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michealrobertsmichealroberts
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Merge pull request #51 from observerly/feature/header/parseHeadersFromBlocks
feat: add parseHeadersFromBlocks to header module in @observerly/fits
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‎src/header/__tests__/parseHeadersFromBlocks.spec.ts‎

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/*****************************************************************************************************************/
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// @author Michael Roberts <michael@observerly.com>
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// @package @observerly/fits
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// @license Copyright © 2021-2023 observerly
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/*****************************************************************************************************************/
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import { describe, expect, it } from 'vitest'
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import type { FITSBlock } from '../../types'
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import { parseHeadersFromBlocks } from '../parseHeadersFromBlocks'
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/*****************************************************************************************************************/
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describe('parseHeadersFromBlocks', () => {
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it('should correctly parse standard headers without CONTINUE keys', () => {
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const blocks: FITSBlock[] = [
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{
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buffer: '...',
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headers: [
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{
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key: 'SIMPLE',
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value: true,
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comment: 'file conforms to FITS standard'
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},
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{
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key: 'BITPIX',
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value: 16,
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comment: 'number of bits per data pixel'
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},
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{
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key: 'NAXIS',
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value: 2,
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comment: 'number of data axes'
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}
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],
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offsetStart: 0,
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offsetEnd: 2880
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}
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]
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const headersMap = parseHeadersFromBlocks(blocks)
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expect(headersMap.size).toBe(3)
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expect(headersMap.get('SIMPLE')).toEqual({
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key: 'SIMPLE',
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value: true,
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comment: 'file conforms to FITS standard'
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})
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expect(headersMap.get('BITPIX')).toEqual({
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key: 'BITPIX',
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value: 16,
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comment: 'number of bits per data pixel'
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})
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expect(headersMap.get('NAXIS')).toEqual({
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key: 'NAXIS',
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value: 2,
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comment: 'number of data axes'
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})
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})
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it('should correctly handle CONTINUE keys by appending their values to the previous header', () => {
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const blocks: FITSBlock[] = [
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{
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buffer: '...',
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headers: [
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{
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key: 'COMMENT',
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value: 'This is a long comment that spans multiple',
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comment: 'initial part'
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},
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{
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key: 'CONTINUE',
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value: 'lines for better readability.',
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comment: 'continued part'
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},
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{
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key: 'END',
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value: true,
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comment: 'end of header'
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}
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],
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offsetStart: 0,
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offsetEnd: 2880
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}
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]
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const headersMap = parseHeadersFromBlocks(blocks)
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expect(headersMap.size).toBe(2)
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expect(headersMap.get('COMMENT')).toEqual({
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key: 'COMMENT',
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value: 'This is a long comment that spans multiple lines for better readability.',
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comment: 'initial part'
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})
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expect(headersMap.get('END')).toEqual({ key: 'END', value: true, comment: 'end of header' })
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})
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it('should handle multiple CONTINUE keys sequentially', () => {
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const blocks: FITSBlock[] = [
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{
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buffer: '...',
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headers: [
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{
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key: 'COMMENT',
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value: 'First part of the comment',
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comment: 'initial'
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},
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{
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key: 'CONTINUE',
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value: 'second part',
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comment: 'continued'
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},
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{
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key: 'CONTINUE',
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value: 'third part',
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comment: 'continued'
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},
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{
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key: 'BITPIX',
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value: -32,
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comment: 'number of bits per data pixel'
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}
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],
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offsetStart: 0,
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offsetEnd: 2880
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}
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]
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const headersMap = parseHeadersFromBlocks(blocks)
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expect(headersMap.size).toBe(2)
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expect(headersMap.get('COMMENT')).toEqual({
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key: 'COMMENT',
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value: 'First part of the comment second part third part',
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comment: 'initial'
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})
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expect(headersMap.get('BITPIX')).toEqual({
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key: 'BITPIX',
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value: -32,
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comment: 'number of bits per data pixel'
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})
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})
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it('should return an empty map when no headers are provided', () => {
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const blocks: FITSBlock[] = [
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{
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buffer: '...',
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headers: [],
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offsetStart: 0,
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offsetEnd: 2880
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}
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]
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const headersMap = parseHeadersFromBlocks(blocks)
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expect(headersMap.size).toBe(0)
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})
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it('should handle multiple blocks with overlapping headers and CONTINUE keys', () => {
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const blocks: FITSBlock[] = [
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{
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buffer: '...',
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headers: [
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{
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key: 'COMMENT',
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value: 'Block1 comment part1',
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comment: 'initial'
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},
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{
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key: 'CONTINUE',
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value: 'part2',
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comment: 'continued'
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}
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],
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offsetStart: 0,
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offsetEnd: 2880
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},
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{
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buffer: '...',
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headers: [
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{
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key: 'COMMENT',
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value: 'Block2 comment part1',
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comment: 'initial'
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},
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{
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key: 'CONTINUE',
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value: 'part2',
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comment: 'continued'
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}
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],
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offsetStart: 2880,
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offsetEnd: 5760
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}
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]
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const headersMap = parseHeadersFromBlocks(blocks)
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expect(headersMap.size).toBe(1)
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expect(headersMap.get('COMMENT')).toEqual({
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key: 'COMMENT',
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value: 'Block2 comment part1 part2',
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comment: 'initial'
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})
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})
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it('should ignore CONTINUE keys if there is no previous header', () => {
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const blocks: FITSBlock[] = [
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{
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buffer: '...',
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headers: [
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{
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key: 'CONTINUE',
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value: 'orphaned continue',
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comment: 'no previous header'
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},
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{
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key: 'BITPIX',
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value: 8,
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comment: 'number of bits per data pixel'
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}
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],
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offsetStart: 0,
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offsetEnd: 2880
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}
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]
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const headersMap = parseHeadersFromBlocks(blocks)
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expect(headersMap.size).toBe(1)
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expect(headersMap.get('BITPIX')).toEqual({
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key: 'BITPIX',
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value: 8,
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comment: 'number of bits per data pixel'
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})
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// The 'CONTINUE' key should be ignored as there is no previous header
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})
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})
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/*****************************************************************************************************************/

