import { useMemo, type RefObject } from "react";
import isAwaitingReply from "../(utils)/is-awaiting-reply";
import Stack from "@moduletrace/twui/layout/Stack";
import type {
    BotMessageWithAttachments,
    BotWithLastMessage,
} from "@/src/types";
import useMessageSelection from "../(hooks)/use-message-selection";
import useThreadScroll from "../(hooks)/use-thread-scroll";
import groupMessages from "../(utils)/group-messages";
import BotThinkingRow from "./bot-thinking-row";
import MessageGroupBlock from "./message-group-block";
import OlderMessagesLoader from "./older-messages-loader";
import QuoteSelectionButton from "./quote-selection-button";
import ScrollToBottomButton from "./scroll-to-bottom-button";

type Props = {
    bot: BotWithLastMessage;
    messages: BotMessageWithAttachments[];
    /**
     * The latest step of the bot's active task, shown while it works.
     */
    progress?: string | null;
    /**
     * The latest step of the reply running here, shown while it thinks.
     */
    reply_progress?: string | null;
    /**
     * The last message is still on its way to the server.
     */
    receiving?: boolean;
    /**
     * This session has an active task.
     */
    has_task?: boolean;
    /**
     * The conversation went on in another session: no reply is due here.
     */
    moved_on?: boolean;
    /**
     * Quotes text selected in a message in the composer.
     */
    onQuote?: (params: { text: string }) => void;
    /**
     * The session's older messages, loaded at the top of the thread.
     */
    older?: {
        has_more: boolean;
        /**
         * The thread reaches the start of its oldest session, which carries
         * on from another one that can be opened above it.
         */
        has_previous?: boolean;
        loading: boolean;
        error?: string;
        loadOlder: () => void;
        loadPrevious?: () => void;
    };
};

/**
 * Bottom-anchored: the stack sits 24px above the composer rule and grows
 * upward. Empty space belongs at the top. New messages announce politely.
 * While the bot works on a reply or a task, a status row sits under the
 * last one. Text selected in a message can be quoted in the composer.
 * Older messages load as it scrolls to the top, and at the start of a
 * session that carries on from another, the earlier one can be opened
 * above it (shown only, never put in the bot's prompt); the reversed column keeps
 * the view where it was as they land above it. The thread follows new
 * messages while it sits at its bottom, stays put while it's scrolled up
 * and then offers a button to get back down.
 */
export default function MessageThread({
    bot,
    messages,
    progress,
    reply_progress,
    receiving,
    has_task,
    moved_on,
    onQuote,
    older,
}: Props) {
    const groups = useMemo(() => groupMessages({ messages }), [messages]);
    const scroll = useThreadScroll({ messages });
    const { selection, clear } = useMessageSelection({ ref: scroll.column_ref });

    return (
        <Stack className="relative grow min-h-0 gap-0! items-stretch">
            <Stack
                componentRef={scroll.column_ref as RefObject<HTMLDivElement>}
                className="grow min-h-0 gap-0! items-stretch overflow-y-auto flex-col-reverse"
                onScroll={scroll.on_scroll}
            >
                <Stack
                    componentRef={scroll.content_ref as RefObject<HTMLDivElement>}
                    role="log"
                    aria-live="polite"
                    aria-label={`Conversation with ${bot.name}`}
                    className="w-full max-w-container mx-auto gap-4! items-stretch px-3 md:px-6 pt-6 pb-6"
                >
                    {older?.has_more ? (
                        <OlderMessagesLoader
                            loading={older.loading}
                            error={older.error}
                            onLoad={older.loadOlder}
                        />
                    ) : older?.has_previous && older.loadPrevious ? (
                        <OlderMessagesLoader
                            loading={older.loading}
                            error={older.error}
                            onLoad={older.loadPrevious}
                            label="Show the previous session"
                            manual
                        />
                    ) : null}
                    {groups.map((group) => (
                        <MessageGroupBlock
                            key={group.key}
                            bot={bot}
                            group={group}
                        />
                    ))}
                    <BotThinkingRow
                        bot={bot}
                        progress={progress}
                        reply_progress={reply_progress}
                        awaiting_reply={
                            !moved_on &&
                            isAwaitingReply({
                                last_message: messages[messages.length - 1],
                                face: bot.face,
                            })
                        }
                        receiving={receiving}
                        has_task={has_task}
                    />
                </Stack>
            </Stack>
            {scroll.jump_visible ? (
                <ScrollToBottomButton onClick={scroll.jump_to_bottom} />
            ) : null}
            {selection && onQuote ? (
                <QuoteSelectionButton
                    selection={selection}
                    onQuote={() => {
                        onQuote({ text: selection.text });
                        clear();
                    }}
                />
            ) : null}
        </Stack>
    );
}