import json
import logging

from json_delta import diff

_LOGGER = logging.getLogger(__name__)

class ChangeLog:
    def __init__(self, old_report, new_report):
        self.features = []
        self.breaking_changes = []
        self._old_report = old_report
        self._new_report = new_report

    def build_md(self):
        buffer = []
        if self.features:
            buffer.append("**Features**")
            buffer.append("")
            for feature in self.features:
                buffer.append("- "+feature)
            buffer.append("")
        if self.breaking_changes:
            buffer.append("**Breaking changes**")
            buffer.append("")
            for breaking_change in self.breaking_changes:
                buffer.append("- "+breaking_change)
        return "\n".join(buffer).strip()

    @staticmethod
    def _unpack_diff_entry(diff_entry):
        return diff_entry[0], len(diff_entry) == 1

    def operation(self, diff_entry):
        path, is_deletion = self._unpack_diff_entry(diff_entry)

        # Is this a new operation group?
        _, operation_name, *remaining_path = path
        if not remaining_path:
            if is_deletion:
                self.breaking_changes.append(_REMOVE_OPERATION_GROUP.format(operation_name))
            else:
                self.features.append(_ADD_OPERATION_GROUP.format(operation_name))
            return

        _, *remaining_path = remaining_path
        if not remaining_path:
            # Not common, but this means this has changed a lot. Compute the list manually
            old_ops_name = list(self._old_report["operations"][operation_name]["functions"])
            new_ops_name = list(self._new_report["operations"][operation_name]["functions"])
            for removed_function in set(old_ops_name) - set(new_ops_name):
                self.breaking_changes.append(_REMOVE_OPERATION.format(operation_name, removed_function))
            for added_function in set(new_ops_name) - set(old_ops_name):
                self.features.append(_ADD_OPERATION.format(operation_name, added_function))
            return

        # Is this a new operation, inside a known operation group?
        function_name, *remaining_path = remaining_path
        if not remaining_path:
            if is_deletion:
                self.breaking_changes.append(_REMOVE_OPERATION.format(operation_name, function_name))
            else:
                self.features.append(_ADD_OPERATION.format(operation_name, function_name))
            return

        if remaining_path[0] == "metadata":
            # Ignore change in metadata for now, they have no impact
            return

        # So method signaure changed. Be vague for now
        self.breaking_changes.append(_SIGNATURE_CHANGE.format(operation_name, function_name))


    def models(self, diff_entry):
        path, is_deletion = self._unpack_diff_entry(diff_entry)

        # Is this a new model?
        _, mtype, *remaining_path = path
        if not remaining_path:
            # Seen once in Network, because exceptions were added. Bypass
            return
        model_name, *remaining_path = remaining_path
        if not remaining_path:
            # A new model or a model deletion is not very interesting by itself
            # since it usually means that there is a new operation
            #
            # We might miss some discrimanator new sub-classes however
            return

        # That's a model signature change
        if mtype in ["enums", "exceptions"]:
            # Don't change log anything for Enums for now
            return

        _, *remaining_path = remaining_path
        if not remaining_path: # This means massive signature changes, that we don't even try to list them
            self.breaking_changes.append(_MODEL_SIGNATURE_CHANGE.format(model_name))
            return

        # This is a real model
        parameter_name, *remaining_path = remaining_path
        is_required = lambda report, model_name, param_name: report["models"]["models"][model_name]["parameters"][param_name]["properties"]["required"]
        if not remaining_path:
            if is_deletion:
                self.breaking_changes.append(_MODEL_PARAM_DELETE.format(model_name, parameter_name))
            else:
                # This one is tough, if the new parameter is "required",
                # then it's breaking. If not, it's a feature
                if is_required(self._new_report, model_name, parameter_name):
                    self.breaking_changes.append(_MODEL_PARAM_ADD_REQUIRED.format(model_name, parameter_name))
                else:
                    self.features.append(_MODEL_PARAM_ADD.format(model_name, parameter_name))
            return

        # The parameter already exists
        new_is_required = is_required(self._new_report, model_name, parameter_name)
        old_is_required = is_required(self._old_report, model_name, parameter_name)

        if new_is_required and not old_is_required:
            # This shift from optional to required
            self.breaking_changes.append(_MODEL_PARAM_CHANGE_REQUIRED.format(parameter_name, model_name))
            return


## Features
_ADD_OPERATION_GROUP = "Added operation group {}"
_ADD_OPERATION = "Added operation {}.{}"
_MODEL_PARAM_ADD = "Model {} has a new parameter {}"

## Breaking Changes
_REMOVE_OPERATION_GROUP = "Removed operation group {}"
_REMOVE_OPERATION = "Removed operation {}.{}"
_SIGNATURE_CHANGE = "Operation {}.{} has a new signature"
_MODEL_SIGNATURE_CHANGE = "Model {} has a new signature"
_MODEL_PARAM_DELETE = "Model {} no longer has parameter {}"
_MODEL_PARAM_ADD_REQUIRED = "Model {} has a new required parameter {}"
_MODEL_PARAM_CHANGE_REQUIRED = "Parameter {} of model {} is now required"

def build_change_log(old_report, new_report):
    change_log = ChangeLog(old_report, new_report)

    result = diff(old_report, new_report)

    for diff_line in result:
        # Operations
        if diff_line[0][0] == "operations":
            change_log.operation(diff_line)
        else:
            change_log.models(diff_line)

    return change_log

def get_report_from_parameter(input_parameter):
    if ":" in input_parameter:
        package_name, version = input_parameter.split(":")
        from .code_report import main
        result = main(
            package_name,
            version=version if version not in ["pypi", "latest"] else None,
            last_pypi=version == "pypi"
        )
        if not result:
            raise ValueError("Was not able to build a report")
        if len(result) == 1:
            with open(result[0], "r") as fd:
                return json.load(fd)

        raise NotImplementedError("Multi-api changelog not yet implemented")

    with open(input_parameter, "r") as fd:
        return json.load(fd)


if __name__ == "__main__":
    import argparse

    parser = argparse.ArgumentParser(
        description='ChangeLog computation',
    )
    parser.add_argument('base',
                        help='Base. Could be a file path, or <package_name>:<version>. Version can be pypi, latest or a real version')
    parser.add_argument('latest',
                        help='Latest. Could be a file path, or <package_name>:<version>. Version can be pypi, latest or a real version')

    parser.add_argument("--debug",
                        dest="debug", action="store_true",
                        help="Verbosity in DEBUG mode")

    args = parser.parse_args()

    logging.basicConfig(level=logging.DEBUG if args.debug else logging.INFO)

    old_report = get_report_from_parameter(args.base)
    new_report = get_report_from_parameter(args.latest)

    # result = diff(old_report, new_report)
    # with open("result.json", "w") as fd:
    #     json.dump(result, fd)

    change_log = build_change_log(old_report, new_report)
    print(change_log.build_md())