# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

"""
Use pywatchman to watch source directories and perform partial
``mach build faster`` builds.
"""

import datetime
import functools
import sys
import time

import mozpack.path as mozpath

# Watchman integration cribbed entirely from
# https://github.com/facebook/watchman/blob/19aebfebb0b5b0b5174b3914a879370ffc5dac37/python/bin/watchman-wait
import pywatchman
from mozpack.copier import FileCopier
from mozpack.manifests import InstallManifest

from mozbuild.backend import get_backend_class


def print_line(prefix, m, now=None):
    now = now or datetime.datetime.utcnow()
    print("[%s %sZ] %s" % (prefix, now.isoformat(), m))


def print_copy_result(elapsed, destdir, result, verbose=True):
    COMPLETE = (
        "Elapsed: {elapsed:.2f}s; From {dest}: Kept {existing} existing; "
        "Added/updated {updated}; "
        "Removed {rm_files} files and {rm_dirs} directories."
    )

    print_line(
        "watch",
        COMPLETE.format(
            elapsed=elapsed,
            dest=destdir,
            existing=result.existing_files_count,
            updated=result.updated_files_count,
            rm_files=result.removed_files_count,
            rm_dirs=result.removed_directories_count,
        ),
    )


class FasterBuildException(Exception):
    def __init__(self, message, cause):
        Exception.__init__(self, message)
        self.cause = cause


class FasterBuildChange:
    def __init__(self):
        self.unrecognized = set()
        self.input_to_outputs = {}
        self.output_to_inputs = {}


class Daemon:
    def __init__(self, config_environment):
        self.config_environment = config_environment
        self._client = None

    @property
    def defines(self):
        defines = dict(self.config_environment.acdefines)
        # These additions work around warts in the build system: see
        # http://searchfox.org/mozilla-central/rev/ad093e98f42338effe2e2513e26c3a311dd96422/config/faster/rules.mk#92-93
        defines.update({
            "AB_CD": "en-US",
        })
        return defines

    @functools.cached_property
    def file_copier(self):
        # TODO: invalidate the file copier when the build system
        # itself changes, i.e., the underlying unified manifest
        # changes.
        file_copier = FileCopier()

        unified_manifest = InstallManifest(
            mozpath.join(
                self.config_environment.topobjdir, "faster", "unified_install_dist_bin"
            )
        )

        unified_manifest.populate_registry(file_copier, defines_override=self.defines)

        return file_copier

    def subscribe_to_topsrcdir(self):
        self.subscribe_to_dir("topsrcdir", self.config_environment.topsrcdir)

    def subscribe_to_dir(self, name, dir_to_watch):
        query = {
            "empty_on_fresh_instance": True,
            "expression": [
                "allof",
                ["type", "f"],
                [
                    "not",
                    [
                        "anyof",
                        ["dirname", ".hg"],
                        ["name", ".hg", "wholename"],
                        ["dirname", ".git"],
                        ["name", ".git", "wholename"],
                    ],
                ],
            ],
            "fields": ["name"],
        }
        watch = self.client.query("watch-project", dir_to_watch)
        if "warning" in watch:
            print("WARNING: ", watch["warning"], file=sys.stderr)

        root = watch["watch"]
        if "relative_path" in watch:
            query["relative_root"] = watch["relative_path"]

        # Get the initial clock value so that we only get updates.
        # Wait 30s to allow for slow Windows IO.  See
        # https://facebook.github.io/watchman/docs/cmd/clock.html.
        query["since"] = self.client.query("clock", root, {"sync_timeout": 30000})[
            "clock"
        ]

        return self.client.query("subscribe", root, name, query)

    def changed_files(self):
        # In theory we can parse just the result variable here, but
        # the client object will accumulate all subscription results
        # over time, so we ask it to remove and return those values.
        files = set()

        data = self.client.getSubscription("topsrcdir")
        if data:
            for dat in data:
                files |= set([
                    mozpath.normpath(mozpath.join(self.config_environment.topsrcdir, f))
                    for f in dat.get("files", [])
                ])

        return files

    def incremental_copy(self, copier, force=False, verbose=True):
        # Just like the 'repackage' target in browser/app/Makefile.in.
        if "cocoa" == self.config_environment.substs["MOZ_WIDGET_TOOLKIT"]:
            bundledir = mozpath.join(
                self.config_environment.topobjdir,
                "dist",
                self.config_environment.substs["MOZ_MACBUNDLE_NAME"],
                "Contents",
                "Resources",
            )
            start = time.monotonic()
            result = copier.copy(
                bundledir,
                skip_if_older=not force,
                remove_unaccounted=False,
                remove_all_directory_symlinks=False,
                remove_empty_directories=False,
            )
            print_copy_result(
                time.monotonic() - start, bundledir, result, verbose=verbose
            )

