/*
   ELYSIA MARKDOWN STUDIO v1.0 - Preview Module
   Real-time Markdown preview with extensions
*/

import Utils from "./utils.js";

const Preview = {
    container: null,
    renderer: null,

    init() {
        this.container = document.getElementById("markdown-preview");
        this.setupMarked();
        this.setupMermaid();
    },

    setupMarked() {
        // Configure marked.js v15+ (async API)
        marked.setOptions({
            breaks: true,
            gfm: true, // GitHub Flavored Markdown
            headerIds: true
        });

        // Custom renderer for task lists (Marked.js v15+ token-based API)
        const renderer = {
            listitem(token) {
                // In v15+, token has 'task' and 'checked' properties
                if (token.task) {
                    return `<li class="task-list-item">
                        <input type="checkbox" ${token.checked ? "checked" : ""} disabled> ${token.text}
                    </li>\n`;
                }

                // Regular list item
                return `<li>${token.text}</li>\n`;
            },

            code(token) {
                const lang = token.lang || "";
                const code = token.text;

                // Highlight with Prism if available
                if (lang && window.Prism && Prism.languages[lang]) {
                    const highlighted = Prism.highlight(code, Prism.languages[lang], lang);
                    return `<pre><code class="language-${lang}">${highlighted}</code></pre>\n`;
                }

                return `<pre><code>${code}</code></pre>\n`;
            }
        };

        marked.use({ renderer });
    },

    setupMermaid() {
        if (window.mermaid) {
            mermaid.initialize({
                startOnLoad: false,
                theme: "dark",
                securityLevel: "loose"
            });
        }
    },

    update() {
        const content = window.app?.editor.getContent() || "";
        this.render(content);
    },

    async render(markdown) {
        if (!markdown) {
            this.container.innerHTML = '<p style="color: var(--text-tertiary); text-align: center; padding: 2rem;">Start writing to see preview...</p>';
            return;
        }

        try {
            // Convert markdown to HTML (v15+ can be async)
            let html = await marked.parse(markdown);

            // Ensure html is a string, not an object
            if (typeof html !== "string") {
                console.error("Marked.parse returned non-string:", typeof html, html);
                html = String(html);
            }

            // Process KaTeX math
            html = this.processKaTeX(html);

            // Update container
            this.container.innerHTML = html;

            // Render mermaid diagrams
            this.renderMermaid();

            // Highlight code blocks
            this.highlightCode();
        } catch (err) {
            console.error("Preview render failed:", err);
            this.container.innerHTML = `<p style="color: var(--error);">Preview error: ${err.message}</p>`;
        }
    },

    processKaTeX(html) {
        if (!window.katex) return html;

        // Inline math: $...$
        html = html.replace(/\$([^\$]+)\$/g, (match, math) => {
            try {
                return katex.renderToString(math, { throwOnError: false });
            } catch {
                return match;
            }
        });

        // Block math: $$...$$
        html = html.replace(/\$\$([^\$]+)\$\$/g, (match, math) => {
            try {
                return katex.renderToString(math, {
                    throwOnError: false,
                    displayMode: true
                });
            } catch {
                return match;
            }
        });

        return html;
    },

    renderMermaid() {
        if (!window.mermaid) return;

        const mermaidBlocks = this.container.querySelectorAll("code.language-mermaid");
        mermaidBlocks.forEach((block, index) => {
            const code = block.textContent;
            const id = `mermaid-${Date.now()}-${index}`;

            const div = document.createElement("div");
            div.id = id;
            div.className = "mermaid";
            div.textContent = code;

            block.parentElement.replaceWith(div);

            try {
                mermaid.init(undefined, `#${id}`);
            } catch (err) {
                console.warn("Mermaid render failed:", err);
            }
        });
    },

    highlightCode() {
        if (!window.Prism) return;

        this.container.querySelectorAll("pre code").forEach(block => {
            if (!block.classList.contains("language-mermaid")) {
                Prism.highlightElement(block);
            }
        });
    },

    // Get current HTML (for export)
    getHTML() {
        if (!this.container) {
            console.warn("Preview container not initialized");
            return "";
        }
        return this.container.innerHTML;
    },

    // Apply theme
    setTheme(theme) {
        if (!this.container) {
            console.warn("Preview container not initialized yet");
            return;
        }

        if (theme === "github") {
            this.container.classList.add("theme-github");
            this.container.classList.remove("theme-elysia");
        } else {
            this.container.classList.add("theme-elysia");
            this.container.classList.remove("theme-github");
        }
    }
};

export default Preview;