"""
User persona — manages the optional user identity injected into the prompt.

The persona is a simple dict with five optional string fields:
    name        : the user's character name in the roleplay
    age         : character age
    gender      : character gender
    personality : brief personality description (e.g. "shy but curious")
    background  : brief backstory (e.g. "a journalist investigating the case")

All fields are optional. Blank fields are omitted from the prompt entirely.
Injected into the system prompt via build_persona_prompt() in prompt_builder.py.

UI form is added in Phase 9. This module handles backend logic only.
"""

PERSONA_FIELDS: tuple[str, ...] = ("name", "age", "gender", "personality", "background")


def get_empty_persona() -> dict[str, str]:
    """Return a blank persona dict with all fields set to empty string."""
    return {field: "" for field in PERSONA_FIELDS}


def is_persona_empty(persona: dict[str, str] | None) -> bool:
    """Return True if persona is None or every field is blank."""
    if not persona:
        return True
    return not any(persona.get(field, "").strip() for field in PERSONA_FIELDS)


def validate_persona(raw: dict) -> dict[str, str]:
    """
    Sanitise a persona input dict.
    - Strips whitespace from all values.
    - Fills missing fields with empty string.
    - Ignores unknown fields.
    Returns a clean persona dict guaranteed to have exactly PERSONA_FIELDS keys.
    """
    return {
        field: str(raw.get(field, "")).strip()
        for field in PERSONA_FIELDS
    }


def persona_summary(persona: dict[str, str] | None) -> str:
    """
    Return a compact one-line display string for the UI (Phase 9).

    Examples:
        {"name": "Alex", "age": "28", "gender": ""}  →  "Alex · age 28"
        {}                                            →  ""
    """
    if is_persona_empty(persona):
        return ""

    parts: list[str] = []
    if persona.get("name"):
        parts.append(persona["name"])
    if persona.get("age"):
        parts.append(f"age {persona['age']}")
    if persona.get("gender"):
        parts.append(persona["gender"])

    return " · ".join(parts) if parts else "Custom persona active"