import { clamp, progress } from 'motion-utils';
import { resolveOffset } from './offset.mjs';
import { ScrollOffset } from './presets.mjs';

/**
 * Resolved offsets map to evenly spaced progress values, so progress is
 * derived from the segment index rather than building an interpolator.
 */
function offsetsToProgress(offsets, v) {
    const n = offsets.length - 1;
    if (n < 1)
        return 0;
    const reverse = offsets[0] > offsets[n];
    const at = (i) => offsets[reverse ? n - i : i];
    /**
     * Matches interpolate(), which checks for a zero-length first range
     * before reversing descending offsets.
     */
    if (offsets[0] === offsets[1] && v < at(0))
        return reverse ? 1 : 0;
    let i = 0;
    while (i < n - 1 && v >= at(i + 1))
        i++;
    const p = (i + progress(at(i), at(i + 1), v)) / n;
    return reverse ? 1 - p : p;
}
function resolveOffsets(info, options) {
    const { offset: offsetDefinition = ScrollOffset.All, axis = "y" } = options;
    const axisInfo = info[axis];
    /**
     * Reset the length of the resolved offset array rather than creating a new one.
     */
    axisInfo.offset.length = 0;
    /**
     * Populate the offset array by resolving the user's offset definition into
     * a list of pixel scroll offsets.
     */
    const numOffsets = offsetDefinition.length;
    for (let i = 0; i < numOffsets; i++) {
        axisInfo.offset[i] = resolveOffset(offsetDefinition[i], axisInfo.containerLength, axisInfo.targetLength, axisInfo.targetOffset);
    }
    axisInfo.progress = clamp(0, 1, offsetsToProgress(axisInfo.offset, axisInfo.current));
}

export { resolveOffsets };
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