"""
Google docstring parser for Python.
"""
from typing import Optional

from litedoc.docstring.docstring import Docstring


class Parser:
    ...


class GoogleDocstringParser(Parser):
    _tokens = {
            "Args"       : "args",
            "Arguments"  : "args",
            "参数"       : "args",

            "Return"     : "return",
            "Returns"    : "return",
            "返回"       : "return",

            "Attribute"  : "attribute",
            "Attributes" : "attribute",
            "属性"       : "attribute",

            "Raises"     : "raises",
            "Raise"      : "raises",
            "引发"       : "raises",

            "Example"    : "example",
            "Examples"   : "example",
            "示例"       : "example",

            "Yields"     : "yields",
            "Yield"      : "yields",
            "产出"       : "yields",

            "Requires"   : "requires",
            "Require"    : "requires",
            "需要"       : "requires",

            "FrontMatter": "front_matter",
            "前言"       : "front_matter",
    }

    def __init__(self, docstring: str, indent: int = 4):
        self.lines = docstring.splitlines()
        self.indent = indent
        self.lineno = 0  # Current line number
        self.char = 0  # Current character position

        self.docstring = Docstring()

    def read_line(self, move: bool = True) -> str:
        """
        每次读取一行
        Args:
            move: 是否移动指针
        Returns:
        """
        if self.lineno >= len(self.lines):
            return ""
        line = self.lines[self.lineno]
        if move:
            self.lineno += 1
        return line

    def match_token(self) -> Optional[str]:
        """
        解析下一行的token
        Returns:

        """
        for token in self._tokens:
            line = self.read_line(move=False)
            if line.strip().startswith(token):
                self.lineno += 1
                return self._tokens[token]
        return None

    def parse_args(self):
        """
        依次解析后面的参数行，直到缩进小于等于当前行的缩进
        """
        while line := self.match_next_line():
            if ":" in line:
                name, desc = line.split(":", 1)
                self.docstring.add_arg(name.strip(), desc.strip())
            else:
                self.docstring.add_arg(line.strip())

    def parse_return(self):
        """
        解析返回值行
        """
        if line := self.match_next_line():
            self.docstring.add_return(line.strip())

    def parse_raises(self):
        """
        解析异常行
        """
        while line := self.match_next_line():
            if ":" in line:
                name, desc = line.split(":", 1)
                self.docstring.add_raise(name.strip(), desc.strip())
            else:
                self.docstring.add_raise(line.strip())

    def parse_example(self):
        """
        解析示例行
        """
        while line := self.match_next_line():
            if ":" in line:
                name, desc = line.split(":", 1)
                self.docstring.add_example(name.strip(), desc.strip())
            else:
                self.docstring.add_example(line.strip())

    def parse_attrs(self):
        """
        解析属性行
        """
        while line := self.match_next_line():
            if ":" in line:
                name, desc = line.split(":", 1)
                self.docstring.add_attrs(name.strip(), desc.strip())
            else:
                self.docstring.add_attrs(line.strip())

    def match_next_line(self) -> Optional[str]:
        """
        在一个子解析器中，解析下一行，直到缩进小于等于当前行的缩进
        Returns:
        """
        line = self.read_line(move=False)
        if line.startswith(" " * self.indent):
            self.lineno += 1
            return line[self.indent:]
        else:
            return None

    def parse(self) -> Docstring:
        """
        逐行解析，直到遇到EOS

        最开始未解析到的内容全部加入desc

        Returns:

        """
        add_desc = True
        while self.lineno < len(self.lines):
            token = self.match_token()
            if token is None and add_desc:
                self.docstring.add_desc(self.lines[self.lineno].strip())

            if token is not None:
                add_desc = False

            match token:
                case "args":
                    self.parse_args()
                case "return":
                    self.parse_return()
                case "attribute":
                    self.parse_attrs()
                case "raises":
                    self.parse_raises()
                case "example":
                    self.parse_example()
                case _:
                    self.lineno += 1

        return self.docstring


class NumpyDocstringParser(Parser):
    ...


class ReStructuredParser(Parser):
    ...


def parse(docstring: str, parser: str = "google", indent: int = 4) -> Docstring:
    if parser == "google":
        return GoogleDocstringParser(docstring, indent).parse()
    else:
        raise ValueError(f"Unknown parser: {parser}")