import { Effect } from "effect"

import { AppFileSystem } from "@opencode-ai/core/filesystem"

const BOM_CODE = 0xfeff

const BOM = String.fromCharCode(BOM_CODE)

export function split(text: string) {

if (text.charCodeAt(0) !== BOM_CODE) return { bom: false, text }

return { bom: true, text: text.slice(1) }

}

export function join(text: string, bom: boolean) {

const stripped = split(text).text

if (!bom) return stripped

return BOM + stripped

}

export const readFile = Effect.fn("Bom.readFile")(function* (fs: AppFileSystem.Interface, filePath: string) {

return split(new TextDecoder("utf-8", { ignoreBOM: true }).decode(yield* fs.readFile(filePath)))

})

export const syncFile = Effect.fn("Bom.syncFile")(function* (

fs: AppFileSystem.Interface,

filePath: string,

bom: boolean,

) {

const current = yield* readFile(fs, filePath)

if (current.bom === bom) return current.text

yield* fs.writeWithDirs(filePath, join(current.text, bom))

return current.text

})