from collections import defaultdict
from typing import Any, Callable, Dict, List, NewType, Union

from sqlalchemy import and_, literal

import aurweb.config as config

from aurweb import db, defaults, models, util
from aurweb.exceptions import RPCError
from aurweb.packages.search import RPCSearch

TYPE_MAPPING = {
    "depends": "Depends",
    "makedepends": "MakeDepends",
    "checkdepends": "CheckDepends",
    "optdepends": "OptDepends",
    "conflicts": "Conflicts",
    "provides": "Provides",
    "replaces": "Replaces",
}

DataGenerator = NewType("DataGenerator",
                        Callable[[models.Package], Dict[str, Any]])


class RPC:
    """ RPC API handler class.

    There are various pieces to RPC's process, and encapsulating them
    inside of a class means that external users do not abuse the
    RPC implementation to achieve goals. We call type handlers
    by taking a reference to the callback named "_handle_{type}_type(...)",
    and if the handler does not exist, we return a not implemented
    error to the API user.

    EXPOSED_VERSIONS holds the set of versions that the API
    officially supports.

    EXPOSED_TYPES holds the set of types that the API officially
    supports.

    ALIASES holds an alias mapping of type -> type strings.

    We should focus on privatizing implementation helpers and
    focusing on performance in the code used.
    """

    # A set of RPC versions supported by this API.
    EXPOSED_VERSIONS = {5}

    # A set of RPC types supported by this API.
    EXPOSED_TYPES = {
        "info", "multiinfo",
        "search", "msearch",
        "suggest", "suggest-pkgbase"
    }

    # A mapping of type aliases.
    TYPE_ALIASES = {"info": "multiinfo"}

    EXPOSED_BYS = {
        "name-desc", "name", "maintainer",
        "depends", "makedepends", "optdepends", "checkdepends"
    }

    # A mapping of by aliases.
    BY_ALIASES = {"name-desc": "nd", "name": "n", "maintainer": "m"}

    def __init__(self, version: int = 0, type: str = None) -> "RPC":
        self.version = version
        self.type = RPC.TYPE_ALIASES.get(type, type)

    def error(self, message: str) -> Dict[str, Any]:
        return {
            "version": self.version,
            "results": [],
            "resultcount": 0,
            "type": "error",
            "error": message
        }

    def _verify_inputs(self, by: str = [], args: List[str] = []) -> None:
        if self.version is None:
            raise RPCError("Please specify an API version.")

        if self.version not in RPC.EXPOSED_VERSIONS:
            raise RPCError("Invalid version specified.")

        if by not in RPC.EXPOSED_BYS:
            raise RPCError("Incorrect by field specified.")

        if self.type is None:
            raise RPCError("No request type/data specified.")

        if self.type not in RPC.EXPOSED_TYPES:
            raise RPCError("Incorrect request type specified.")

    def _enforce_args(self, args: List[str]) -> None:
        if not args:
            raise RPCError("No request type/data specified.")

    def _get_json_data(self, package: models.Package) -> Dict[str, Any]:
        """ Produce dictionary data of one Package that can be JSON-serialized.

        :param package: Package instance
        :returns: JSON-serializable dictionary
        """

        # Produce RPC API compatible Popularity: If zero, it's an integer
        # 0, otherwise, it's formatted to the 6th decimal place.
        pop = package.PackageBase.Popularity
        pop = 0 if not pop else float(util.number_format(pop, 6))

        snapshot_uri = config.get("options", "snapshot_uri")
        data = defaultdict(list)
        data.update({
            "ID": package.ID,
            "Name": package.Name,
            "PackageBaseID": package.PackageBaseID,
            "PackageBase": package.PackageBase.Name,
            # Maintainer should be set following this update if one exists.
            "Maintainer": None,
            "Version": package.Version,
            "Description": package.Description,
            "URL": package.URL,
            "URLPath": snapshot_uri % package.Name,
            "NumVotes": package.PackageBase.NumVotes,
            "Popularity": pop,
            "OutOfDate": package.PackageBase.OutOfDateTS,
            "FirstSubmitted": package.PackageBase.SubmittedTS,
            "LastModified": package.PackageBase.ModifiedTS
        })

        if package.PackageBase.Maintainer is not None:
            # We do have a maintainer: set the Maintainer key.
            data["Maintainer"] = package.PackageBase.Maintainer.Username

        return data

    def _get_info_json_data(self, package: models.Package) -> Dict[str, Any]:
        data = self._get_json_data(package)

