/*
Copyright 2019 The Matrix.org Foundation C.I.C.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import Range from "./range";
import { Part, Type } from "./parts";

/**
 * Some common queries and transformations on the editor model
 */

export function replaceRangeAndExpandSelection(range: Range, newParts: Part[]): void {
    const { model } = range;
    model.transform(() => {
        const oldLen = range.length;
        const addedLen = range.replace(newParts);
        const firstOffset = range.start.asOffset(model);
        const lastOffset = firstOffset.add(oldLen + addedLen);
        return model.startRange(firstOffset.asPosition(model), lastOffset.asPosition(model));
    });
}

export function replaceRangeAndMoveCaret(range: Range, newParts: Part[]): void {
    const { model } = range;
    model.transform(() => {
        const oldLen = range.length;
        const addedLen = range.replace(newParts);
        const firstOffset = range.start.asOffset(model);
        const lastOffset = firstOffset.add(oldLen + addedLen);
        return lastOffset.asPosition(model);
    });
}

export function rangeStartsAtBeginningOfLine(range: Range): boolean {
    const { model } = range;
    const startsWithPartial = range.start.offset !== 0;
    const isFirstPart = range.start.index === 0;
    const previousIsNewline = !isFirstPart && model.parts[range.start.index - 1].type === Type.Newline;
    return !startsWithPartial && (isFirstPart || previousIsNewline);
}

export function rangeEndsAtEndOfLine(range: Range): boolean {
    const { model } = range;
    const lastPart = model.parts[range.end.index];
    const endsWithPartial = range.end.offset !== lastPart.text.length;
    const isLastPart = range.end.index === model.parts.length - 1;
    const nextIsNewline = !isLastPart && model.parts[range.end.index + 1].type === Type.Newline;
    return !endsWithPartial && (isLastPart || nextIsNewline);
}

export function formatRangeAsQuote(range: Range): void {
    const { model, parts } = range;
    const { partCreator } = model;
    for (let i = 0; i < parts.length; ++i) {
        const part = parts[i];
        if (part.type === Type.Newline) {
            parts.splice(i + 1, 0, partCreator.plain("> "));
        }
    }
    parts.unshift(partCreator.plain("> "));
    if (!rangeStartsAtBeginningOfLine(range)) {
        parts.unshift(partCreator.newline());
    }
    if (!rangeEndsAtEndOfLine(range)) {
        parts.push(partCreator.newline());
    }

    parts.push(partCreator.newline());
    replaceRangeAndExpandSelection(range, parts);
}

export function formatRangeAsCode(range: Range): void {
    const { model, parts } = range;
    const { partCreator } = model;
    const needsBlock = parts.some(p => p.type === Type.Newline);
    if (needsBlock) {
        parts.unshift(partCreator.plain("```"), partCreator.newline());
        if (!rangeStartsAtBeginningOfLine(range)) {
            parts.unshift(partCreator.newline());
        }
        parts.push(
            partCreator.newline(),
            partCreator.plain("```"));
        if (!rangeEndsAtEndOfLine(range)) {
            parts.push(partCreator.newline());
        }
    } else {
        parts.unshift(partCreator.plain("`"));
        parts.push(partCreator.plain("`"));
    }
    replaceRangeAndExpandSelection(range, parts);
}

// parts helper methods
const isBlank = part => !part.text || !/\S/.test(part.text);
const isNL = part => part.type === Type.Newline;

export function toggleInlineFormat(range: Range, prefix: string, suffix = prefix): void {
    const { model, parts } = range;
    const { partCreator } = model;

    // compute paragraph [start, end] indexes
    const paragraphIndexes = [];
    let startIndex = 0;
    // start at i=2 because we look at i and up to two parts behind to detect paragraph breaks at their end
    for (let i = 2; i < parts.length; i++) {
        // paragraph breaks can be denoted in a multitude of ways,
        // - 2 newline parts in sequence
        // - newline part, plain(<empty or just spaces>), newline part

        // bump startIndex onto the first non-blank after the paragraph ending
        if (isBlank(parts[i - 2]) && isNL(parts[i - 1]) && !isNL(parts[i]) && !isBlank(parts[i])) {
            startIndex = i;
        }

        // if at a paragraph break, store the indexes of the paragraph
        if (isNL(parts[i - 1]) && isNL(parts[i])) {
            paragraphIndexes.push([startIndex, i - 1]);
            startIndex = i + 1;
        } else if (isNL(parts[i - 2]) && isBlank(parts[i - 1]) && isNL(parts[i])) {
            paragraphIndexes.push([startIndex, i - 2]);
            startIndex = i + 1;
        }
    }

    const lastNonEmptyPart = parts.map(isBlank).lastIndexOf(false);
    // If we have not yet included the final paragraph then add it now
    if (startIndex <= lastNonEmptyPart) {
        paragraphIndexes.push([startIndex, lastNonEmptyPart + 1]);
    }

    // keep track of how many things we have inserted as an offset:=0
    let offset = 0;
    paragraphIndexes.forEach(([startIdx, endIdx]) => {
        // for each paragraph apply the same rule
        const base = startIdx + offset;
        const index = endIdx + offset;

        const isFormatted = (index - base > 0) &&
            parts[base].text.startsWith(prefix) &&
            parts[index - 1].text.endsWith(suffix);

        if (isFormatted) {
            // remove prefix and suffix
            const partWithoutPrefix = parts[base].serialize();
            partWithoutPrefix.text = partWithoutPrefix.text.substr(prefix.length);
            parts[base] = partCreator.deserializePart(partWithoutPrefix);

            const partWithoutSuffix = parts[index - 1].serialize();
            const suffixPartText = partWithoutSuffix.text;
            partWithoutSuffix.text = suffixPartText.substring(0, suffixPartText.length - suffix.length);
            parts[index - 1] = partCreator.deserializePart(partWithoutSuffix);
        } else {
            parts.splice(index, 0, partCreator.plain(suffix)); // splice in the later one first to not change offset
            parts.splice(base, 0, partCreator.plain(prefix));
            offset += 2; // offset index to account for the two items we just spliced in
        }
    });

    replaceRangeAndExpandSelection(range, parts);
}
