shrimp/src/compiler/compiler.ts

import { CompilerError } from '#compiler/compilerError.ts'
import { parse } from '#parser/parser2'
import { SyntaxNode, Tree } from '#parser/node'
import { parser } from '#parser/shrimp.ts'
import * as terms from '#parser/shrimp.terms'
import { setGlobals } from '#parser/tokenizer'
import { tokenizeCurlyString } from '#parser/curlyTokenizer'
import { assert, errorMessage } from '#utils/utils'
import { toBytecode, type Bytecode, type ProgramItem, bytecodeToString } from 'reefvm'
import {
  checkTreeForErrors,
  getAllChildren,
  getAssignmentParts,
  getCompoundAssignmentParts,
  getBinaryParts,
  getDotGetParts,
  getFunctionCallParts,
  getFunctionDefParts,
  getIfExprParts,
  getNamedArgParts,
  getPipeExprParts,
  getStringParts,
  getTryExprParts,
} from '#compiler/utils'

const DEBUG = false
// const DEBUG = true

type Label = `.${string}`

// Process escape sequences in strings
function processEscapeSeq(escapeSeq: string): string {
  // escapeSeq includes the backslash, e.g., "\n", "\$", "\\"
  if (escapeSeq.length !== 2) return escapeSeq

  switch (escapeSeq[1]) {
    case 'n':
      return '\n'
    case 't':
      return '\t'
    case 'r':
      return '\r'
    case '\\':
      return '\\'
    case "'":
      return "'"
    case '$':
      return '$'
    default:
      return escapeSeq // Unknown escape, keep as-is
  }
}

export class Compiler {
  instructions: ProgramItem[] = []
  labelCount = 0
  fnLabelCount = 0
  ifLabelCount = 0
  tryLabelCount = 0
  loopLabelCount = 0
  bytecode: Bytecode
  pipeCounter = 0

  constructor(public input: string, globals?: string[] | Record<string, any>) {
    try {
      if (globals) setGlobals(Array.isArray(globals) ? globals : Object.keys(globals))
      const ast = parse(input)
      const cst = new Tree(ast)
      const errors = checkTreeForErrors(cst)

      const firstError = errors[0]
      if (firstError) {
        throw firstError
      }

      this.#compileCst(cst, input)
      this.bytecode = toBytecode(this.instructions)

      if (DEBUG) {
        const bytecodeString = bytecodeToString(this.bytecode)
        console.log(`\n🤖 bytecode:\n----------------\n${bytecodeString}\n\n`)
        console.log(`\n🤖 bytecode:\n----------------\n${this.instructions}\n\n`)
      }
    } catch (error) {
      if (error instanceof CompilerError) {
        throw new Error(error.toReadableString(input))
      } else {
        throw new Error(`Unknown error during compilation:\n${errorMessage(error)}`)
      }
    }
  }

  #compileCst(cst: Tree, input: string) {
    const isProgram = cst.topNode.type.id === terms.Program
    assert(isProgram, `Expected Program node, got ${cst.topNode.type.name}`)

    let child = cst.topNode.firstChild
    while (child) {
      this.instructions.push(...this.#compileNode(child, input))
      child = child.nextSibling
    }

    this.instructions.push(['HALT'])
  }

  #compileNode(node: SyntaxNode, input: string): ProgramItem[] {
    const value = input.slice(node.from, node.to)
    if (DEBUG) console.log(`🫦  ${node.name}: ${value}`)

    switch (node.type.id) {
      case terms.Number:
        // Handle sign prefix for hex, binary, and octal literals
        // Number() doesn't parse '-0xFF', '+0xFF', '-0o77', etc. correctly
        let numberValue: number
        if (value.startsWith('-') && (value.includes('0x') || value.includes('0b') || value.includes('0o'))) {
          numberValue = -Number(value.slice(1))
        } else if (value.startsWith('+') && (value.includes('0x') || value.includes('0b') || value.includes('0o'))) {
          numberValue = Number(value.slice(1))
        } else {
          numberValue = Number(value)
        }

        if (Number.isNaN(numberValue))
          throw new CompilerError(`Invalid number literal: ${value}`, node.from, node.to)

        return [[`PUSH`, numberValue]]

      case terms.String: {
        if (node.firstChild?.type.id === terms.CurlyString)
          return this.#compileCurlyString(value, input)

        const { parts, hasInterpolation } = getStringParts(node, input)

