import React from 'react';
import {
    Editor,
    Modifier,
    ContentState,
    ContentBlock,
    convertFromHTML,
    DefaultDraftBlockRenderMap,
    DefaultDraftInlineStyle,
    CompositeDecorator,
    SelectionState,
} from 'draft-js';
import * as sdk from  './index';
import * as emojione from 'emojione';

const BLOCK_RENDER_MAP = DefaultDraftBlockRenderMap.set('unstyled', {
    element: 'span'
    /*
     draft uses <div> by default which we don't really like, so we're using <span>
     this is probably not a good idea since <span> is not a block level element but
     we're trying to fix things in contentStateToHTML below
     */
});

const STYLES = {
    BOLD: 'strong',
    CODE: 'code',
    ITALIC: 'em',
    STRIKETHROUGH: 's',
    UNDERLINE: 'u',
};

const MARKDOWN_REGEX = {
    LINK: /(?:\[([^\]]+)\]\(([^\)]+)\))|\<(\w+:\/\/[^\>]+)\>/g,
    ITALIC: /([\*_])([\w\s]+?)\1/g,
    BOLD: /([\*_])\1([\w\s]+?)\1\1/g,
};

const USERNAME_REGEX = /@\S+:\S+/g;
const ROOM_REGEX = /#\S+:\S+/g;
const EMOJI_REGEX = new RegExp(emojione.unicodeRegexp, 'g');

export function contentStateToHTML(contentState: ContentState): string {
    return contentState.getBlockMap().map((block) => {
        let elem = BLOCK_RENDER_MAP.get(block.getType()).element;
        let content = [];
        block.findStyleRanges(
            () => true, // always return true => don't filter any ranges out
            (start, end) => {
                // map style names to elements
                let tags = block.getInlineStyleAt(start).map(style => STYLES[style]).filter(style => !!style);
                // combine them to get well-nested HTML
                let open = tags.map(tag => `<${tag}>`).join('');
                let close = tags.map(tag => `</${tag}>`).reverse().join('');
                // and get the HTML representation of this styled range (this .substring() should never fail)
                let text = block.getText().substring(start, end);
                // http://shebang.brandonmintern.com/foolproof-html-escaping-in-javascript/
                let div = document.createElement('div');
                div.appendChild(document.createTextNode(text));
                let safeText = div.innerHTML;
                content.push(`${open}${safeText}${close}`);
            }
        );

        let result = `<${elem}>${content.join('')}</${elem}>`;

        // dirty hack because we don't want block level tags by default, but breaks
        if(elem === 'span')
            result += '<br />';
        return result;
    }).join('');
}

export function HTMLtoContentState(html: string): ContentState {
    return ContentState.createFromBlockArray(convertFromHTML(html));
}

/**
 * Returns a composite decorator which has access to provided scope.
 */
export function getScopedRTDecorators(scope: any): CompositeDecorator {
    let MemberAvatar = sdk.getComponent('avatars.MemberAvatar');

    let usernameDecorator = {
        strategy: (contentBlock, callback) => {
            findWithRegex(USERNAME_REGEX, contentBlock, callback);
        },
        component: (props) => {
            let member = scope.room.getMember(props.children[0].props.text);
            // unused until we make these decorators immutable (autocomplete needed)
            let name = member ? member.name : null;
            let avatar = member ? <MemberAvatar member={member} width={16} height={16}/> : null;
            return <span className="mx_UserPill">{avatar} {props.children}</span>;
        }
    };
    
    let roomDecorator = {
        strategy: (contentBlock, callback) => {
            findWithRegex(ROOM_REGEX, contentBlock, callback);
        },
        component: (props) => {
            return <span className="mx_RoomPill">{props.children}</span>;
        }
    };

