"""
Shared notation parsing utilities for PSI2.

Parses Einstein-like notation strings (e.g. "rgb0,c01->rgb1") into
structured element dicts with modality class references via GlobalRegistry.
"""

from __future__ import annotations

import re
from dataclasses import dataclass
from typing import List, Dict, Set, Tuple, Any, Type, Union

from .modalities import (
    GlobalRegistry, SerializableModality, NodeModality, EdgeModality,
)


@dataclass
class ParsedNotation:
    name: str
    modalities: Set[Type[SerializableModality]]
    nodes: Dict[Type[SerializableModality], List[int]]
    edges: Dict[Type[SerializableModality], Union[List[int], List[Tuple[int, int]]]]
    elements: List[Tuple[Type[SerializableModality], Union[int, Tuple[int, int]]]]
    element_names: List[str]


def parse_element(element_str: str) -> Dict[str, Any]:
    """
    Parse a single element string.

    Format examples:
        rgb0 -> RGB frame at index 0
        f01  -> Flow from frame 0 to frame 1
        d0   -> Disparity at frame 0
        c01  -> Camera pose from frame 0 to frame 1

    Returns:
        Dict with keys: modality, modality_cls, indices, raw
    """
    modality_name = re.match(r'^[^0-9]*', element_str)
    if not modality_name:
        raise ValueError(f"Invalid element string: {element_str}")
    modality_name = modality_name.group()

    modality_cls = GlobalRegistry.get(modality_name)
    if modality_cls is None:
        raise ValueError(f"Unknown modality: {element_str} (valid names: {GlobalRegistry.names_str()})")

    times_str = element_str.removeprefix(modality_name)
    if times_str and not times_str.isdigit():
        match = re.match(r"^(\d+)(.+)$", times_str)
        if match:
            digits, trailing = match.groups()
            raise ValueError(
                f"Invalid element '{element_str}': time indices for '{modality_name}' must be digits only. "
                f"Did you mean '{modality_name}{digits},{trailing}'?"
            )
        raise ValueError(
            f"Invalid element '{element_str}': time indices for '{modality_name}' must be digits only."
        )

    times = [x for x in times_str]

    if issubclass(modality_cls, NodeModality):
        if len(times) != 1:
            raise ValueError(f"{modality_name} is a Node and expects 1 time index: {element_str}")
    elif issubclass(modality_cls, EdgeModality):
        if len(times) != 2:
            raise ValueError(f"{modality_name} is an Edge and expects 2 time indices: {element_str}")
    else:
        if times != ['']:
            raise ValueError(
                f"{modality_name} does not take time indices, but got {times}: {element_str}"
            )

    if times != ['']:
        times = list(map(int, times))
    else:
        times = []

    return {"modality": modality_name, "modality_cls": modality_cls, "indices": times, "raw": element_str}


def parse_notation(notation: str) -> List[Dict[str, Any]]:
    """Parse a notation string into a list of element dictionaries."""
    elements = []
    for part in notation.split(","):
        part = part.strip()
        if not part:
            continue
        elements.append(parse_element(part))
    return elements


def analyze_notation(name: str, elements: List[Dict[str, Any]]) -> ParsedNotation:
    """Analyze parsed notation elements to determine requirements."""
    nodes = {}
    edges = {}
    out_elements = []
    for e in elements:
        modality_cls, indices = e['modality_cls'], e['indices']
        if len(indices) == 2:
            edges.setdefault(modality_cls, set()).add(tuple(indices))
            out_elements.append((modality_cls, tuple(indices)))
        elif len(indices) == 1:
            nodes.setdefault(modality_cls, set()).add(indices[0])
            out_elements.append((modality_cls, indices[0]))
        else:
            out_elements.append((modality_cls, 0))
    return ParsedNotation(
        name=name,
        modalities=set(e['modality_cls'] for e in elements),
        nodes={k: list(v) for k, v in nodes.items()},
        edges={k: list(v) for k, v in edges.items()},
        elements=out_elements,
        element_names=[e['raw'] for e in elements],
    )


def parse_full_notation(notation: str) -> Tuple[List[Dict], List[Dict], ParsedNotation, ParsedNotation]:
    """
    Parse full notation with input/output split on '->'.

    Returns:
        input_elements: List of parsed element dicts
        output_elements: List of parsed element dicts
        input_analysis: ParsedNotation for inputs
        output_analysis: ParsedNotation for outputs
    """
    if "->" not in notation:
        raise ValueError(f"Notation must contain '->' to separate inputs from outputs: {notation}")

    input_str, output_str = notation.split("->", 1)

    input_elements = parse_notation(input_str)
    output_elements = parse_notation(output_str)

    if not output_elements:
        raise ValueError(f"No output elements specified in notation: {notation}")

    input_analysis = analyze_notation("input", input_elements)
    output_analysis = analyze_notation("output", output_elements)

    return input_elements, output_elements, input_analysis, output_analysis