TOPICS = (
    "topics (commands): "
    "mod (kick, bankick, tempban, ban, unban, mute, unmute, voice, devoice, op, deop, halfop, dehalfop, lock, unlock), "
    "config (autoop, autovoice, autohalfop, acl, whitelist, blacklist, except, filter, badword, set, config), "
    "track (seen, info, log), "
    "idle (idle, afk), "
    "admin (join, part, chans). "
    "type !help <topic> or !help <cmd> to know more"
)

MOD_TOPIC = "mod: kick, bankick, tempban, ban, unban, mute, unmute, voice, devoice, op, deop, halfop, dehalfop, lock, unlock. type !help <cmd> for usage"
CONFIG_TOPIC = "config: autoop, autovoice, autohalfop, acl, whitelist, blacklist, except, filter, badword, set, config. type !help <cmd> for usage"
TRACK_TOPIC = "track: seen, info, log. type !help <cmd> for usage"
IDLE_TOPIC = "idle: idle, afk. type !help <cmd> for usage"
ADMIN_TOPIC = "admin: join, part, chans. type !help <cmd> for usage"

MOD = {
    "kick":     "kick a user. usage: !kick <nick> [reason]",
    "bankick":  "ban and kick a user. usage: !bankick <nick|mask> [reason]",
    "tempban":  "timed ban and kick. usage: !tempban <nick|mask> <minutes> [reason]",
    "ban":      "ban and kick, or list bans. usage: !ban <nick|mask> [reason] | !ban list",
    "unban":    "remove a ban. usage: !unban <nick|mask>",
    "mute":     "silence a user (+q). usage: !mute <nick|mask>",
    "unmute":   "remove silence (-q). usage: !unmute <nick|mask>",
    "voice":    "give voice. usage: !voice <nick>",
    "devoice":  "remove voice. usage: !devoice <nick>",
    "op":       "give op. usage: !op <nick>",
    "deop":     "remove op. usage: !deop <nick>",
    "halfop":   "give halfop. usage: !halfop <nick>",
    "dehalfop": "remove halfop. usage: !dehalfop <nick>",
    "lock":     "lock the channel. usage: !lock [m|i]  (default: +mi)",
    "unlock":   "unlock the channel. usage: !unlock [m|i]  (default: -mi)",
}

CONFIG = {
    "autoop":     "manage auto-op list for this channel. usage: !autoop <add|del|list> [nick|mask]",
    "autovoice":  "manage auto-voice list for this channel. usage: !autovoice <add|del|list> [nick|mask]",
    "autohalfop": "manage auto-halfop list for this channel. usage: !autohalfop <add|del|list> [nick|mask]",
    "acl":        "manage trusted nicks (global). usage: !acl <add|del|list> [nick]",
    "whitelist":  "manage global protection bypass list. usage: !whitelist <add|del|list> [mask]",
    "blacklist":  "manage global ban list. usage: !blacklist <add|del|list> [nick|mask]",
    "except":     "manage per-channel protection bypass list. usage: !except <add|del|list> [mask]",
    "filter":     "manage regex content filters. usage: !filter <add|del|list> [pattern]  (del uses index from list)",
    "badword":    "manage word block list. usage: !badword <add|del|list> [word]  (del uses index from list)",
    "set":        "set a config key. usage: !set <key> <value>  (in channel: per-channel; in PM: global)",
    "config":     "show channel config. usage: !config [#channel]",
}

TRACK = {
    "seen": "show when a nick was last seen. usage: !seen <nick>",
    "info": "show nick summary. usage: !info <nick>",
    "log":  "show recent events for a nick (ACL/owner only). usage: !log <nick> [limit]",
}

IDLE = {
    "idle": "show idle time or toggle idle checking. usage: !idle <nick> | !idle <on|off>",
    "afk":  "reset your idle timer. usage: !afk",
}

ADMIN = {
    "join":  "join a channel. usage: !join <#channel>",
    "part":  "leave a channel. usage: !part [#channel]",
    "chans": "list channels the bot is in. usage: !chans",
}

_ALL = {**MOD, **CONFIG, **TRACK, **IDLE, **ADMIN}

TOPIC_MAP = {
    "mod":    (MOD_TOPIC,    MOD),
    "config": (CONFIG_TOPIC, CONFIG),
    "track":  (TRACK_TOPIC,  TRACK),
    "idle":   (IDLE_TOPIC,   IDLE),
    "admin":  (ADMIN_TOPIC,  ADMIN),
}


def lookup(args):
    """Return a help string for args (list of strings) or None if not found.

    lookup([])          -> TOPICS
    lookup(["mod"])     -> MOD_TOPIC
    lookup(["kick"])    -> MOD["kick"]
    lookup(["mod","kick"]) -> MOD["kick"]
    """
    if not args:
        return TOPICS
    first = args[0].lower()
    if first in TOPIC_MAP:
        if len(args) == 1:
            return TOPIC_MAP[first][0]
        cmd = args[1].lower()
        return TOPIC_MAP[first][1].get(cmd)
    return _ALL.get(first)