"""POV template engine for combat messages."""

import re
from typing import Any


def render_pov(
    template: str,
    viewer: Any | None,
    attacker: Any | None,
    defender: Any | None,
) -> str:
    """Render a combat message template from a specific viewer's POV.

    Args:
        template: Message template with {attacker}, {defender}, and
            contextual tags like {s}, {es}, {y|ies}, {his}, {him}
        viewer: Entity viewing the message (determines "You" vs name)
        attacker: Attacking entity
        defender: Defending entity

    Returns:
        Rendered message with appropriate perspective substitutions

    Contextual tags apply to the most recently mentioned entity:
    - {s} → "" for 2nd person, "s"/"es" for 3rd (smart conjugation)
    - {es} → "" for 2nd person, "es" for 3rd person
    - {y|ies} → left form for 2nd person, right form for 3rd person
    - {his} → "your" for 2nd person, "his" for 3rd person
    - {him} → "you" for 2nd person, "him" for 3rd person
    """
    if not template:
        return template

    # Track whether the last entity mentioned was "You" (2nd person)
    last_was_you = False

    # Pattern to match all tags
    tag_pattern = re.compile(r"\{(attacker|defender|s|es|his|him|[^}]*\|[^}]*)\}")

    # Process template character by character, building result
    result = []
    pos = 0

    for match in tag_pattern.finditer(template):
        # Add text before this tag
        result.append(template[pos : match.start()])

        tag = match.group(0)
        tag_name = match.group(1)

        # Entity tags
        if tag_name in ("attacker", "defender"):
            entity = attacker if tag_name == "attacker" else defender
            if entity is viewer:
                last_was_you = True
                result.append("You")
            else:
                last_was_you = False
                result.append(entity.name if entity else "")

        # Contextual verb conjugation tags
        elif tag == "{s}":
            if last_was_you:
                result.append("")
            else:
                # Check previous character for smart conjugation
                prev_text = "".join(result)
                if prev_text and (
                    prev_text[-1:] in "sxz"
                    or (len(prev_text) >= 2 and prev_text[-2:] in ("ch", "sh"))
                ):
                    result.append("es")
                else:
                    result.append("s")

        elif tag == "{es}":
            result.append("" if last_was_you else "es")

        elif tag == "{his}":
            result.append("your" if last_was_you else "his")

        elif tag == "{him}":
            # Check if "self" follows to form reflexive pronoun
            remaining = template[match.end() :]
            if remaining.startswith("self"):
                result.append("your" if last_was_you else "him")
            else:
                result.append("you" if last_was_you else "him")

        elif "|" in tag:
            # Handle {a|b} pattern
            content = tag[1:-1]  # Strip { and }
            left, right = content.split("|", 1)
            result.append(left if last_was_you else right)

        else:
            result.append(tag)

        pos = match.end()

    # Add remaining text after last tag
    result.append(template[pos:])

    return "".join(result)