"""Plugin: user-defined command aliases (persistent)."""

from __future__ import annotations

import logging

from derp.plugin import command

log = logging.getLogger(__name__)

_NS = "alias"


@command("alias", help="Aliases: !alias add|del|list|clear")
async def cmd_alias(bot, message):
    """Create short aliases for existing bot commands.

    Usage:
        !alias add <name> <target>   Create alias (e.g. !alias add s skip)
        !alias del <name>            Remove alias
        !alias list                  Show all aliases
        !alias clear                 Remove all aliases (admin only)
    """
    parts = message.text.split(None, 3)
    if len(parts) < 2:
        await bot.reply(message, "Usage: !alias <add|del|list|clear> [args]")
        return

    sub = parts[1].lower()

    if sub == "add":
        if len(parts) < 4:
            await bot.reply(message, "Usage: !alias add <name> <target>")
            return
        name = parts[2].lower()
        target = parts[3].lower()

        # Cannot shadow an existing registered command
        if name in bot.registry.commands:
            await bot.reply(message, f"'{name}' is already a registered command")
            return

        # Cannot alias to another alias (single-level only)
        if bot.state.get(_NS, target) is not None:
            await bot.reply(message, f"'{target}' is itself an alias; no chaining")
            return

        # Target must resolve to a real command
        if target not in bot.registry.commands:
            await bot.reply(message, f"unknown command: {target}")
            return

        bot.state.set(_NS, name, target)
        await bot.reply(message, f"alias: {name} -> {target}")

    elif sub == "del":
        if len(parts) < 3:
            await bot.reply(message, "Usage: !alias del <name>")
            return
        name = parts[2].lower()
        if bot.state.delete(_NS, name):
            await bot.reply(message, f"alias removed: {name}")
        else:
            await bot.reply(message, f"no alias: {name}")

    elif sub == "list":
        keys = bot.state.keys(_NS)
        if not keys:
            await bot.reply(message, "No aliases defined")
            return
        entries = []
        for key in sorted(keys):
            target = bot.state.get(_NS, key)
            entries.append(f"{key} -> {target}")
        await bot.reply(message, "Aliases: " + ", ".join(entries))

    elif sub == "clear":
        if not bot._is_admin(message):
            await bot.reply(message, "Permission denied: clear requires admin")
            return
        count = bot.state.clear(_NS)
        await bot.reply(message, f"Cleared {count} alias(es)")

    else:
        await bot.reply(message, "Usage: !alias <add|del|list|clear> [args]")