import { test, expect } from "bun:test"
import { VM } from "#vm"
import { OpCode } from "#opcode"

test("MAKE_FUNCTION - creates function with captured scope", async () => {
  const vm = new VM({
    instructions: [
      { op: OpCode.MAKE_FUNCTION, operand: 0 }
    ],
    constants: [
      {
        type: 'function_def',
        params: [],
        defaults: {},
        body: 999,
        variadic: false,
        kwargs: false
      }
    ]
  })

  const result = await vm.run()
  expect(result.type).toBe('function')
  if (result.type === 'function') {
    expect(result.body).toBe(999)
    expect(result.params).toEqual([])
  }
})

test("CALL and RETURN - basic function call", async () => {
  // Function that returns 42
  const vm = new VM({
    instructions: [
      // 0: Create and call the function
      { op: OpCode.MAKE_FUNCTION, operand: 0 },
      { op: OpCode.CALL, operand: 0 },  // call with 0 args
      { op: OpCode.HALT },

      // 3: Function body (starts here, address = 3)
      { op: OpCode.PUSH, operand: 1 },  // push 42
      { op: OpCode.RETURN }
    ],
    constants: [
      {
        type: 'function_def',
        params: [],
        defaults: {},
        body: 3,  // function body starts at instruction 3
        variadic: false,
        kwargs: false
      },
      { type: 'number', value: 42 }
    ]
  })

  const result = await vm.run()
  expect(result).toEqual({ type: 'number', value: 42 })
})

test("CALL and RETURN - function with one parameter", async () => {
  // Function that returns its parameter
  const vm = new VM({
    instructions: [
      // 0: Push argument and call function
      { op: OpCode.MAKE_FUNCTION, operand: 0 },
      { op: OpCode.PUSH, operand: 1 },  // argument: 100
      { op: OpCode.CALL, operand: 1 },  // call with 1 arg
      { op: OpCode.HALT },

      // 4: Function body
      { op: OpCode.LOAD, operand: 'x' },  // load parameter x
      { op: OpCode.RETURN }
    ],
    constants: [
      {
        type: 'function_def',
        params: ['x'],
        defaults: {},
        body: 4,
        variadic: false,
        kwargs: false
      },
      { type: 'number', value: 100 }
    ]
  })

  const result = await vm.run()
  expect(result).toEqual({ type: 'number', value: 100 })
})

test("CALL and RETURN - function with two parameters", async () => {
  // Function that adds two parameters
  const vm = new VM({
    instructions: [
      // 0: Push arguments and call function
      { op: OpCode.MAKE_FUNCTION, operand: 0 },
      { op: OpCode.PUSH, operand: 1 },  // arg1: 10
      { op: OpCode.PUSH, operand: 2 },  // arg2: 20
      { op: OpCode.CALL, operand: 2 },  // call with 2 args
      { op: OpCode.HALT },

      // 5: Function body
      { op: OpCode.LOAD, operand: 'a' },
      { op: OpCode.LOAD, operand: 'b' },
      { op: OpCode.ADD },
      { op: OpCode.RETURN }
    ],
    constants: [
      {
        type: 'function_def',
        params: ['a', 'b'],
        defaults: {},
        body: 5,
        variadic: false,
        kwargs: false
      },
      { type: 'number', value: 10 },
      { type: 'number', value: 20 }
    ]
  })

  const result = await vm.run()
  expect(result).toEqual({ type: 'number', value: 30 })
})