export async function saveSharedConfigFile()

in server/aws-lsp-identity/src/sharedConfig/saveSharedConfigFile.ts [12:93]
53 lines of code
14 McCabe index (conditional complexity)

export async function saveSharedConfigFile(
    filepath: string,
    filetype: IniFileType,
    file: ParsedIniData
): Promise<void> {
    const output: string[] = []
    const filepathExists = fs.existsSync(filepath)

    if (filepathExists) {
        // Be tolerant of line terminator in file regardless of OS
        const input = (await readFile(filepath, { encoding: 'utf-8' })).split(/\r?\n/)

        for (let it = new IniFileIterator(input.values(), output), { done, value } = it.nextSectionHeader(); !done; ) {
            if (!value) {
                continue
            }

            // Write updated section
            const parsedSectionName = value.toParsedSectionName()
            const newSettingsIndices: Record<string, number> = {}
            if (file[parsedSectionName] && Object.keys(file[parsedSectionName]).length > 0) {
                const fileSection = file[parsedSectionName]
                newSettingsIndices[sectionHeaderKey] = output.push(value.toIniSectionName(filetype))

                // Remove/update settings in file based on in-memory section
                ;({ done, value } = it.nextSectionHeader((setting: Setting) => {
                    const parsedSettingName = setting.toParsedSettingName()

                    // If setting in file, but not in-memory then skip it (it's been deleted)
                    if (!fileSection[parsedSettingName]) {
                        return
                    }

                    // Otherwise, update setting in file regardless
                    setting.value = fileSection[parsedSettingName]

                    // Done with this setting, delete so that only new settings are left at the end of the loop
                    // This also prevents writing redundant settings in the same section
                    delete fileSection[parsedSettingName]

                    if (setting.subsection && !newSettingsIndices[setting.subsection]) {
                        newSettingsIndices[setting.subsection] = output.push(setting.toIniSubsectionHeaderLine())
                    }

                    newSettingsIndices[nextSettingKey] = output.push(setting.toIniSettingLine())
                }))

                // Insert remaining settings (i.e. new settings) after last setting written or under section header
                // to avoid splitting settings across commented out sections at the end (which may be a commented out section itself)
                outputNewSettings(fileSection, newSettingsIndices, output)
            } else {
                // Delete no longer existing section by not emitting anything until the next section header is read
                // eslint-disable-next-line no-extra-semi
                ;({ done, value } = it.nextSectionHeader())
            }

            // Delete processed sections from file so only new sections in file are left at the end of this loop
            delete file[parsedSectionName]
        }
    }

    // Add remaining sections (i.e. new sections) to the end of the file
    for (const [parsedSectionName, parsedSectionSettings] of Object.entries(file).sort(compareObjectEntries)) {
        if (parsedSectionName && parsedSectionSettings && Object.keys(parsedSectionSettings).length > 0) {
            const newSettingsIndices: Record<string, number> = {}

            output.push('') // Empty line
            newSettingsIndices[sectionHeaderKey] = output.push(
                SectionHeader.fromParsedSectionName(parsedSectionName).toIniSectionName(filetype)
            )
            outputNewSettings(parsedSectionSettings, newSettingsIndices, output)
        }
    }

    // Backup file just in case
    if (filepathExists) {
        await rename(filepath, filepath + '~')
    }

    await mkdir(path.dirname(filepath), { mode: 0o755, recursive: true })
    await writeFile(filepath, output.join(EOL), { encoding: 'utf-8', flush: true })
}