"""Epyoc-style docstring parsing.

.. seealso:: http://epydoc.sourceforge.net/manual-fields.html
"""

import inspect
import re
import typing as T

from .common import Docstring
from .common import DocstringMeta
from .common import DocstringParam
from .common import DocstringRaises
from .common import DocstringReturns
from .common import DocstringStyle
from .common import ParseError
from .common import RenderingStyle


def _clean_str(string: str) -> T.Optional[str]:
    string = string.strip()
    if len(string) > 0:
        return string
    return None


def parse(text: str) -> Docstring:
    """Parse the epydoc-style docstring into its components.

    :returns: parsed docstring
    """
    ret = Docstring(style=DocstringStyle.EPYDOC)
    if not text:
        return ret

    text = inspect.cleandoc(text)
    match = re.search("^@", text, flags=re.M)
    if match:
        desc_chunk = text[: match.start()]
        meta_chunk = text[match.start() :]
    else:
        desc_chunk = text
        meta_chunk = ""

    parts = desc_chunk.split("\n", 1)
    ret.short_description = parts[0] or None
    if len(parts) > 1:
        long_desc_chunk = parts[1] or ""
        ret.blank_after_short_description = long_desc_chunk.startswith("\n")
        ret.blank_after_long_description = long_desc_chunk.endswith("\n\n")
        ret.long_description = long_desc_chunk.strip() or None

    param_pattern = re.compile(r"(param|keyword|type)(\s+[_A-z][_A-z0-9]*\??):")
    raise_pattern = re.compile(r"(raise)(\s+[_A-z][_A-z0-9]*\??)?:")
    return_pattern = re.compile(r"(return|rtype|yield|ytype):")
    meta_pattern = re.compile(r"([_A-z][_A-z0-9]+)((\s+[_A-z][_A-z0-9]*\??)*):")

    # tokenize
    stream: T.List[T.Tuple[str, str, T.List[str], str]] = []
    for match in re.finditer(r"(^@.*?)(?=^@|\Z)", meta_chunk, flags=re.S | re.M):
        chunk = match.group(0)
        if not chunk:
            continue

        param_match = re.search(param_pattern, chunk)
        raise_match = re.search(raise_pattern, chunk)
        return_match = re.search(return_pattern, chunk)
        meta_match = re.search(meta_pattern, chunk)

        match = param_match or raise_match or return_match or meta_match
        if not match:
            raise ParseError(f'Error parsing meta information near "{chunk}".')

        desc_chunk = chunk[match.end() :]
        if param_match:
            base = "param"
            key: str = match.group(1)
            args = [match.group(2).strip()]
        elif raise_match:
            base = "raise"
            key: str = match.group(1)
            args = [] if match.group(2) is None else [match.group(2).strip()]
        elif return_match:
            base = "return"
            key: str = match.group(1)
            args = []
        else:
            base = "meta"
            key: str = match.group(1)
            token = _clean_str(match.group(2).strip())
            args = [] if token is None else re.split(r"\s+", token)

            # Make sure we didn't match some existing keyword in an incorrect
            # way here:
            if key in [
                "param",
                "keyword",
                "type",
                "return",
                "rtype",
                "yield",
                "ytype",
            ]:
                raise ParseError(f'Error parsing meta information near "{chunk}".')

        desc = desc_chunk.strip()
        if "\n" in desc:
            first_line, rest = desc.split("\n", 1)
            desc = first_line + "\n" + inspect.cleandoc(rest)
        stream.append((base, key, args, desc))

    # Combine type_name, arg_name, and description information
    params: T.Dict[str, T.Dict[str, T.Any]] = {}
    for base, key, args, desc in stream:
        if base not in ["param", "return"]:
            continue  # nothing to do

        (arg_name,) = args or ("return",)
        info = params.setdefault(arg_name, {})
        info_key = "type_name" if "type" in key else "description"
        info[info_key] = desc

        if base == "return":
            is_generator = key in {"ytype", "yield"}
            if info.setdefault("is_generator", is_generator) != is_generator:
                raise ParseError(f'Error parsing meta information for "{arg_name}".')