        // Simple string without interpolation or escapes - extract text directly
        if (!hasInterpolation) {
          // Remove surrounding quotes and return as-is
          const strValue = value.slice(1, -1)
          return [['PUSH', strValue]]
        }

        // String with interpolation or escapes - compile each part and concatenate
        const instructions: ProgramItem[] = []
        parts.forEach((part) => {
          const partValue = input.slice(part.from, part.to)

          switch (part.type.id) {
            case terms.StringFragment:
              // Plain text fragment - just push as-is
              instructions.push(['PUSH', partValue])
              break

            case terms.EscapeSeq:
              // Process escape sequence and push the result
              const processed = processEscapeSeq(partValue)
              instructions.push(['PUSH', processed])
              break

            case terms.Interpolation:
              // Interpolation contains either Identifier or ParenExpr (the $ is anonymous)
              const child = part.firstChild
              if (!child) {
                throw new CompilerError('Interpolation has no child', part.from, part.to)
              }
              // Compile the Identifier or ParenExpr
              instructions.push(...this.#compileNode(child, input))
              break

            default:
              throw new CompilerError(
                `Unexpected string part: ${part.type.name}`,
                part.from,
                part.to
              )
          }
        })

        // Use STR_CONCAT to join all parts
        instructions.push(['STR_CONCAT', parts.length])
        return instructions
      }

      case terms.Boolean: {
        return [[`PUSH`, value === 'true']]
      }

      case terms.Null: {
        return [[`PUSH`, null]]
      }

      case terms.Regex: {
        // remove the surrounding slashes and any flags
        const [_, pattern, flags] = value.match(/^\/\/(.*)\/\/([gimsuy]*)$/) || []
        if (!pattern) {
          throw new CompilerError(`Invalid regex literal: ${value}`, node.from, node.to)
        }
        let regex: RegExp

        try {
          regex = new RegExp(pattern, flags)
        } catch (e) {
          throw new CompilerError(`Invalid regex literal: ${value}`, node.from, node.to)
        }

        return [['PUSH', regex]]
      }

      case terms.Identifier: {
        return [[`TRY_LOAD`, value]]
      }

      case terms.Word: {
        return [['PUSH', value]]
      }

      case terms.DotGet: {
        // DotGet is parsed into a nested tree because it's hard to parse it into a flat one.
        // However, we want a flat tree - so we're going to pretend like we are getting one from the parser.
        //
        //    This: DotGet(config, DotGet(script, name))
        // Becomes: DotGet(config, script, name)
        const { objectName, property } = getDotGetParts(node, input)
        const instructions: ProgramItem[] = []

        instructions.push(['TRY_LOAD', objectName])

        const flattenProperty = (prop: SyntaxNode): void => {
          if (prop.type.id === terms.DotGet) {
            const nestedParts = getDotGetParts(prop, input)

            const nestedObjectValue = input.slice(nestedParts.object.from, nestedParts.object.to)
            instructions.push(['PUSH', nestedObjectValue])
            instructions.push(['DOT_GET'])

            flattenProperty(nestedParts.property)
          } else {
            if (prop.type.id === terms.ParenExpr) {
              instructions.push(...this.#compileNode(prop, input))
            } else {
              const propertyValue = input.slice(prop.from, prop.to)
              instructions.push(['PUSH', propertyValue])
            }
            instructions.push(['DOT_GET'])
          }
        }