        # All info results have _at least_ an empty list of
        # License and Keywords.
        data.update({
            "License": [],
            "Keywords": []
        })

        # If we actually got extra_info records, update data with
        # them for this particular package.
        if self.extra_info:
            data.update(self.extra_info.get(package.ID, {}))

        return data

    def _assemble_json_data(self, packages: List[models.Package],
                            data_generator: DataGenerator) \
            -> List[Dict[str, Any]]:
        """
        Assemble JSON data out of a list of packages.

        :param packages: A list of Package instances or a Package ORM query
        :param data_generator: Generator callable of single-Package JSON data
        """
        output = []
        for pkg in packages:
            db.refresh(pkg)
            output.append(data_generator(pkg))
        return output

    def _handle_multiinfo_type(self, args: List[str] = [], **kwargs) \
            -> List[Dict[str, Any]]:
        self._enforce_args(args)
        args = set(args)

        packages = db.query(models.Package).join(models.PackageBase).filter(
            models.Package.Name.in_(args))
        ids = {pkg.ID for pkg in packages}

        # Aliases for 80-width.
        Package = models.Package
        PackageKeyword = models.PackageKeyword

        subqueries = [
            # PackageDependency
            db.query(
                models.PackageDependency
            ).join(models.DependencyType).filter(
                models.PackageDependency.PackageID.in_(ids)
            ).with_entities(
                models.PackageDependency.PackageID.label("ID"),
                models.DependencyType.Name.label("Type"),
                models.PackageDependency.DepName.label("Name"),
                models.PackageDependency.DepCondition.label("Cond")
            ).distinct().order_by("ID"),

            # PackageRelation
            db.query(
                models.PackageRelation
            ).join(models.RelationType).filter(
                models.PackageRelation.PackageID.in_(ids)
            ).with_entities(
                models.PackageRelation.PackageID.label("ID"),
                models.RelationType.Name.label("Type"),
                models.PackageRelation.RelName.label("Name"),
                models.PackageRelation.RelCondition.label("Cond")
            ).distinct().order_by("ID"),

            # Groups
            db.query(models.PackageGroup).join(
                models.Group,
                and_(models.PackageGroup.GroupID == models.Group.ID,
                     models.PackageGroup.PackageID.in_(ids))
            ).with_entities(
                models.PackageGroup.PackageID.label("ID"),
                literal("Groups").label("Type"),
                models.Group.Name.label("Name"),
                literal(str()).label("Cond")
            ).distinct().order_by("ID"),

            # Licenses
            db.query(models.PackageLicense).join(
                models.License,
                models.PackageLicense.LicenseID == models.License.ID
            ).filter(
                models.PackageLicense.PackageID.in_(ids)
            ).with_entities(
                models.PackageLicense.PackageID.label("ID"),
                literal("License").label("Type"),
                models.License.Name.label("Name"),
                literal(str()).label("Cond")
            ).distinct().order_by("ID"),

            # Keywords
            db.query(models.PackageKeyword).join(
                models.Package,
                and_(Package.PackageBaseID == PackageKeyword.PackageBaseID,
                     Package.ID.in_(ids))
            ).with_entities(
                models.Package.ID.label("ID"),
                literal("Keywords").label("Type"),
                models.PackageKeyword.Keyword.label("Name"),
                literal(str()).label("Cond")
            ).distinct().order_by("ID")
        ]

