src/shared/layout-schema.js

// ══════════════════════════════════════════════════════════════════════════════
// Chahua Markdown Presenter - Layout Schema & Tree Builder
// Converts parsed markdown slides into structured presentation layout blocks
// ══════════════════════════════════════════════════════════════════════════════
// Company: Chahua Development Co., Ltd.
// Version: 1.0.0
// License: MIT
// ══════════════════════════════════════════════════════════════════════════════

const LayoutNodeKind = {
    SLIDE: 'slide',
    SECTION: 'section',
    HEADING: 'heading',
    TEXT: 'text',
    LIST: 'list',
    CODE: 'code',
    TABLE: 'table',
    CALLOUT: 'callout',
    IMAGE: 'image',
    DIVIDER: 'divider',
    HTML: 'html',
    LINK: 'link'
};

const ListKind = {
    UNORDERED: 'unordered',
    ORDERED: 'ordered',
    TASK: 'task'
};

let layoutIdCounter = 0;
function nextLayoutId(prefix) {
    layoutIdCounter += 1;
    return `${prefix}-${layoutIdCounter}`;
}

const HEADING_LINE_WEIGHTS = {
    1: 3.2,
    2: 2.6,
    3: 2,
    4: 1.6,
    5: 1.4,
    6: 1.2
};

function estimateTextLines(text) {
    if (!text) return 1;
    const words = text.trim().split(/\s+/).length;
    return Math.max(1, Math.ceil(words / 12));
}

function estimateListLines(items) {
    if (!items || items.length === 0) return 0;
    return items.reduce((sum, item) => sum + Math.max(1.1, estimateTextLines(item.text) * 0.85), 0);
}

function estimateBlockLines(block) {
    switch (block.kind) {
        case LayoutNodeKind.HEADING:
            return HEADING_LINE_WEIGHTS[block.level] || 2.4;
        case LayoutNodeKind.TEXT:
            return estimateTextLines(block.text);
        case LayoutNodeKind.LIST:
            return estimateListLines(block.items) + 0.5;
        case LayoutNodeKind.CODE: {
            const lines = block.content.split('\n').length;
            return Math.min(12, lines + 1.5);
        }
        case LayoutNodeKind.TABLE: {
            const rows = block.rows ? block.rows.length : 0;
            return 2.5 + rows * 0.8;
        }
        case LayoutNodeKind.CALLOUT:
            return Math.max(2, estimateTextLines(block.text) * 1.2);
        case LayoutNodeKind.IMAGE:
            return 4.5;
        case LayoutNodeKind.DIVIDER:
            return 0.5;
        case LayoutNodeKind.HTML:
            return 3;
        case LayoutNodeKind.LINK:
            return Math.max(1, estimateTextLines(block.text));
        default:
            return 1;
    }
}

function createHeadingBlock(level, text, html = null) {
    const normalizedLevel = Math.min(Math.max(level || 1, 1), 6);
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.HEADING,
        level: normalizedLevel,
        text: text || '',
        html: html || null
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createSectionFromHeading(headingItem, fallbackTitle, fallbackLevel = 2) {
    const level = headingItem ? parseInt(headingItem.type.replace('h', ''), 10) || fallbackLevel : fallbackLevel;
    const title = headingItem ? headingItem.content : fallbackTitle;

    const section = {
        id: nextLayoutId('section'),
        kind: LayoutNodeKind.SECTION,
        level,
        title: title || fallbackTitle || '',
        heading: headingItem || null,
        blocks: [],
        metrics: {
            estimatedLines: 0
        }
    };

    const headingText = title || fallbackTitle || '';
    if (headingText) {
        const headingBlock = createHeadingBlock(level, headingText, headingItem?.html || null);
        section.blocks.push(headingBlock);
        section.metrics.estimatedLines += headingBlock.metrics.estimatedLines;
    }

    return section;
}

function createTextBlock(text, html = null) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.TEXT,
        text,
        html: html || null
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createListBlock(listType) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.LIST,
        listType,
        items: []
    };
    block.metrics = { estimatedLines: 0 };
    return block;
}

function createCodeBlock(item) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.CODE,
        language: item.language || 'text',
        content: item.content
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createTableBlock(item) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.TABLE,
        rows: item.rows || []
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createCalloutBlock(item) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.CALLOUT,
        text: item.content,
        level: item.level || 1,
        html: item.html || null
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createImageBlock(item) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.IMAGE,
        src: item.src,
        alt: item.alt || '',
        title: item.title || ''
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createDividerBlock() {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.DIVIDER
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createHtmlBlock(item) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.HTML,
        html: item.html || item.content
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function createLinkBlock(item) {
    const block = {
        id: nextLayoutId('block'),
        kind: LayoutNodeKind.LINK,
        text: item.text || item.content || '',
        href: item.url || item.href || '',
        title: item.title || '',
        html: item.html || null
    };
    block.metrics = { estimatedLines: estimateBlockLines(block) };
    return block;
}