        flattenProperty(property)
        return instructions
      }

      case terms.BinOp: {
        const { left, op, right } = getBinaryParts(node)
        const instructions: ProgramItem[] = []
        instructions.push(...this.#compileNode(left, input))
        instructions.push(...this.#compileNode(right, input))

        const opValue = input.slice(op.from, op.to)
        switch (opValue) {
          case '+':
            instructions.push(['ADD'])
            break
          case '-':
            instructions.push(['SUB'])
            break
          case '*':
            instructions.push(['MUL'])
            break
          case '/':
            instructions.push(['DIV'])
            break
          case '%':
            instructions.push(['MOD'])
            break
          case 'band':
            instructions.push(['BIT_AND'])
            break
          case 'bor':
            instructions.push(['BIT_OR'])
            break
          case 'bxor':
            instructions.push(['BIT_XOR'])
            break
          case '<<':
            instructions.push(['BIT_SHL'])
            break
          case '>>':
            instructions.push(['BIT_SHR'])
            break
          case '>>>':
            instructions.push(['BIT_USHR'])
            break
          default:
            throw new CompilerError(`Unsupported binary operator: ${opValue}`, op.from, op.to)
        }

        return instructions
      }

      case terms.Assign: {
        const assignParts = getAssignmentParts(node)
        const instructions: ProgramItem[] = []

        // right-hand side
        instructions.push(...this.#compileNode(assignParts.right, input))

        // array destructuring: [ a b ] = [ 1 2 3 4 ]
        if ('arrayPattern' in assignParts) {
          const identifiers = assignParts.arrayPattern ?? []
          if (identifiers.length === 0) return instructions

          for (let i = 0; i < identifiers.length; i++) {
            instructions.push(['DUP'])
            instructions.push(['PUSH', i])
            instructions.push(['DOT_GET'])
            instructions.push(['STORE', input.slice(identifiers[i]!.from, identifiers[i]!.to)])
          }

          // original array still on stack as the return value
          return instructions
        }

        // simple assignment: x = value
        instructions.push(['DUP'])
        const identifierName = input.slice(assignParts.identifier.from, assignParts.identifier.to)
        instructions.push(['STORE', identifierName])

        return instructions
      }

      case terms.CompoundAssign: {
        const { identifier, operator, right } = getCompoundAssignmentParts(node)
        const identifierName = input.slice(identifier.from, identifier.to)
        const instructions: ProgramItem[] = []
        const opValue = input.slice(operator.from, operator.to)

        // Special handling for ??= since it needs conditional evaluation
        if (opValue === '??=') {
          instructions.push(['LOAD', identifierName])

          const skipLabel: Label = `.skip_${this.labelCount++}`
          const rightInstructions = this.#compileNode(right, input)

          instructions.push(['DUP'])
          instructions.push(['PUSH', null])
          instructions.push(['NEQ'])
          instructions.push(['JUMP_IF_TRUE', skipLabel])
          instructions.push(['POP'])
          instructions.push(...rightInstructions)

          instructions.push([`${skipLabel}:`])
          instructions.push(['DUP'])
          instructions.push(['STORE', identifierName])

          return instructions
        }

        // Standard compound assignments: evaluate both sides, then operate
        instructions.push(['LOAD', identifierName])  // will throw if undefined
        instructions.push(...this.#compileNode(right, input))

        switch (opValue) {
          case '+=':
            instructions.push(['ADD'])
            break
          case '-=':
            instructions.push(['SUB'])
            break
          case '*=':
            instructions.push(['MUL'])
            break
          case '/=':
            instructions.push(['DIV'])
            break
          case '%=':
            instructions.push(['MOD'])
            break
          default:
            throw new CompilerError(
              `Unknown compound operator: ${opValue}`,
              operator.from,
              operator.to
            )
        }

        // DUP and store (same as regular assignment)
        instructions.push(['DUP'])
        instructions.push(['STORE', identifierName])

        return instructions
      }

      case terms.ParenExpr: {
        const child = node.firstChild
        if (!child) return [] // I guess it is empty parentheses?

