from datetime import datetime
import discord

MODALITY_LABELS = {
    "bh_email": "BH Email",
    "personal_email": "Personal Email",
    "bh_text": "BH Text",
    "personal_text": "Personal Text",
    "voice": "Voice",
    "fb_messenger": "FB Messenger",
    "nd_messenger": "ND Messenger",
    "lead_found": "Found Lead",
    "magpie_lead": "Magpie Lead",
}

# Discord's API rejects embed field values of length 0 (min 1, max 1024 chars).
# Use a zero-width space as a round-trip-safe sentinel for "empty" values so we
# never send a literal "" to Discord.
_EMPTY_FIELD_SENTINEL = "​"

# Hard cap for any field value, with headroom for a truncation marker so the
# final value never exceeds Discord's 1024-char limit regardless of caller.
_FIELD_VALUE_MAX = 1024
_TRUNCATION_MARKER = "\n\n[...truncated for Discord embed limit...]"


def _safe_field_value(value: str) -> str:
    """Return a Discord-safe embed field value: never empty, never over 1024 chars."""
    if not value:
        return _EMPTY_FIELD_SENTINEL
    if len(value) > _FIELD_VALUE_MAX:
        keep = _FIELD_VALUE_MAX - len(_TRUNCATION_MARKER)
        return value[:keep] + _TRUNCATION_MARKER
    return value


def build_ping_embed(
    *, modality: str, sender_id: str | None, snippet: str, raw_content: str,
    captured_at: datetime, direction: str = "inbound", image_url: str | None = None,
) -> discord.Embed:
    label = MODALITY_LABELS.get(modality, modality)
    embed = discord.Embed(
        title=f"{label}" + (f" - {sender_id}" if sender_id else ""),
        description=snippet,
    )
    embed.add_field(name="modality", value=_safe_field_value(modality), inline=True)
    embed.add_field(name="direction", value=_safe_field_value(direction), inline=True)
    embed.add_field(name="sender_id", value=_safe_field_value(sender_id or ""), inline=True)
    embed.add_field(
        name="captured_at", value=_safe_field_value(captured_at.isoformat()), inline=True,
    )
    embed.add_field(
        name="raw_content", value=_safe_field_value(raw_content), inline=False,
    )
    # Discord CDN attachment URLs carry a signed expiry (ex/is/hm query params),
    # typically valid ~24h. Fine for same-day triage; a stale link just stops
    # rendering the preview without breaking anything else in the embed.
    if image_url:
        embed.set_image(url=image_url)
    return embed


def parse_ping_embed(embed: discord.Embed) -> dict:
    values = {field.name: field.value for field in embed.fields}
    sender_id = values.get("sender_id")
    if sender_id == _EMPTY_FIELD_SENTINEL:
        sender_id = None
    else:
        sender_id = sender_id or None

    raw_content = values["raw_content"]
    if raw_content == _EMPTY_FIELD_SENTINEL:
        raw_content = ""

    direction = values.get("direction") or "inbound"

    return {
        "modality": values["modality"],
        "sender_id": sender_id,
        "raw_content": raw_content,
        "captured_at": datetime.fromisoformat(values["captured_at"]),
        "direction": direction,
    }