// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

/**
 * INTERNAL LIBRARY
 */

import { addToSet } from "./collections.js";
import { Batch } from "./common.js";
import {
    DateRange,
    IConversation,
    IMessage,
    IMessageCollection,
    IMessageMetadata,
    MessageOrdinal,
    ScoredMessageOrdinal,
    TextLocation,
    TextRange,
} from "./interfaces.js";
import { getBatchesFromCollection } from "./storage.js";

/**
 * Returns the text range represented by a message (and an optional chunk ordinal)
 * @param messageOrdinal
 * @param chunkOrdinal
 * @returns {TextRange}
 */
export function textRangeFromMessageChunk(
    messageOrdinal: MessageOrdinal,
    chunkOrdinal = 0,
): TextRange {
    return {
        start: { messageOrdinal: messageOrdinal, chunkOrdinal: chunkOrdinal },
        end: undefined,
    };
}

export function textRangeFromMessageRange(
    start: MessageOrdinal,
    end: MessageOrdinal,
): TextRange {
    if (start === end) {
        // Point location
        return { start: { messageOrdinal: start } };
    } else if (start < end) {
        return {
            start: { messageOrdinal: start },
            end: { messageOrdinal: end },
        };
    } else {
        throw new Error(`Expect message ordinal range: ${start} <= ${end}`);
    }
}

/**
 * Get the total number of a characters in a message.
 * A message can contain multiple text chunks
 * @param {IMessage} message
 * @returns
 */
export function getMessageCharCount(message: IMessage): number {
    let total = 0;
    for (let i = 0; i < message.textChunks.length; ++i) {
        total += message.textChunks[i].length;
    }
    return total;
}

export function getCharCountOfMessages(messages: Iterable<IMessage>) {
    let total = 0;
    for (const message of messages) {
        total += getMessageCharCount(message);
    }
    return total;
}

/**
 * Given a set of message ordinals, returns the count of messages whose cumulative
 * text length is < than the given character budget
 * @param messages messageOrdinals reference messages in this collection
 * @param messageOrdinals Can be in arbitrary sort order (often in rank order)
 * @param maxCharsInBudget
 * @returns
 */
export function getCountOfMessagesInCharBudget(
    messages: IMessageCollection,
    messageOrdinals: Iterable<MessageOrdinal>,
    maxCharsInBudget: number,
): number {
    let i = 0;
    let totalCharCount = 0;
    for (const messageOrdinal of messageOrdinals) {
        const message = messages.get(messageOrdinal);
        const messageCharCount = getMessageCharCount(message);
        if (messageCharCount + totalCharCount > maxCharsInBudget) {
            break;
        }
        totalCharCount += messageCharCount;
        ++i;
    }
    return i;
}

/**
 * Turn message ordinals into text ranges.. building longest contiguous ranges
 * @param messageOrdinals
 * @returns
 */
export function textRangesFromMessageOrdinals(
    messageOrdinals: MessageOrdinal[],
): TextRange[] {
    if (messageOrdinals.length === 0) {
        return [];
    }
    // Sort ordinals in ascending order
    messageOrdinals.sort((x, y) => x - y);
    let ranges: TextRange[] = [];
    let startOrdinal: MessageOrdinal | undefined = messageOrdinals[0];
    let endOrdinal = startOrdinal;
    for (let i = 1; i < messageOrdinals.length; ++i) {
        const messageOrdinal = messageOrdinals[i];
        if (messageOrdinal - endOrdinal > 1) {
            // Non-contiguous range
            ranges.push(textRangeFromMessageRange(startOrdinal, endOrdinal));
            startOrdinal = messageOrdinal;
        }
        endOrdinal = messageOrdinal;
    }
    ranges.push(textRangeFromMessageRange(startOrdinal, endOrdinal));
    return ranges;
}

export function getMaxMessageOrdinal(
    messages: IMessageCollection,
    messageOrdinalStartAt: MessageOrdinal,
    messageCount?: number,
): number {
    let maxOrdinal = messageCount
        ? messageOrdinalStartAt + messageCount
        : messages.length;
    maxOrdinal = Math.min(messages.length, maxOrdinal);
    return maxOrdinal;
}