        return this.#compileNode(child, input)
      }

      case terms.FunctionDef: {
        const { paramNames, bodyNodes, catchVariable, catchBody, finallyBody } =
          getFunctionDefParts(node, input)
        const instructions: ProgramItem[] = []
        const functionLabel: Label = `.func_${this.fnLabelCount++}`
        const afterLabel: Label = `.after_${functionLabel}`

        instructions.push(['JUMP', afterLabel])

        instructions.push([`${functionLabel}:`])

        const compileFunctionBody = () => {
          const bodyInstructions: ProgramItem[] = []
          bodyNodes.forEach((bodyNode, index) => {
            bodyInstructions.push(...this.#compileNode(bodyNode, input))
            if (index < bodyNodes.length - 1) {
              bodyInstructions.push(['POP'])
            }
          })
          return bodyInstructions
        }

        if (catchVariable || finallyBody) {
          // If function has catch or finally, wrap body in try/catch/finally
          instructions.push(
            ...this.#compileTryCatchFinally(
              compileFunctionBody,
              catchVariable,
              catchBody,
              finallyBody,
              input
            )
          )
        } else {
          instructions.push(...compileFunctionBody())
        }

        instructions.push(['RETURN'])

        instructions.push([`${afterLabel}:`])

        instructions.push(['MAKE_FUNCTION', paramNames, functionLabel])

        return instructions
      }

      case terms.FunctionCallOrIdentifier: {
        if (node.firstChild?.type.id === terms.DotGet) {
          const instructions: ProgramItem[] = []
          const callLabel: Label = `.call_dotget_${++this.labelCount}`
          const afterLabel: Label = `.after_dotget_${++this.labelCount}`

          instructions.push(...this.#compileNode(node.firstChild, input))
          instructions.push(['DUP'])
          instructions.push(['TYPE'])
          instructions.push(['PUSH', 'function'])
          instructions.push(['EQ'])
          instructions.push(['JUMP_IF_TRUE', callLabel])
          instructions.push(['DUP'])
          instructions.push(['TYPE'])
          instructions.push(['PUSH', 'native'])
          instructions.push(['EQ'])
          instructions.push(['JUMP_IF_TRUE', callLabel])
          instructions.push(['JUMP', afterLabel])
          instructions.push([`${callLabel}:`])
          instructions.push(['PUSH', 0])
          instructions.push(['PUSH', 0])
          instructions.push(['CALL'])
          instructions.push([`${afterLabel}:`])

          return instructions
        }

        return [['TRY_CALL', value]]
      }

      /*
      ### Function Calls
      Stack order (bottom to top):

      LOAD fn
      PUSH arg1           ; Positional args
      PUSH arg2
      PUSH "name"         ; Named arg key
      PUSH "value"        ; Named arg value
      PUSH 2              ; Positional count
      PUSH 1              ; Named count
      CALL
      */
      case terms.FunctionCallWithNewlines:
      case terms.FunctionCall: {
        const { identifierNode, namedArgs, positionalArgs } = getFunctionCallParts(node, input)
        const instructions: ProgramItem[] = []
        instructions.push(...this.#compileNode(identifierNode, input))

        positionalArgs.forEach((arg) => {
          instructions.push(...this.#compileNode(arg, input))
        })

        namedArgs.forEach((arg) => {
          const { name, valueNode } = getNamedArgParts(arg, input)
          instructions.push(['PUSH', name])
          instructions.push(...this.#compileNode(valueNode, input))
        })

        instructions.push(['PUSH', positionalArgs.length])
        instructions.push(['PUSH', namedArgs.length])
        instructions.push(['CALL'])

        return instructions
      }

      case terms.Block: {
        const children = getAllChildren(node)
        const instructions: ProgramItem[] = []

        children.forEach((child, index) => {
          instructions.push(...this.#compileNode(child, input))
          // keep only the last expression's value
          if (index < children.length - 1) {
            instructions.push(['POP'])
          }
        })

