import os
import re
import uuid

import core.postgres as postgres
import core.users as users


DISCORD_PROVIDER = "discord"
DEFAULT_ENROLLMENT_MODE = "allowlist"
_PROVIDER_PATTERN = re.compile(r"^[a-z0-9][a-z0-9_.-]{0,49}$")


def _normalizeProvider(provider):
    provider = provider.strip().lower() if isinstance(provider, str) else ""
    if not _PROVIDER_PATTERN.fullmatch(provider):
        raise ValueError("provider must be a valid provider name")
    return provider


def _normalizeProviderUserID(providerUserID):
    if providerUserID is None:
        raise ValueError("provider user ID is required")
    providerUserID = str(providerUserID).strip()
    if not providerUserID or len(providerUserID) > 255:
        raise ValueError("provider user ID must be between 1 and 255 characters")
    return providerUserID


def _normalizeDisplayName(displayName):
    if displayName is None:
        return None
    if not isinstance(displayName, str):
        raise ValueError("display name must be a string")
    displayName = displayName.strip()
    if not displayName:
        return None
    if len(displayName) > 255:
        raise ValueError("display name must be at most 255 characters")
    return displayName


def getDiscordEnrollmentMode():
    mode = os.getenv("DISCORD_ENROLLMENT_MODE", DEFAULT_ENROLLMENT_MODE)
    mode = mode.strip().lower()
    return "open" if mode == "open" else DEFAULT_ENROLLMENT_MODE


def getDiscordAllowlist():
    configured = os.getenv("DISCORD_ALLOWLIST")
    if configured is None:
        configured = os.getenv("DISCORD_ALLOWED_USER_IDS", "")
    return {
        value
        for value in re.split(r"[\s,]+", configured)
        if value
    }


def isDiscordEnrollmentAllowed(discordID):
    discordID = _normalizeProviderUserID(discordID)
    if getDiscordEnrollmentMode() == "open":
        return True
    return discordID in getDiscordAllowlist()


def getProviderIdentity(provider, providerUserID):
    provider = _normalizeProvider(provider)
    providerUserID = _normalizeProviderUserID(providerUserID)
    return postgres.select_one(
        "provider_identities",
        {"provider": provider, "provider_user_id": providerUserID},
    )


def getUserForIdentity(provider, providerUserID):
    identity = getProviderIdentity(provider, providerUserID)
    if not identity:
        return None
    return users.getUser(identity["user_uuid"])


def listUserIdentities(userUUID):
    return postgres.select("provider_identities", {"user_uuid": userUUID})


def linkProviderIdentity(userUUID, provider, providerUserID, displayName=None):
    if not users.doesUserUUIDExist(userUUID):
        raise ValueError("user does not exist")
    provider = _normalizeProvider(provider)
    providerUserID = _normalizeProviderUserID(providerUserID)
    displayName = _normalizeDisplayName(displayName)

    existing = getProviderIdentity(provider, providerUserID)
    if existing:
        if str(existing["user_uuid"]) != str(userUUID):
            raise ValueError("provider identity is already linked to another user")
        if existing.get("display_name") != displayName:
            updated = postgres.update(
                "provider_identities",
                {"display_name": displayName},
                {"id": existing["id"]},
            )
            return updated[0]
        return existing

    return postgres.insert(
        "provider_identities",
        {
            "id": str(uuid.uuid4()),
            "user_uuid": str(userUUID),
            "provider": provider,
            "provider_user_id": providerUserID,
            "display_name": displayName,
        },
    )


def unlinkProviderIdentity(userUUID, provider, providerUserID):
    provider = _normalizeProvider(provider)
    providerUserID = _normalizeProviderUserID(providerUserID)
    deleted = postgres.delete(
        "provider_identities",
        {
            "user_uuid": userUUID,
            "provider": provider,
            "provider_user_id": providerUserID,
        },
    )
    return bool(deleted)


def linkDiscordIdentity(userUUID, discordID, displayName=None):
    return linkProviderIdentity(
        userUUID,
        DISCORD_PROVIDER,
        discordID,
        displayName=displayName,
    )


def linkDiscordUser(discordID, userUUID=None, username=None, displayName=None):
    if bool(userUUID) == bool(username):
        raise ValueError("provide either user UUID or username")
    if username:
        userUUID = users.getUserUUID(username)
    if not userUUID or not users.doesUserUUIDExist(userUUID):
        raise ValueError("user does not exist")
    return linkDiscordIdentity(userUUID, discordID, displayName=displayName)


def getDiscordUser(discordID):
    return getUserForIdentity(DISCORD_PROVIDER, discordID)


def getOrCreateDiscordUser(discordID, displayName=None, timezoneName=None):
    discordID = _normalizeProviderUserID(discordID)
    displayName = _normalizeDisplayName(displayName)
    if timezoneName is None:
        timezoneName = users.getDefaultTimezone()
    else:
        timezoneName = users.normalizeTimezone(timezoneName)

    existing = getProviderIdentity(DISCORD_PROVIDER, discordID)
    if existing:
        if displayName is not None and existing.get("display_name") != displayName:
            postgres.update(
                "provider_identities",
                {"display_name": displayName},
                {"id": existing["id"]},
            )
        return users.getUser(existing["user_uuid"])
    if not isDiscordEnrollmentAllowed(discordID):
        return None

    with postgres.get_cursor() as cursor:
        cursor.execute(
            "SELECT pg_advisory_xact_lock(hashtext(%(lock_key)s))",
            {"lock_key": f"discord:{discordID}"},
        )
        cursor.execute(
            """
            SELECT users.*
            FROM provider_identities
            JOIN users ON users.id = provider_identities.user_uuid
            WHERE provider = %(provider)s AND provider_user_id = %(provider_user_id)s
            """,
            {
                "provider": DISCORD_PROVIDER,
                "provider_user_id": discordID,
            },
        )
        existingUser = cursor.fetchone()
        if existingUser:
            return dict(existingUser)

        userUUID = str(uuid.uuid4())
        cursor.execute(
            """
            INSERT INTO users (id, username, password_hashed, timezone)
            VALUES (%(id)s, NULL, NULL, %(timezone)s)
            RETURNING *
            """,
            {"id": userUUID, "timezone": timezoneName},
        )
        userRecord = dict(cursor.fetchone())
        cursor.execute(
            """
            INSERT INTO provider_identities (
                id, user_uuid, provider, provider_user_id, display_name
            ) VALUES (
                %(id)s, %(user_uuid)s, %(provider)s,
                %(provider_user_id)s, %(display_name)s
            )
            """,
            {
                "id": str(uuid.uuid4()),
                "user_uuid": userUUID,
                "provider": DISCORD_PROVIDER,
                "provider_user_id": discordID,
                "display_name": displayName,
            },
        )
        return userRecord