

Part 3 runs the scan on spoilt sources and the patch helper on the real tree.
Read MUTATION.md for the habit this follows.  `python3 test_split_patches.py`
"""

import ast
import glob
import os
import sys

HERE = os.path.dirname(os.path.abspath(__file__))
sys.path.insert(0, HERE)
sys.path.insert(0, os.path.join(HERE, "tools"))
import main_files  # noqa: E402

fails = []
ALIASES = {"m", "M", "main", "app_main", "_main", "_main_mod", "main_mod"}


def check(name, cond):
    print(f"  {'ok  ' if cond else 'FAIL'} {name}")
    if not cond:
        fails.append(name)


def main_aliases(tree):
    """Names bound to the module app.main in one file."""
    al = set()
    for n in ast.walk(tree):
        if isinstance(n, ast.Import):
            al.update(a.asname for a in n.names
                      if a.name == "app.main" and a.asname)
        elif isinstance(n, ast.ImportFrom) and n.module == "app":
            al.update(a.asname or a.name for a in n.names if a.name == "main")
    for n in ast.walk(tree):
        if (isinstance(n, ast.Assign) and isinstance(n.value, ast.Name)
                and n.value.id in al):
            al.update(t.id for t in n.targets if isinstance(t, ast.Name))
        # `for mod in (app_main, homeview): mod.datetime = fake`
        if (isinstance(n, ast.For) and isinstance(n.target, ast.Name)
                and isinstance(n.iter, (ast.Tuple, ast.List))
                and any(isinstance(e, ast.Name) and e.id in al
                        for e in n.iter.elts)):
            al.add(n.target.id)
    return al


def flat(targets):
    """The assignment targets, tuples and lists taken apart."""
    for t in targets:
        if isinstance(t, (ast.Tuple, ast.List)):
            yield from flat(t.elts)
        else:
            yield t


def patches(src):
    """[(line, name)]: every attribute of app.main a file assigns, or hands to
    setattr / a patching helper as `(app.main alias, "name", value)`."""
    tree = ast.parse(src)
    al = main_aliases(tree)
    out = []
    for n in ast.walk(tree):
        targets = []
        if isinstance(n, ast.Assign):
            targets = n.targets
        elif isinstance(n, (ast.AugAssign, ast.AnnAssign)):
            targets = [n.target]
        for t in flat(targets):
            # `app_main.NAME = x`, or `rig.m.NAME = x` where rig did
            # `import app.main as m`
            if isinstance(t, ast.Attribute) and (
                    (isinstance(t.value, ast.Name) and t.value.id in al)
                    or (isinstance(t.value, ast.Attribute)
                        and t.value.attr in ALIASES)):
                out.append((n.lineno, t.attr))
        if (isinstance(n, ast.Call) and len(n.args) >= 3
                and isinstance(n.args[0], ast.Name) and n.args[0].id in al
                and isinstance(n.args[1], ast.Constant)
                and isinstance(n.args[1].value, str)
                and ast.unparse(n.func) != "getattr"):
            out.append((n.lineno, n.args[1].value))
    return out


def problems(src, where="<source>", readers=main_files.reading):
    """Messages for each patch in `src` that the rule above rejects."""
    out = []
    for line, name in patches(src):
        who = readers(name)
        if "main" not in who:
            out.append(f"{where}:{line} patches main.{name}, which main.py "
                       f"does not read" + (f" (read by {who})" if who else ""))
        elif who != ["main"]:
            out.append(f"{where}:{line} patches main.{name}, which "
                       f"{[w for w in who if w != 'main']} also read: use "
                       f"main_files.live.{name}")
    return out


# --------------------------------------------------------------------------- #
print("1. no test and no tool patches a main global the code reads elsewhere")
sites = bad = 0
for path in sorted(glob.glob(os.path.join(HERE, "test_*.py"))
                   + glob.glob(os.path.join(HERE, "tools", "*.py"))):
    if os.path.basename(path) == "test_split_patches.py":
        continue
    with open(path, encoding="utf-8") as fh:
        src = fh.read()
    found = problems(src, os.path.relpath(path, HERE))
    sites += len(patches(src))
    for msg in found:
        print("       " + msg)
    bad += len(found)
check(f"{sites} patches of an app.main attribute found, {bad} stale or partial",
      sites > 0 and bad == 0)

# --------------------------------------------------------------------------- #
print("\n2. the scan is not blind: spoilt sources are caught")
HEAD = "import app.main as m\n"
check("main.<a name nothing reads> is stale",
      len(problems(HEAD + "m.no_such_global_anywhere = 1\n")) == 1)
check("main.datetime is partial (the clock is read in more than one file)"
      if len(main_files.reading("datetime")) > 1 else
      "main.datetime (one reader here, so nothing to catch yet)",
      len(problems(HEAD + "m.datetime = 1\n")) ==
      (1 if len(main_files.reading("datetime")) > 1 else 0))
check("the same through setattr, a helper and an alias",
      len(problems(HEAD + "k = m\nsetattr(k, 'no_such_global_anywhere', 1)\n"
                   "patched(m, 'no_such_global_anywhere', 1)(f)\n")) == 2)
check("a patch through main_files.live is not flagged",
      problems(HEAD + "import main_files\n"
               "main_files.live.datetime = 1\n") == [])
check("a name only main reads may still be patched on main",
      problems(HEAD + "m.load_options = 1\n") == [])

# --------------------------------------------------------------------------- #
print("\n3. main_files.live sets a global in every file that reads it")
import importlib  # noqa: E402

live = main_files.live
for name in ("datetime", "compute", "_mono"):
    readers = main_files.reading(name)
    mods = [importlib.import_module("app." + r) for r in readers]
    before = [getattr(m, name) for m in mods]
    sentinel = object()
    setattr(live, name, sentinel)
    try:
        hit = all(getattr(m, name) is sentinel for m in mods)
        read_back = getattr(live, name) is sentinel
    finally:
        for m, old in zip(mods, before):
            setattr(m, name, old)
    check(f"{name}: set in all {len(mods)} reading file(s) {readers}, and "
          f"read back", bool(mods) and hit and read_back)
try:
    live.no_such_global_anywhere = 1
    raised = False
except AttributeError:
    raised = True
check("a name no file reads raises instead of patching nothing", raised)

print()
if fails:
    print(f"FAILED: {len(fails)}")
    sys.exit(1)
print("all ok")