    // Unused for now, due to https://github.com/facebook/draft-js/issues/414
    let emojiDecorator = {
        strategy: (contentBlock, callback) => {
            findWithRegex(EMOJI_REGEX, contentBlock, callback);
        },
        component: (props) => {
            return <span dangerouslySetInnerHTML={{__html: ' ' + emojione.unicodeToImage(props.children[0].props.text)}}/>
        }
    };

    return [usernameDecorator, roomDecorator];
}

export function getScopedMDDecorators(scope: any): CompositeDecorator {
    let markdownDecorators = ['BOLD', 'ITALIC'].map(
        (style) => ({
            strategy: (contentBlock, callback) => {
                return findWithRegex(MARKDOWN_REGEX[style], contentBlock, callback);
            },
            component: (props) => (
                <span className={"mx_MarkdownElement mx_Markdown_" + style}>
                    {props.children}
                </span>
            )
        }));

    markdownDecorators.push({
        strategy: (contentBlock, callback) => {
            return findWithRegex(MARKDOWN_REGEX.LINK, contentBlock, callback);
        },
        component: (props) => (
            <a href="#" className="mx_MarkdownElement mx_Markdown_LINK">
                {props.children}
            </a>
        )
    });

    return markdownDecorators;
}

/**
 * Utility function that looks for regex matches within a ContentBlock and invokes {callback} with (start, end)
 * From https://facebook.github.io/draft-js/docs/advanced-topics-decorators.html
 */
function findWithRegex(regex, contentBlock: ContentBlock, callback: (start: number, end: number) => any) {
    const text = contentBlock.getText();
    let matchArr, start;
    while ((matchArr = regex.exec(text)) !== null) {
        start = matchArr.index;
        callback(start, start + matchArr[0].length);
    }
}

/**
 * Passes rangeToReplace to modifyFn and replaces it in contentState with the result.
 */
export function modifyText(contentState: ContentState, rangeToReplace: SelectionState,
                           modifyFn: (text: string) => string, inlineStyle, entityKey): ContentState {
    let getText = (key) => contentState.getBlockForKey(key).getText(),
        startKey = rangeToReplace.getStartKey(),
        startOffset = rangeToReplace.getStartOffset(),
        endKey = rangeToReplace.getEndKey(),
        endOffset = rangeToReplace.getEndOffset(),
        text = "";


    for (let currentKey = startKey;
            currentKey && currentKey !== endKey;
            currentKey = contentState.getKeyAfter(currentKey)) {
        let blockText = getText(currentKey);
        text += blockText.substring(startOffset, blockText.length);

        // from now on, we'll take whole blocks
        startOffset = 0;
    }

    // add remaining part of last block
    text += getText(endKey).substring(startOffset, endOffset);

    return Modifier.replaceText(contentState, rangeToReplace, modifyFn(text), inlineStyle, entityKey);
}

/**
 * Computes the plaintext offsets of the given SelectionState.
 * Note that this inherently means we make assumptions about what that means (no separator between ContentBlocks, etc)
 * Used by autocomplete to show completions when the current selection lies within, or at the edges of a command.
 */
export function selectionStateToTextOffsets(selectionState: SelectionState,
                                            contentBlocks: Array<ContentBlock>): {start: number, end: number} {
    let offset = 0, start = 0, end = 0;
    for(let block of contentBlocks) {
        if (selectionState.getStartKey() === block.getKey()) {
            start = offset + selectionState.getStartOffset();
        }
        if (selectionState.getEndKey() === block.getKey()) {
            end = offset + selectionState.getEndOffset();
            break;
        }
        offset += block.getLength();
    }

    return {
        start,
        end,
    };
}

export function textOffsetsToSelectionState({start, end}: {start: number, end: number},
                                            contentBlocks: Array<ContentBlock>): SelectionState {
    let selectionState = SelectionState.createEmpty();

    for (let block of contentBlocks) {
        let blockLength = block.getLength();

        if (start !== -1 && start < blockLength) {
            selectionState = selectionState.merge({
                anchorKey: block.getKey(),
                anchorOffset: start,
            });
            start = -1;
        } else {
            start -= blockLength;
        }

        if (end !== -1 && end <= blockLength) {
            selectionState = selectionState.merge({
                focusKey: block.getKey(),
                focusOffset: end,
            });
            end = -1;
        } else {
            end -= blockLength;
        }
    }

    return selectionState;
}