        return instructions
      }

      case terms.FunctionCallWithBlock: {
        const [fn, _colon, ...block] = getAllChildren(node)
        let instructions: ProgramItem[] = []

        const fnLabel: Label = `.func_${this.fnLabelCount++}`
        const afterLabel: Label = `.after_${fnLabel}`

        instructions.push(['JUMP', afterLabel])
        instructions.push([`${fnLabel}:`])
        instructions.push(
          ...block
            .filter((x) => x.type.name !== 'keyword')
            .map((x) => this.#compileNode(x!, input))
            .flat()
        )
        instructions.push(['RETURN'])
        instructions.push([`${afterLabel}:`])

        if (fn?.type.id === terms.FunctionCallOrIdentifier) {
          instructions.push(['LOAD', input.slice(fn!.from, fn!.to)])
          instructions.push(['MAKE_FUNCTION', [], fnLabel])
          instructions.push(['PUSH', 1])
          instructions.push(['PUSH', 0])
          instructions.push(['CALL'])
        } else if (fn?.type.id === terms.FunctionCall) {
          let body = this.#compileNode(fn!, input)
          const namedArgCount = (body[body.length - 2]![1] as number) * 2
          const startSlice = body.length - namedArgCount - 3

          body = [
            ...body.slice(0, startSlice),
            ['MAKE_FUNCTION', [], fnLabel],
            ...body.slice(startSlice),
          ]

          // @ts-ignore
          body[body.length - 3]![1] += 1
          instructions.push(...body)
        } else {
          throw new Error(
            `FunctionCallWithBlock: Expected FunctionCallOrIdentifier or FunctionCall`
          )
        }

        return instructions
      }

      case terms.TryExpr: {
        const { tryBlock, catchVariable, catchBody, finallyBody } = getTryExprParts(node, input)

        return this.#compileTryCatchFinally(
          () => this.#compileNode(tryBlock, input),
          catchVariable,
          catchBody,
          finallyBody,
          input
        )
      }

      case terms.Throw: {
        const children = getAllChildren(node)
        const [_throwKeyword, expression] = children
        if (!expression) {
          throw new CompilerError(
            `Throw expected expression, got ${children.length} children`,
            node.from,
            node.to
          )
        }

        const instructions: ProgramItem[] = []
        instructions.push(...this.#compileNode(expression, input))
        instructions.push(['THROW'])

        return instructions
      }

      case terms.IfExpr: {
        const { conditionNode, thenBlock, elseIfBlocks, elseThenBlock } = getIfExprParts(
          node,
          input
        )
        const instructions: ProgramItem[] = []
        instructions.push(...this.#compileNode(conditionNode, input))
        this.ifLabelCount++
        const endLabel: Label = `.end_${this.ifLabelCount}`
        const elseLabel: Label = `.else_${this.ifLabelCount}`

        const thenBlockInstructions = this.#compileNode(thenBlock, input)
        instructions.push(['JUMP_IF_FALSE', elseLabel])
        instructions.push(...thenBlockInstructions)
        instructions.push(['JUMP', endLabel])

        instructions.push([`${elseLabel}:`])

        // Else if
        elseIfBlocks.forEach(({ conditional, thenBlock }, index) => {
          instructions.push(...this.#compileNode(conditional, input))
          const nextLabel: Label = `.elsif_${this.ifLabelCount}_${index}`
          const elseIfInstructions = this.#compileNode(thenBlock, input)
          instructions.push(['JUMP_IF_FALSE', nextLabel])
          instructions.push(...elseIfInstructions)
          instructions.push(['JUMP', endLabel])
          instructions.push([`${nextLabel}:`])
        })

