"""
dbscheme file generation

`generate(opts, renderer)` will generate a `dbscheme` file out of a `yml` schema file.

Each final class in the schema file will get a corresponding defining DB table with the id and single properties as
columns.
Moreover:
* single properties in non-final classes will also trigger generation of a table with an id reference and all single
  properties as columns
* each optional property will trigger generation of a table with an id reference and the property value as columns
* each repeated property will trigger generation of a table with an id reference, an `int` index and the property value
  as columns
The type hierarchy will be translated to corresponding `union` declarations.
"""
import typing

import inflection

from misc.codegen.lib import schema
from misc.codegen.loaders import schemaloader
from misc.codegen.lib.dbscheme import *

log = logging.getLogger(__name__)


class Error(Exception):
    pass


def dbtype(typename: str, add_or_none_except: typing.Optional[str] = None) -> str:
    """ translate a type to a dbscheme counterpart, using `@lower_underscore` format for classes.
    For class types, appends an underscore followed by `null` if provided
    """
    if typename[0].isupper():
        underscored = inflection.underscore(typename)
        if add_or_none_except is not None and typename != add_or_none_except:
            suffix = "_or_none"
        else:
            suffix = ""
        return f"@{underscored}{suffix}"
    return typename


def cls_to_dbscheme(cls: schema.Class, lookup: typing.Dict[str, schema.Class], add_or_none_except: typing.Optional[str] = None):
    """ Yield all dbscheme entities needed to model class `cls` """
    if cls.synth:
        return
    if cls.derived:
        yield Union(dbtype(cls.name), (dbtype(c) for c in cls.derived if not lookup[c].synth))
    dir = pathlib.Path(cls.group) if cls.group else None
    # output a table specific to a class only if it is a leaf class or it has 1-to-1 properties
    # Leaf classes need a table to bind the `@` ids
    # 1-to-1 properties are added to a class specific table
    # in other cases, separate tables are used for the properties, and a class specific table is unneeded
    if not cls.derived or any(f.is_single and not f.synth for f in cls.properties):
        binding = not cls.derived
        keyset = KeySet(["id"]) if cls.derived else None
        yield Table(
            keyset=keyset,
            name=inflection.tableize(cls.name),
            columns=[
                Column("id", type=dbtype(cls.name), binding=binding),
            ] + [
                Column(f.name, dbtype(f.type, add_or_none_except))
                for f in cls.properties if f.is_single and not f.synth
            ],
            dir=dir,
        )
    # use property-specific tables for 1-to-many and 1-to-at-most-1 properties
    for f in cls.properties:
        overridden_table_name = f.pragmas.get("ql_db_table_name")
        if f.synth:
            continue
        if f.is_unordered:
            yield Table(
                name=overridden_table_name or inflection.tableize(f"{cls.name}_{f.name}"),
                columns=[
                    Column("id", type=dbtype(cls.name)),
                    Column(inflection.singularize(f.name), dbtype(f.type, add_or_none_except)),
                ],
                dir=dir,
            )
        elif f.is_repeated:
            yield Table(
                keyset=KeySet(["id", "index"]),
                name=overridden_table_name or inflection.tableize(f"{cls.name}_{f.name}"),
                columns=[
                    Column("id", type=dbtype(cls.name)),
                    Column("index", type="int"),
                    Column(inflection.singularize(f.name), dbtype(f.type, add_or_none_except)),
                ],
                dir=dir,
            )
        elif f.is_optional:
            yield Table(
                keyset=KeySet(["id"]),
                name=overridden_table_name or inflection.tableize(f"{cls.name}_{f.name}"),
                columns=[
                    Column("id", type=dbtype(cls.name)),
                    Column(f.name, dbtype(f.type, add_or_none_except)),
                ],
                dir=dir,
            )
        elif f.is_predicate:
            yield Table(
                keyset=KeySet(["id"]),
                name=overridden_table_name or inflection.underscore(f"{cls.name}_{f.name}"),
                columns=[
                    Column("id", type=dbtype(cls.name)),
                ],
                dir=dir,
            )


def check_name_conflicts(decls: list[Table | Union]):
    names = set()
    for decl in decls:
        match decl:
            case Table(name=name):
                if name in names:
                    raise Error(f"Duplicate table name: {
                                name}, you can use `@ql.db_table_name` on a property to resolve this")
                names.add(name)


def get_declarations(data: schema.Schema):
    add_or_none_except = data.root_class.name if data.null else None
    declarations = [d for cls in data.classes.values() if not cls.imported for d in cls_to_dbscheme(cls,
                                                                                                    data.classes, add_or_none_except)]
    if data.null:
        property_classes = {
            prop.type for cls in data.classes.values() for prop in cls.properties
            if cls.name != data.null and prop.type and prop.type[0].isupper()
        }
        declarations += [
            Union(dbtype(t, data.null), [dbtype(t), dbtype(data.null)]) for t in sorted(property_classes)
        ]
    check_name_conflicts(declarations)
    return declarations


def get_includes(data: schema.Schema, include_dir: pathlib.Path, root_dir: pathlib.Path):
    includes = []
    for inc in data.includes:
        inc = include_dir / inc
        with open(inc) as inclusion:
            includes.append(SchemeInclude(src=inc.relative_to(root_dir), data=inclusion.read()))
    return includes


def generate(opts, renderer):
    input = opts.schema
    out = opts.dbscheme

    data = schemaloader.load_file(input)

    dbscheme = Scheme(src=input.name,
                      includes=get_includes(data, include_dir=input.parent, root_dir=input.parent),
                      declarations=get_declarations(data))

    renderer.render(dbscheme, out)