        # Union all subqueries together.
        query = subqueries[0].union_all(*subqueries[1:])

        # Store our extra information in a class-wise dictionary,
        # which contains package id -> extra info dict mappings.
        self.extra_info = defaultdict(lambda: defaultdict(list))
        for record in query:
            type_ = TYPE_MAPPING.get(record.Type, record.Type)

            name = record.Name
            if record.Cond:
                name += record.Cond

            self.extra_info[record.ID][type_].append(name)

        return self._assemble_json_data(packages, self._get_info_json_data)

    def _handle_search_type(self, by: str = defaults.RPC_SEARCH_BY,
                            args: List[str] = []) -> List[Dict[str, Any]]:
        # If `by` isn't maintainer and we don't have any args, raise an error.
        # In maintainer's case, return all orphans if there are no args,
        # so we need args to pass through to the handler without errors.
        if by != "m" and not len(args):
            raise RPCError("No request type/data specified.")

        arg = args[0] if args else str()
        if by != "m" and len(arg) < 2:
            raise RPCError("Query arg too small.")

        search = RPCSearch()
        search.search_by(by, arg)

        max_results = config.getint("options", "max_rpc_results")
        results = search.results().limit(max_results)
        return self._assemble_json_data(results, self._get_json_data)

    def _handle_msearch_type(self, args: List[str] = [], **kwargs)\
            -> List[Dict[str, Any]]:
        return self._handle_search_type(by="m", args=args)

    def _handle_suggest_type(self, args: List[str] = [], **kwargs)\
            -> List[str]:
        if not args:
            return []

        arg = args[0]
        packages = db.query(models.Package.Name).join(
            models.PackageBase
        ).filter(
            and_(models.PackageBase.PackagerUID.isnot(None),
                 models.Package.Name.like(f"%{arg}%"))
        ).order_by(models.Package.Name.asc()).limit(20)
        return [pkg.Name for pkg in packages]

    def _handle_suggest_pkgbase_type(self, args: List[str] = [], **kwargs)\
            -> List[str]:
        if not args:
            return []

        packages = db.query(models.PackageBase.Name).filter(
            and_(models.PackageBase.PackagerUID.isnot(None),
                 models.PackageBase.Name.like(f"%{args[0]}%"))
        ).order_by(models.PackageBase.Name.asc()).limit(20)
        return [pkg.Name for pkg in packages]

    def _is_suggestion(self) -> bool:
        return self.type.startswith("suggest")

    def _handle_callback(self, by: str, args: List[str])\
            -> Union[List[Dict[str, Any]], List[str]]:
        # Get a handle to our callback and trap an RPCError with
        # an empty list of results based on callback's execution.
        callback = getattr(self, f"_handle_{self.type.replace('-', '_')}_type")
        results = callback(by=by, args=args)
        return results

    def handle(self, by: str = defaults.RPC_SEARCH_BY, args: List[str] = [])\
            -> Union[List[Dict[str, Any]], Dict[str, Any]]:
        """ Request entrypoint. A router should pass v, type and args
        to this function and expect an output dictionary to be returned.

        :param v: RPC version argument
        :param type: RPC type argument
        :param args: Deciphered list of arguments based on arg/arg[] inputs
        """
        # Prepare our output data dictionary with some basic keys.
        data = {"version": self.version, "type": self.type}

        # Run some verification on our given arguments.
        try:
            self._verify_inputs(by=by, args=args)
        except RPCError as exc:
            return self.error(str(exc))

        # Convert by to its aliased value if it has one.
        by = RPC.BY_ALIASES.get(by, by)

        # Process the requested handler.
        try:
            results = self._handle_callback(by, args)
        except RPCError as exc:
            return self.error(str(exc))

        # These types are special: we produce a different kind of
        # successful JSON output: a list of results.
        if self._is_suggestion():
            return results

        # Return JSON output.
        data.update({
            "resultcount": len(results),
            "results": results
        })
        return data