‎src/header/index.ts‎

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export { getFITSHeaders } from './getFITSHeaders'
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export { parseFITSHeaderBlock } from './parseFITSHeaderBlock'
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export { parseFITSHeaderRow } from './parseFITSHeaderRow'
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export { parseHeadersFromBlocks } from './parseHeadersFromBlocks'
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export { readFITSHeaderFromBlocks } from './readFITSHeaderFromBlocks'
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/*****************************************************************************************************************/

‎src/header/parseHeadersFromBlocks.ts‎

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/*****************************************************************************************************************/
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// @author Michael Roberts <michael@observerly.com>
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// @package @observerly/fits
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// @license Copyright © 2021-2023 observerly
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/*****************************************************************************************************************/
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import type { FITSBlock, FITSHeader } from '../types'
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/*****************************************************************************************************************/
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/**
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*
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* parseHeadersFromBlocks
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*
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* @param blocks - Array of FITS blocks to parse headers from
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* @returns Map of headers parsed from the blocks
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*/
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export const parseHeadersFromBlocks = (blocks: FITSBlock[]): Map<string, FITSHeader> => {
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const headers = new Map<string, FITSHeader>()
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// Flatten all headers from blocks into a single array
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const headerLines = blocks.flatMap(block => block.headers)
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// Keep track of the previous header for handling 'CONTINUE' keys
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let previousHeader: FITSHeader | null = null
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for (const header of headerLines) {
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if (header.key !== 'CONTINUE') {
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// Add the new header to the map and update the previous header reference
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headers.set(header.key, header)
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previousHeader = header
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} else if (previousHeader) {
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// Append 'CONTINUE' values to the previous header's value
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previousHeader.value += ` ${header.value}`
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}
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}
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return headers
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}
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/*****************************************************************************************************************/

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