import type {
    SvgNode,
    SvgPlugin,
    SvgPluginOptions,
} from "../../types/common.js";

const CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

function toShortId(n: number): string {
    if (n < CHARS.length) return CHARS[n]!;
    return (
        toShortId(Math.floor(n / CHARS.length) - 1) + CHARS[n % CHARS.length]!
    );
}

export function createMangleIds(): SvgPlugin {
    const idMap = new Map<string, string>();
    let counter = 0;

    function mangle(originalId: string): string {
        const existing = idMap.get(originalId);
        if (existing !== undefined) return existing;
        const newId = toShortId(counter++);
        idMap.set(originalId, newId);
        return newId;
    }

    function rewriteRef(ref: string): string {
        const originalId = ref.slice(1);
        return `#${mangle(originalId)}`;
    }

    return {
        name: "mangleIds",
        apply(node: SvgNode, _options: SvgPluginOptions): SvgNode | null {
            if (node.type !== "element") return node;
            const attrs = node.attributes;
            if (!attrs) return node;

            let changed = false;
            const next: Record<string, string> = { ...attrs };

            if (next["id"]) {
                next["id"] = mangle(next["id"]);
                changed = true;
            }
            if (next["href"]?.startsWith("#")) {
                next["href"] = rewriteRef(next["href"]);
                changed = true;
            }
            if (next["xlink:href"]?.startsWith("#")) {
                next["xlink:href"] = rewriteRef(next["xlink:href"]!);
                changed = true;
            }

            return changed ? { ...node, attributes: next } : node;
        },
    };
}

export const mangleIds: SvgPlugin = createMangleIds();