# 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/.

import json
import sys
from pathlib import Path

import jsonschema
import yaml

HEADER_LINE = (
    "// This file was generated by generate_feature_manifest.py from FeatureManifest.yaml."
    " DO NOT EDIT.\n"
)

FEATURE_MANIFEST_SCHEMA = Path("schemas", "ExperimentFeatureManifest.schema.json")

NIMBUS_FALLBACK_PREFS = (
    "constexpr std::pair<nsLiteralCString, nsLiteralCString>"
    "NIMBUS_FALLBACK_PREFS[]{{{}}};"
)


def write_fm_headers(fd):
    fd.write(HEADER_LINE)


def validate_feature_manifest(schema_path, manifest_path, manifest):
    with open(schema_path, "r") as f:
        schema = json.load(f)

    set_prefs = {}
    fallback_prefs = {}

    for feature, feature_def in manifest.items():
        try:
            jsonschema.validate(feature_def, schema)

            for variable, variable_def in feature_def.get("variables", {}).items():
                set_pref = variable_def.get("setPref")
                if set_pref is not None:
                    if set_pref in set_prefs:
                        other_feature = set_prefs[set_pref][0]
                        other_variable = set_prefs[set_pref][1]
                        print("Multiple variables cannot declare the same setPref")
                        print(
                            f"{feature} variable {variable} wants to set pref {set_pref}"
                        )
                        print(
                            f"{other_feature} variable {other_variable} wants to set pref "
                            f"{set_pref}"
                        )
                        raise Exception("Set prefs are exclusive")

                    set_prefs[set_pref] = (feature, variable)

                fallback_pref = variable_def.get("fallbackPref")
                if fallback_pref is not None:
                    fallback_prefs[fallback_pref] = (feature, variable)

                conflicts = [
                    (
                        "setPref",
                        fallback_pref,
                        "fallbackPref",
                        set_prefs.get(fallback_pref),
                    ),
                    ("fallbackPref", set_pref, "setPref", fallback_prefs.get(set_pref)),
                ]

                for kind, pref, other_kind, conflict in conflicts:
                    if conflict is not None:
                        print(
                            "The same pref cannot be specified in setPref and fallbackPref"
                        )
                        print(
                            f"{feature} variable {variable} has specified {kind} {pref}"
                        )
                        print(
                            f"{conflict[0]} variable {conflict[1]} has specified {other_kind} "
                            f"{pref}"
                        )
                        raise Exception("Set prefs and fallback prefs cannot overlap")

        except Exception as e:
            print("Error while validating FeatureManifest.yaml")
            print(f"On key: {feature}")
            print(f"Input file: {manifest_path}")
            raise e


def generate_feature_manifest(fd, input_file):
    write_fm_headers(fd)

    try:
        with open(input_file, "r", encoding="utf-8") as f:
            manifest = yaml.safe_load(f)

        validate_feature_manifest(
            Path(input_file).parent / FEATURE_MANIFEST_SCHEMA, input_file, manifest
        )

        fd.write(f"export const FeatureManifest = {json.dumps(manifest)};")
    except (IOError) as e:
        print(f"{input_file}: error:\n  {e}\n")
        sys.exit(1)


def platform_feature_manifest_array(features):
    entries = []
    for (feature, featureData) in features.items():
        # Features have to be tagged isEarlyStartup to be accessible
        # to Nimbus platform API
        if not featureData.get("isEarlyStartup", False):
            continue
        entries.extend(
            '{{ "{}_{}"_ns, "{}"_ns }}'.format(
                feature, variable, variableData["fallbackPref"]
            )
            for (variable, variableData) in featureData.get("variables", {}).items()
            if variableData.get("fallbackPref", False)
        )
    return NIMBUS_FALLBACK_PREFS.format(", ".join(entries))


def generate_platform_feature_manifest(fd, input_file):
    write_fm_headers(fd)

    def file_structure(data):
        return "\n".join(
            [
                "#ifndef mozilla_NimbusFeaturesManifest_h",
                "#define mozilla_NimbusFeaturesManifest_h",
                "#include <utility>",
                '#include "mozilla/Maybe.h"',
                '#include "nsStringFwd.h"',
                "namespace mozilla {",
                platform_feature_manifest_array(data),
                '#include "./lib/NimbusFeatureManifest.inc.h"',
                "}  // namespace mozilla",
                "#endif  // mozilla_NimbusFeaturesManifest_h",
            ]
        )

    try:
        with open(input_file, "r", encoding="utf-8") as yaml_input:
            data = yaml.safe_load(yaml_input)
            fd.write(file_structure(data))
    except (IOError) as e:
        print("{}: error:\n  {}\n".format(input_file, e))
        sys.exit(1)