src/frontend/app/maps/styleloader.ts


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import type { StyleSpecification } from "react-map-gl/maplibre";

export async function loadStyle(styleName: string, colorScheme: string): Promise<StyleSpecification> {
    const stylePath = `/maps/styles/${styleName}-${colorScheme}.json`;
    const resp = await fetch(stylePath);

    if (!resp.ok) {
        throw new Error(`Failed to load style: ${stylePath}`);
    }

    const style = await resp.json();

    const baseUrl = window.location.origin;
    const spritePath = style.sprite;

    // Handle both string and array cases for spritePath
    if (Array.isArray(spritePath)) {
        // For array format, update each sprite object's URL to be absolute
        style.sprite = spritePath.map(spriteObj => {
            const isAbsoluteUrl = spriteObj.url.startsWith("http://") || spriteObj.url.startsWith("https://");
            if (isAbsoluteUrl) {
                return spriteObj;
            }

            return {
                ...spriteObj,
                url: `${baseUrl}${spriteObj.url}`
            };
        });
    } else if (typeof spritePath === "string") {
        if (!spritePath.startsWith("http://") && !spritePath.startsWith("https://")) {
            style.sprite = `${baseUrl}${spritePath}`;
        }
    }

    // Detect on each source if it the 'tiles' URLs are relative and convert them to absolute URLs
    for (const sourceKey in style.sources) {
        const source = style.sources[sourceKey];
        for (const tileKey in source.tiles) {
            const tileUrl = source.tiles[tileKey];
            const isAbsoluteUrl = tileUrl.startsWith("http://") || tileUrl.startsWith("https://");
            if (!isAbsoluteUrl) {
                source.tiles[tileKey] = `${baseUrl}${tileUrl}`;
            }
        }
    }

    return style as StyleSpecification;
}