/*
 * macros.ts — macro parsing and Tag generation for ribbit.
 *
 * Macros use @name(...) syntax. Ribbit automatically wraps macro output
 * in an element with data- attributes that preserve the original source.
 * Round-tripping is handled generically — consumers only write toHTML.
 *
 * Syntax:
 *   @user                              — bare, no args
 *   @user()                            — empty parens, same as bare
 *   @npc(Goblin King)                  — self-closing with keywords
 *   @toc(depth="3")                    — self-closing with params
 *   @style(box center                  — block: newline after args = content
 *   **Bold** content here.
 *   )
 *   @style(box verbatim                — verbatim block
 *   Literal <b>content</b>.
 *   )
 */

import type { Tag, SourceToken, Converter, MatchContext } from './types';
import { escapeHtml } from './tags';

export interface MacroDef {
    name: string;
    /**
     * Render the macro's inner HTML. Ribbit wraps the result in an
     * element with data- attributes for round-tripping.
     *
     *   { name: 'user', toHTML: () => '<a href="/User/gsb">gsb</a>' }
     *   { name: 'style', toHTML: ({ keywords, content }) =>
     *       `<div class="${keywords.join(' ')}">${content}</div>` }
     */
    toHTML: (context: {
        keywords: string[];
        params: Record<string, string>;
        content?: string;
        convert: Converter;
    }) => string;
}

interface ParsedMacro {
    name: string;
    keywords: string[];
    params: Record<string, string>;
    verbatim: boolean;
    content?: string;
    consumed: number;
}

const PARAM_PATTERN = /(\w+)="([^"]*)"/g;

function parseArgs(argsStr: string | undefined): {
    keywords: string[];
    params: Record<string, string>;
    verbatim: boolean;
} {
    if (!argsStr || !argsStr.trim()) {
        return { keywords: [], params: {}, verbatim: false };
    }
    const params: Record<string, string> = {};
    const withoutParams = argsStr.replace(new RegExp(PARAM_PATTERN.source, 'g'), (_, key, val) => {
        params[key] = val;
        return '';
    });
    const allKeywords = withoutParams.trim().split(/\s+/).filter(Boolean);
    const verbatim = allKeywords.includes('verbatim');
    const keywords = allKeywords.filter(k => k !== 'verbatim');
    return { keywords, params, verbatim };
}

function macroError(name: string): string {
    return `<span class="ribbit-error">Unknown macro: @${escapeHtml(name)}</span>`;
}

/**
 * Wrap a macro's rendered HTML with data- attributes for round-tripping.
 * Block macros (with content) use <div>, inline macros use <span>.
 */
function wrapMacro(
    name: string,
    keywords: string[],
    params: Record<string, string>,
    verbatim: boolean,
    hasContent: boolean,
    innerHtml: string,
): string {
    const tag = hasContent ? 'div' : 'span';
    let attrs = ` data-macro="${escapeHtml(name)}"`;
    if (keywords.length) {
        attrs += ` data-keywords="${escapeHtml(keywords.join(' '))}"`;
    }
    for (const [key, val] of Object.entries(params)) {
        attrs += ` data-param-${escapeHtml(key)}="${escapeHtml(val)}"`;
    }
    if (verbatim) {
        attrs += ` data-verbatim="true"`;
    }
    return `<${tag}${attrs}>${innerHtml}</${tag}>`;
}

/**
 * Reconstruct macro source from a DOM element's data- attributes.
 * This is the generic toMarkdown for all macros.
 */
function macroToMarkdown(element: HTMLElement, convert: Converter): string {
    const name = element.dataset.macro || '';
    const keywords = element.dataset.keywords || '';
    const verbatim = element.dataset.verbatim === 'true';

    const paramParts: string[] = [];
    for (const [key, val] of Object.entries(element.dataset)) {
        if (key.startsWith('param') && key.length > 5) {
            const paramName = key.slice(5).toLowerCase();
            paramParts.push(`${paramName}="${val}"`);
        }
    }

    const allKeywords = verbatim
        ? [keywords, 'verbatim'].filter(Boolean).join(' ')
        : keywords;
    const args = [allKeywords, paramParts.join(' ')].filter(Boolean).join(' ');

    const isBlock = element.tagName === 'DIV';
    if (isBlock) {
        const content = convert.children(element);
        return `\n\n@${name}(${args}\n${content}\n)\n\n`;
    }
    return args ? `@${name}(${args})` : `@${name}`;
}