    is_done: T.Dict[str, bool] = {}
    for base, key, args, desc in stream:
        if base == "param" and not is_done.get(args[0], False):
            (arg_name,) = args
            info = params[arg_name]
            type_name = info.get("type_name")

            if type_name and type_name.endswith("?"):
                is_optional = True
                type_name = type_name[:-1]
            else:
                is_optional = False

            match = re.match(r".*defaults to (.+)", desc, flags=re.DOTALL)
            default = match.group(1).rstrip(".") if match else None

            meta_item = DocstringParam(
                args=[key, arg_name],
                description=info.get("description"),
                arg_name=arg_name,
                type_name=type_name,
                is_optional=is_optional,
                default=default,
            )
            is_done[arg_name] = True
        elif base == "return" and not is_done.get("return", False):
            info = params["return"]
            meta_item = DocstringReturns(
                args=[key],
                description=info.get("description"),
                type_name=info.get("type_name"),
                is_generator=info.get("is_generator", False),
            )
            is_done["return"] = True
        elif base == "raise":
            (type_name,) = args or (None,)
            meta_item = DocstringRaises(
                args=[key] + args,
                description=desc,
                type_name=type_name,
            )
        elif base == "meta":
            meta_item = DocstringMeta(
                args=[key] + args,
                description=desc,
            )
        else:
            (key, *_) = args or ("return",)
            assert is_done.get(key, False)
            continue  # don't append

        ret.meta.append(meta_item)

    return ret


def compose(
    docstring: Docstring,
    rendering_style: RenderingStyle = RenderingStyle.COMPACT,
    indent: str = "    ",
) -> str:
    """Render a parsed docstring into docstring text.

    :param docstring: parsed docstring representation
    :param rendering_style: the style to render docstrings
    :param indent: the characters used as indentation in the docstring string
    :returns: docstring text
    """

    def process_desc(desc: T.Optional[str], is_type: bool) -> str:
        if not desc:
            return ""

        if rendering_style == RenderingStyle.EXPANDED or (
            rendering_style == RenderingStyle.CLEAN and not is_type
        ):
            (first, *rest) = desc.splitlines()
            return "\n".join(["\n" + indent + first] + [indent + line for line in rest])

        (first, *rest) = desc.splitlines()
        return "\n".join([" " + first] + [indent + line for line in rest])

    parts: T.List[str] = []
    if docstring.short_description:
        parts.append(docstring.short_description)
    if docstring.blank_after_short_description:
        parts.append("")
    if docstring.long_description:
        parts.append(docstring.long_description)
    if docstring.blank_after_long_description:
        parts.append("")

    for meta in docstring.meta:
        if isinstance(meta, DocstringParam):
            if meta.type_name:
                type_name = f"{meta.type_name}?" if meta.is_optional else meta.type_name
                text = f"@type {meta.arg_name}:"
                text += process_desc(type_name, True)
                parts.append(text)
            text = f"@param {meta.arg_name}:" + process_desc(meta.description, False)
            parts.append(text)
        elif isinstance(meta, DocstringReturns):
            (arg_key, type_key) = ("yield", "ytype") if meta.is_generator else ("return", "rtype")
            if meta.type_name:
                text = f"@{type_key}:" + process_desc(meta.type_name, True)
                parts.append(text)
            if meta.description:
                text = f"@{arg_key}:" + process_desc(meta.description, False)
                parts.append(text)
        elif isinstance(meta, DocstringRaises):
            text = f"@raise {meta.type_name}:" if meta.type_name else "@raise:"
            text += process_desc(meta.description, False)
            parts.append(text)
        else:
            text = f"@{' '.join(meta.args)}:"
            text += process_desc(meta.description, False)
            parts.append(text)
    return "\n".join(parts)
