/**
 * 将 SVG 字符串转为小程序可用的 data URL（base64 在真机上更稳定）
 */

function utf8ToBytes(str) {
    const encoded = encodeURIComponent(str)
    const bytes = []
    for (let i = 0; i < encoded.length; i++) {
        if (encoded.charCodeAt(i) === 37) {
            bytes.push(parseInt(encoded.substring(i + 1, i + 3), 16))
            i += 2
        } else {
            bytes.push(encoded.charCodeAt(i))
        }
    }
    return new Uint8Array(bytes)
}

function bytesToBase64(bytes) {
    if (typeof uni !== 'undefined' && typeof uni.arrayBufferToBase64 === 'function') {
        return uni.arrayBufferToBase64(bytes.buffer)
    }
    if (typeof btoa !== 'undefined') {
        let binary = ''
        for (let i = 0; i < bytes.length; i++) {
            binary += String.fromCharCode(bytes[i])
        }
        return btoa(binary)
    }
    const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
    let result = ''
    for (let i = 0; i < bytes.length; i += 3) {
        const a = bytes[i]
        const b = i + 1 < bytes.length ? bytes[i + 1] : 0
        const c = i + 2 < bytes.length ? bytes[i + 2] : 0
        result += chars[a >> 2]
        result += chars[((a & 3) << 4) | (b >> 4)]
        result += i + 1 < bytes.length ? chars[((b & 15) << 2) | (c >> 6)] : '='
        result += i + 2 < bytes.length ? chars[c & 63] : '='
    }
    return result
}

export function svgToDataUrl(svg) {
    const normalized = String(svg || '').trim()
    if (!normalized) return ''
    const base64 = bytesToBase64(utf8ToBytes(normalized))
    return `data:image/svg+xml;base64,${base64}`
}