/**
 * Try to parse a block macro starting at the given line index.
 */
function parseBlockMacro(lines: string[], index: number): ParsedMacro | null {
    const line = lines[index];
    const m = line.match(/^@(\w+)\(([^)]*)\s*$/);
    if (!m) {
        return null;
    }
    const name = m[1];
    const { keywords, params, verbatim } = parseArgs(m[2]);
    const contentLines: string[] = [];
    let i = index + 1;
    let depth = 1;
    while (i < lines.length && depth > 0) {
        if (/^\)\s*$/.test(lines[i])) {
            depth--;
            if (depth === 0) {
                break;
            }
        }
        if (/^@\w+\([^)]*\s*$/.test(lines[i])) {
            depth++;
        }
        contentLines.push(lines[i]);
        i++;
    }
    if (depth !== 0) {
        return null;
    }
    return {
        name,
        keywords,
        params,
        verbatim,
        content: contentLines.join('\n'),
        consumed: i + 1 - index,
    };
}

const INLINE_MACRO_GLOBAL = /(?:^|(?<=[\s*_(>|]))@(\w+)(?:\(([^)]*)\))?/g;

/**
 * Build Tags from an array of macro definitions.
 */
export function buildMacroTags(
    macros: MacroDef[],
): { blockTag: Tag; selectorTag: Tag; macroMap: Map<string, MacroDef> } {
    const macroMap = new Map<string, MacroDef>();
    for (const macro of macros) {
        macroMap.set(macro.name, macro);
    }

    const blockTag: Tag = {
        /*
         * @name(args
         * content
         * )
         */
        name: 'macro',
        match: (context) => {
            const parsed = parseBlockMacro(context.lines, context.index);
            if (!parsed) {
                return null;
            }
            return {
                content: parsed.content || '',
                raw: JSON.stringify(parsed),
                consumed: parsed.consumed,
            };
        },
        toHTML: (token, convert) => {
            const parsed: ParsedMacro = JSON.parse(token.raw);
            const macro = macroMap.get(parsed.name);
            if (!macro) {
                return macroError(parsed.name);
            }
            let content = parsed.content;
            if (content !== undefined) {
                if (parsed.verbatim) {
                    content = escapeHtml(content.trim()).replace(/\n/g, '<br>\n');
                } else {
                    content = convert.block(content);
                }
            }
            const innerHtml = macro.toHTML({
                keywords: parsed.keywords,
                params: parsed.params,
                content,
                convert,
            });
            return wrapMacro(
                parsed.name, parsed.keywords, parsed.params,
                parsed.verbatim, true, innerHtml,
            );
        },
        selector: '[data-macro]',
        toMarkdown: () => '',
    };

    /**
     * Generic selector tag that matches any element with data-macro
     * and reconstructs the macro source from data- attributes.
     */
    const selectorTag: Tag = {
        name: 'macro:generic',
        match: () => null,
        toHTML: () => '',
        selector: '[data-macro]',
        toMarkdown: macroToMarkdown,
    };

    return { blockTag, selectorTag, macroMap };
}

/**
 * Process inline macros in a text string, replacing them with rendered HTML.
 */
export function processInlineMacros(
    text: string,
    macroMap: Map<string, MacroDef>,
    convert: Converter,
    placeholders: string[],
): string {
    return text.replace(INLINE_MACRO_GLOBAL, (match, nameStr: string, argsStr: string | undefined) => {
        const macro = macroMap.get(nameStr);
        if (!macro) {
            placeholders.push(macroError(nameStr));
            return '\x00P' + (placeholders.length - 1) + '\x00';
        }
        const { keywords, params } = parseArgs(argsStr);
        const innerHtml = macro.toHTML({
            keywords,
            params,
            convert,
        });
        const wrapped = wrapMacro(nameStr, keywords, params, false, false, innerHtml);
        placeholders.push(wrapped);
        return '\x00P' + (placeholders.length - 1) + '\x00';
    });
}