        // Else
        if (elseThenBlock) {
          const elseThenInstructions = this.#compileNode(elseThenBlock, input)
          instructions.push(...elseThenInstructions)
        } else {
          instructions.push(['PUSH', null])
        }

        instructions.push([`${endLabel}:`])

        return instructions
      }

      // - `EQ`, `NEQ`, `LT`, `GT`, `LTE`, `GTE` - Pop 2, push boolean
      case terms.ConditionalOp: {
        const instructions: ProgramItem[] = []
        const { left, op, right } = getBinaryParts(node)
        const leftInstructions: ProgramItem[] = this.#compileNode(left, input)
        const rightInstructions: ProgramItem[] = this.#compileNode(right, input)

        const opValue = input.slice(op.from, op.to)
        switch (opValue) {
          case '==':
            instructions.push(...leftInstructions, ...rightInstructions, ['EQ'])
            break

          case '!=':
            instructions.push(...leftInstructions, ...rightInstructions, ['NEQ'])
            break

          case '<':
            instructions.push(...leftInstructions, ...rightInstructions, ['LT'])
            break

          case '>':
            instructions.push(...leftInstructions, ...rightInstructions, ['GT'])
            break

          case '<=':
            instructions.push(...leftInstructions, ...rightInstructions, ['LTE'])
            break

          case '>=':
            instructions.push(...leftInstructions, ...rightInstructions, ['GTE'])
            break

          case 'and': {
            const skipLabel: Label = `.skip_${this.labelCount++}`
            instructions.push(...leftInstructions)
            instructions.push(['DUP'])
            instructions.push(['JUMP_IF_FALSE', skipLabel])
            instructions.push(['POP'])
            instructions.push(...rightInstructions)
            instructions.push([`${skipLabel}:`])
            break
          }

          case 'or': {
            const skipLabel: Label = `.skip_${this.labelCount++}`
            instructions.push(...leftInstructions)
            instructions.push(['DUP'])
            instructions.push(['JUMP_IF_TRUE', skipLabel])
            instructions.push(['POP'])
            instructions.push(...rightInstructions)
            instructions.push([`${skipLabel}:`])
            break
          }

          case '??': {
            // Nullish coalescing: return left if not null, else right
            const skipLabel: Label = `.skip_${this.labelCount++}`
            instructions.push(...leftInstructions)
            instructions.push(['DUP'])
            instructions.push(['PUSH', null])
            instructions.push(['NEQ'])
            instructions.push(['JUMP_IF_TRUE', skipLabel])
            instructions.push(['POP'])
            instructions.push(...rightInstructions)
            instructions.push([`${skipLabel}:`])
            break
          }

          default:
            throw new CompilerError(`Unsupported conditional operator: ${opValue}`, op.from, op.to)
        }

        return instructions
      }

      case terms.PipeExpr: {
        const { pipedFunctionCall, pipeReceivers } = getPipeExprParts(node)
        if (!pipedFunctionCall || pipeReceivers.length === 0) {
          throw new CompilerError('PipeExpr must have at least two operands', node.from, node.to)
        }

        const instructions: ProgramItem[] = []
        instructions.push(...this.#compileNode(pipedFunctionCall, input))

        this.pipeCounter++
        const pipeValName = `_pipe_value_${this.pipeCounter}`
        pipeReceivers.forEach((pipeReceiver) => {
          instructions.push(['STORE', pipeValName])

          const { identifierNode, namedArgs, positionalArgs } = getFunctionCallParts(
            pipeReceiver,
            input
          )

          instructions.push(...this.#compileNode(identifierNode, input))

          const isUnderscoreInPositionalArgs = positionalArgs.some(
            (arg) => arg.type.id === terms.Underscore
          )
          const isUnderscoreInNamedArgs = namedArgs.some((arg) => {
            const { valueNode } = getNamedArgParts(arg, input)
            return valueNode.type.id === terms.Underscore
          })

          const shouldPushPositionalArg = !isUnderscoreInPositionalArgs && !isUnderscoreInNamedArgs