function appendBlockToSection(section, block) {
    section.blocks.push(block);
    section.metrics.estimatedLines += block.metrics.estimatedLines;
}

function appendListItem(block, item) {
    block.items.push({
        id: nextLayoutId('listitem'),
        text: item.content,
        marker: item.marker || null,
        number: item.number || null,
        checked: !!item.checked,
        html: item.html || null
    });
    block.metrics.estimatedLines = estimateBlockLines(block);
}

function resolveListType(itemType) {
    if (itemType === 'numbered-item') return ListKind.ORDERED;
    if (itemType === 'task-list') return ListKind.TASK;
    return ListKind.UNORDERED;
}

function addItemToSection(section, item) {
    switch (item.type) {
        case 'text': {
            const lastBlock = section.blocks[section.blocks.length - 1];
            if (lastBlock && lastBlock.kind === LayoutNodeKind.TEXT) {
                const previousLines = lastBlock.metrics.estimatedLines;
                lastBlock.text = `${lastBlock.text}\n\n${item.content}`;
                if (item.html) {
                    const joiner = lastBlock.html ? '<br><br>' : '';
                    lastBlock.html = lastBlock.html ? `${lastBlock.html}${joiner}${item.html}` : item.html;
                }
                lastBlock.metrics.estimatedLines = estimateBlockLines(lastBlock);
                section.metrics.estimatedLines += (lastBlock.metrics.estimatedLines - previousLines);
            } else {
                appendBlockToSection(section, createTextBlock(item.content, item.html || null));
            }
            break;
        }
        case 'list-item':
        case 'numbered-item':
        case 'task-list': {
            const listType = resolveListType(item.type);
            let listBlock = section.blocks[section.blocks.length - 1];
            if (!listBlock || listBlock.kind !== LayoutNodeKind.LIST || listBlock.listType !== listType) {
                listBlock = createListBlock(listType);
                appendBlockToSection(section, listBlock);
            }
            const previousLines = listBlock.metrics.estimatedLines;
            appendListItem(listBlock, item);
            section.metrics.estimatedLines += (listBlock.metrics.estimatedLines - previousLines);
            break;
        }
        case 'code':
            appendBlockToSection(section, createCodeBlock(item));
            break;
        case 'table':
            appendBlockToSection(section, createTableBlock(item));
            break;
        case 'blockquote':
            appendBlockToSection(section, createCalloutBlock(item));
            break;
        case 'image':
            appendBlockToSection(section, createImageBlock(item));
            break;
        case 'hr':
            appendBlockToSection(section, createDividerBlock());
            break;
        case 'html':
            appendBlockToSection(section, createHtmlBlock(item));
            break;
        case 'link':
            appendBlockToSection(section, createLinkBlock(item));
            break;
        default:
            appendBlockToSection(section, createTextBlock(item.content || '', item.html || null));
            break;
    }
}

export function buildLayoutTreeForSlide(slide) {
    const root = {
        id: nextLayoutId('slide'),
        kind: LayoutNodeKind.SLIDE,
        title: slide.title || '',
        subtitle: slide.subtitle || '',
        sections: [],
        metrics: {
            estimatedLines: 0
        }
    };

    let currentSection = null;

    const ensureSection = (headingItem = null) => {
        if (headingItem) {
            currentSection = createSectionFromHeading(headingItem, slide.title);
            root.sections.push(currentSection);
        } else if (!currentSection) {
            currentSection = createSectionFromHeading(null, slide.title || '');
            root.sections.push(currentSection);
        }
        return currentSection;
    };

    const contentItems = Array.isArray(slide.content) ? slide.content : [];
    for (const item of contentItems) {
        if (item.type && /^h[1-6]$/.test(item.type)) {
            ensureSection(item);
            continue;
        }

        ensureSection();
        addItemToSection(currentSection, item);
    }

    if (root.sections.length === 0) {
        currentSection = createSectionFromHeading(null, slide.title || 'Overview');
        root.sections.push(currentSection);
        if (contentItems.length === 0 && slide.subtitle) {
            appendBlockToSection(currentSection, createTextBlock(slide.subtitle));
        }
    }

    root.metrics.estimatedLines = root.sections.reduce((sum, section) => {
        return sum + (section.metrics?.estimatedLines || 0);
    }, 0);

    return root;
}

export { 
    LayoutNodeKind, 
    ListKind, 
    estimateBlockLines 
};