export function* getMessageChunkBatch(
    messages: IMessageCollection,
    messageOrdinalStartAt: MessageOrdinal,
    batchSize: number,
    count?: number,
): IterableIterator<TextLocation[]> {
    let batch: TextLocation[] = [];
    let maxOrdinal = getMaxMessageOrdinal(
        messages,
        messageOrdinalStartAt,
        count,
    );
    maxOrdinal = Math.min(messages.length, maxOrdinal);
    for (
        let messageOrdinal = messageOrdinalStartAt;
        messageOrdinal < maxOrdinal;
        ++messageOrdinal
    ) {
        const message = messages.get(messageOrdinal);
        for (
            let chunkOrdinal = 0;
            chunkOrdinal < message.textChunks.length;
            ++chunkOrdinal
        ) {
            batch.push({
                messageOrdinal,
                chunkOrdinal,
            });
            if (batch.length === batchSize) {
                yield batch;
                batch = [];
            }
        }
    }
    if (batch.length > 0) {
        yield batch;
    }
}

export function* getMessagesFromOrdinals(
    messages: IMessage[],
    ordinals: Iterable<MessageOrdinal>,
) {
    for (const ordinal of ordinals) {
        yield messages[ordinal];
    }
}

export function* getMessagesFromScoredOrdinals(
    messages: IMessageCollection,
    ordinals: Iterable<ScoredMessageOrdinal>,
) {
    for (const scoredOrdinal of ordinals) {
        yield messages.get(scoredOrdinal.messageOrdinal);
    }
}

export function* getMessageOrdinalsFromScored(
    messages: IMessageCollection,
    ordinals: Iterable<ScoredMessageOrdinal>,
): IterableIterator<MessageOrdinal> {
    for (const scoredOrdinal of ordinals) {
        yield scoredOrdinal.messageOrdinal;
    }
}

export function getEnclosingTextRange(
    messageOrdinals: Iterable<MessageOrdinal>,
): TextRange | undefined {
    let start: MessageOrdinal | undefined;
    let end = start;
    for (const ordinal of messageOrdinals) {
        if (start === undefined || ordinal < start) {
            start = ordinal;
        }
        if (end === undefined || end < ordinal) {
            end = ordinal;
        }
    }
    if (start === undefined || end === undefined) {
        return undefined;
    }
    return textRangeFromMessageRange(start, end);
}

export function getEnclosingDateRangeForMessages(
    messages: IMessageCollection,
    messageOrdinals: Iterable<MessageOrdinal>,
): DateRange | undefined {
    const textRange = getEnclosingTextRange(messageOrdinals);
    if (!textRange) {
        return undefined;
    }
    return getEnclosingDateRangeForTextRange(messages, textRange);
}

export function getEnclosingDateRangeForTextRange(
    messages: IMessageCollection,
    range: TextRange,
): DateRange | undefined {
    const startTimestamp = messages.get(range.start.messageOrdinal).timestamp;
    if (!startTimestamp) {
        return undefined;
    }
    const endTimestamp = range.end
        ? messages.get(range.end.messageOrdinal).timestamp
        : undefined;
    return {
        start: new Date(startTimestamp),
        end: endTimestamp ? new Date(endTimestamp) : undefined,
    };
}

export function getEnclosingMetadataForMessages(
    messages: IMessageCollection,
    messageOrdinals: Iterable<MessageOrdinal>,
): IMessageMetadata {
    let source: Set<string> | undefined;
    let dest: Set<string> | undefined;

    for (const ordinal of messageOrdinals) {
        const metadata = messages.get(ordinal).metadata;
        if (!metadata) {
            continue;
        }
        if (metadata.source) {
            source = collect(source, metadata.source);
        }
        if (metadata.dest) {
            dest = collect(dest, metadata.dest);
        }
    }

    return {
        source: source && source.size > 0 ? [...source.values()] : undefined,
        dest: dest && dest.size > 0 ? [...dest.values()] : undefined,
    };

    function collect(
        set: Set<string> | undefined,
        values: string[] | string | undefined,
    ): Set<string> | undefined {
        if (values === undefined) {
            return set;
        }
        set ??= new Set<string>();
        if (Array.isArray(values)) {
            addToSet(set, values);
        } else {
            set.add(values);
        }
        return set;
    }
}

export function getMessageBatches(
    conversation: IConversation,
    startAtOrdinal: number,
    batchSize: number,
): IterableIterator<Batch<IMessage>> {
    return getBatchesFromCollection<IMessage>(
        conversation.messages,
        startAtOrdinal,
        batchSize,
    );
}