        destdir = mozpath.join(self.config_environment.topobjdir, "dist", "bin")
        start = time.monotonic()
        result = copier.copy(
            destdir,
            skip_if_older=not force,
            remove_unaccounted=False,
            remove_all_directory_symlinks=False,
            remove_empty_directories=False,
        )
        print_copy_result(time.monotonic() - start, destdir, result, verbose=verbose)

    def input_changes(self, verbose=True):
        """
        Return an iterator of `FasterBuildChange` instances as inputs
        to the faster build system change.
        """

        # TODO: provide the debug diagnostics we want: this print is
        # not immediately before the watch.
        if verbose:
            print_line("watch", "Connecting to watchman")
        # TODO: figure out why a large timeout is required for the
        # client, and a robust strategy for retrying timed out
        # requests.
        self.client = pywatchman.client(timeout=5.0)

        try:
            if verbose:
                print_line("watch", "Checking watchman capabilities")
            # TODO: restrict these capabilities to the minimal set.
            self.client.capabilityCheck(
                required=[
                    "clock-sync-timeout",
                    "cmd-watch-project",
                    "term-dirname",
                    "wildmatch",
                ]
            )

            if verbose:
                print_line(
                    "watch",
                    f"Subscribing to {self.config_environment.topsrcdir}",
                )
            self.subscribe_to_topsrcdir()
            if verbose:
                print_line("watch", f"Watching {self.config_environment.topsrcdir}")

            input_to_outputs = self.file_copier.input_to_outputs_tree()
            for input, outputs in input_to_outputs.items():
                if not outputs:
                    raise Exception(
                        f"Refusing to watch input ({input}) with no outputs"
                    )

            while True:
                try:
                    self.client.receive()

                    changed = self.changed_files()
                    if not changed:
                        continue

                    result = FasterBuildChange()

                    for change in changed:
                        if change in input_to_outputs:
                            result.input_to_outputs[change] = set(
                                input_to_outputs[change]
                            )
                        else:
                            result.unrecognized.add(change)

                    for input, outputs in result.input_to_outputs.items():
                        for output in outputs:
                            if output not in result.output_to_inputs:
                                result.output_to_inputs[output] = set()
                            result.output_to_inputs[output].add(input)

                    yield result

                except pywatchman.SocketTimeout:
                    # Let's check to see if we're still functional.
                    self.client.query("version")

        except pywatchman.CommandError as e:
            # Abstract away pywatchman errors.
            raise FasterBuildException(
                e,
                f"Command error using pywatchman to watch {self.config_environment.topsrcdir}",
            )

        except pywatchman.SocketTimeout as e:
            # Abstract away pywatchman errors.
            raise FasterBuildException(
                e,
                f"Socket timeout using pywatchman to watch {self.config_environment.topsrcdir}",
            )

        finally:
            self.client.close()

    def output_changes(self, verbose=True):
        """
        Return an iterator of `FasterBuildChange` instances as outputs
        from the faster build system are updated.
        """
        for change in self.input_changes(verbose=verbose):
            now = datetime.datetime.utcnow()

            for unrecognized in sorted(change.unrecognized):
                print_line("watch", f"! {unrecognized}", now=now)

            all_outputs = set()
            for input in sorted(change.input_to_outputs):
                outputs = change.input_to_outputs[input]

                print_line("watch", f"< {input}", now=now)
                for output in sorted(outputs):
                    print_line("watch", f"> {output}", now=now)
                all_outputs |= outputs

            if all_outputs:
                partial_copier = FileCopier()
                for output in all_outputs:
                    partial_copier.add(output, self.file_copier[output])

                self.incremental_copy(partial_copier, force=True, verbose=verbose)
                yield change

    def watch(self, verbose=True):
        try:
            active_backend = self.config_environment.substs.get(
                "BUILD_BACKENDS", [None]
            )[0]
            if active_backend:
                backend_cls = get_backend_class(active_backend)(self.config_environment)
        except Exception:
            backend_cls = None

        for change in self.output_changes(verbose=verbose):
            # Try to run the active build backend's post-build step, if possible.
            if backend_cls:
                backend_cls.post_build(self.config_environment, None, 1, False, 0)
