import { isCompressed, decompressAsync, readHeaderAsync, readImage, hasExtension } from 'nifti-reader-js'
import { log } from '@/logger'
import type { NVImage } from '@/nvimage'
import { NiiDataType } from '@/nvimage/utils'

/**
 * Reads NIfTI format image (.nii, .nii.gz), modifying the provided NVImage header
 * and returning the raw image data buffer.
 * @param nvImage - The NVImage instance whose header will be modified.
 * @param buffer - ArrayBuffer containing the NIfTI file data.
 * @returns Promise resolving to the imgRaw ArrayBufferLike or null on critical error.
 */
export async function readNifti(nvImage: NVImage, buffer: ArrayBuffer, pairedImageData?: ArrayBuffer): Promise<ArrayBufferLike | null> {
    let dataBuffer = buffer // Work with a local variable
    let imgRaw: ArrayBufferLike | null = null

    try {
        if (isCompressed(dataBuffer as ArrayBuffer)) {
            log.debug(`Decompressing NIfTI file: ${nvImage.name}`) // Use name from nvImage instance
            dataBuffer = await decompressAsync(dataBuffer as ArrayBuffer)
            log.debug(`Decompression complete for: ${nvImage.name}`)
        }

        // Ensure buffer is still valid after potential decompression
        if (!dataBuffer || dataBuffer.byteLength === 0) {
            throw new Error('Buffer became invalid after decompression attempt.')
        }

        nvImage.hdr = await readHeaderAsync(dataBuffer as ArrayBuffer, pairedImageData != null)
        if (hasExtension(nvImage.hdr)) {
            nvImage.extensions = nvImage.hdr.extensions
        }

        if (nvImage.hdr === null) {
            throw new Error(`Failed to read NIfTI header: ${nvImage.name}`)
        }

        if (nvImage.hdr.cal_min === 0 && nvImage.hdr.cal_max === 255 && nvImage.hdr.datatypeCode !== NiiDataType.DT_UINT8) {
            log.debug(`Resetting suspicious cal_min/max (0/255) for non-uint8 NIfTI: ${nvImage.name}`)
            nvImage.hdr.cal_min = 0.0 // Use 0.0 to signal unset/recalculate later
            nvImage.hdr.cal_max = 0.0
        }

        imgRaw = pairedImageData ? readImage(nvImage.hdr, pairedImageData) : readImage(nvImage.hdr, dataBuffer as ArrayBuffer)

        if (imgRaw === null) {
            throw new Error(`nifti-reader-js readImage returned null for ${nvImage.name}`)
        }

        return imgRaw
    } catch (err) {
        log.error(`Error processing NIfTI file ${nvImage.name}:`, err)
        nvImage.hdr = null
        return null
    }
}