import { describe, expect, it } from 'vitest'
import { ParquetType } from '../src/constants.js'
import { readPlain } from '../src/encoding.js'

describe('readPlain', () => {

  it('reads BOOLEAN values correctly', () => {
    const dataView = new DataView(new ArrayBuffer(1))
    dataView.setUint8(0, 0b00000001) // Set the first bit to 1
    const result = readPlain(dataView, ParquetType.BOOLEAN, 1, 0)
    expect(result).toEqual({ value: [true], byteLength: 1 })
  })

  it('reads INT32 values correctly', () => {
    const dataView = new DataView(new ArrayBuffer(4))
    dataView.setInt32(0, 123456789, true) // little-endian
    const result = readPlain(dataView, ParquetType.INT32, 1, 0)
    expect(result).toEqual({ value: [123456789], byteLength: 4 })
  })

  it('reads INT64 values correctly', () => {
    const dataView = new DataView(new ArrayBuffer(8))
    dataView.setBigInt64(0, BigInt('1234567890123456789'), true)
    const result = readPlain(dataView, ParquetType.INT64, 1, 0)
    expect(result).toEqual({ value: [1234567890123456789n], byteLength: 8 })
  })

  it('reads INT96 values correctly', () => {
    const buffer = new ArrayBuffer(12) // 12 bytes for a single INT96 value
    const dataView = new DataView(buffer)

    // Example INT96 value split into 64-bit low part and 32-bit high part
    const low = BigInt('0x0123456789ABCDEF')
    const high = 0x02345678
    dataView.setBigInt64(0, low, true)
    dataView.setInt32(8, high, true)
    const expectedValue = (BigInt(high) << BigInt(32)) | low

    const result = readPlain(dataView, ParquetType.INT96, 1, 0)
    expect(result).toEqual({
      value: [expectedValue],
      byteLength: 12,
    })
  })

  it('reads FLOAT values correctly', () => {
    const dataView = new DataView(new ArrayBuffer(4))
    dataView.setFloat32(0, 1234.5, true) // little-endian
    const result = readPlain(dataView, ParquetType.FLOAT, 1, 0)
    expect(result).toEqual({ value: [1234.5], byteLength: 4 })
  })

  it('reads DOUBLE values correctly', () => {
    const dataView = new DataView(new ArrayBuffer(8))
    dataView.setFloat64(0, 12345.6789, true) // little-endian
    const result = readPlain(dataView, ParquetType.DOUBLE, 1, 0)
    expect(result).toEqual({ value: [12345.6789], byteLength: 8 })
  })

  it('reads BYTE_ARRAY values correctly', () => {
    const dataView = new DataView(new ArrayBuffer(10))
    dataView.setInt32(0, 3, true) // length of the first byte array
    dataView.setUint8(4, 1) // first byte array data
    dataView.setUint8(5, 2)
    dataView.setUint8(6, 3)
    const result = readPlain(dataView, ParquetType.BYTE_ARRAY, 1, 0)
    expect(result).toEqual({
      value: [new Uint8Array([1, 2, 3])],
      byteLength: 7,
    })
  })

  it('reads FIXED_LEN_BYTE_ARRAY values correctly', () => {
    const fixedLength = 3
    const dataView = new DataView(new ArrayBuffer(fixedLength))
    dataView.setUint8(0, 4)
    dataView.setUint8(1, 5)
    dataView.setUint8(2, 6)
    const result = readPlain(dataView, ParquetType.FIXED_LEN_BYTE_ARRAY, fixedLength, 0)
    expect(result).toEqual({
      value: new Uint8Array([4, 5, 6]),
      byteLength: fixedLength,
    })
  })

  it('throws an error for unhandled types', () => {
    const dataView = new DataView(new ArrayBuffer(0))
    const invalidType = 999
    expect(() => readPlain(dataView, invalidType, 1, 0)).toThrow(`Unhandled type: ${invalidType}`)
  })
})