          // If no underscore is explicitly used, add the piped value as the first positional arg
          if (shouldPushPositionalArg) {
            instructions.push(['LOAD', pipeValName])
          }

          positionalArgs.forEach((arg) => {
            if (arg.type.id === terms.Underscore) {
              instructions.push(['LOAD', pipeValName])
            } else {
              instructions.push(...this.#compileNode(arg, input))
            }
          })

          namedArgs.forEach((arg) => {
            const { name, valueNode } = getNamedArgParts(arg, input)
            instructions.push(['PUSH', name])
            if (valueNode.type.id === terms.Underscore) {
              instructions.push(['LOAD', pipeValName])
            } else {
              instructions.push(...this.#compileNode(valueNode, input))
            }
          })

          instructions.push(['PUSH', positionalArgs.length + (shouldPushPositionalArg ? 1 : 0)])
          instructions.push(['PUSH', namedArgs.length])
          instructions.push(['CALL'])
        })

        return instructions
      }

      case terms.Array: {
        const children = getAllChildren(node)

        // We can easily parse [=] as an empty dict, but `[ = ]` is tougher.
        // = can be a valid word, and is also valid inside words, so for now we cheat
        // and check for arrays that look like `[ = ]` to interpret them as
        // empty dicts
        if (children.length === 1 && children[0]!.type.id === terms.Word) {
          const child = children[0]!
          if (input.slice(child.from, child.to) === '=') {
            return [['MAKE_DICT', 0]]
          }
        }

        const instructions: ProgramItem[] = children.map((x) => this.#compileNode(x, input)).flat()
        instructions.push(['MAKE_ARRAY', children.length])
        return instructions
      }

      case terms.Dict: {
        const children = getAllChildren(node)
        const instructions: ProgramItem[] = []

        children.forEach((node) => {
          const keyNode = node.firstChild
          const valueNode = node.firstChild!.nextSibling

          // name= -> name
          const key = input.slice(keyNode!.from, keyNode!.to).replace(/\s*=$/, '')
          instructions.push(['PUSH', key])

          instructions.push(...this.#compileNode(valueNode!, input))
        })

        instructions.push(['MAKE_DICT', children.length])
        return instructions
      }

      case terms.WhileExpr: {
        const [_while, test, _colon, block] = getAllChildren(node)
        const instructions: ProgramItem[] = []

        this.loopLabelCount++
        const startLoop = `.loop_${this.loopLabelCount}:`
        const endLoop = `.end_loop_${this.loopLabelCount}:`

        instructions.push([`${startLoop}:`])
        instructions.push(...this.#compileNode(test!, input))
        instructions.push(['JUMP_IF_FALSE', endLoop])
        instructions.push(...this.#compileNode(block!, input))
        instructions.push(['JUMP', startLoop])
        instructions.push([`${endLoop}:`])

        return instructions
      }

      case terms.Import: {
        const instructions: ProgramItem[] = []
        const [_import, ...nodes] = getAllChildren(node)
        const args = nodes.filter(node => node.type.id === terms.Identifier)
        const namedArgs = nodes.filter(node => node.type.id === terms.NamedArg)

        instructions.push(['LOAD', 'import'])

        args.forEach((dict) =>
          instructions.push(['PUSH', input.slice(dict.from, dict.to)])
        )

        namedArgs.forEach((arg) => {
          const { name, valueNode } = getNamedArgParts(arg, input)
          instructions.push(['PUSH', name])
          instructions.push(...this.#compileNode(valueNode, input))
        })

        instructions.push(['PUSH', args.length])
        instructions.push(['PUSH', namedArgs.length])
        instructions.push(['CALL'])

        return instructions
      }

      case terms.Comment: {
        return [] // ignore comments
      }

      default:
        throw new CompilerError(
          `Compiler doesn't know how to handle a "${node.type.name}" (${node.type.id}) node.`,
          node.from,
          node.to
        )
    }
  }

  #compileTryCatchFinally(
    compileTryBody: () => ProgramItem[],
    catchVariable: string | undefined,
    catchBody: SyntaxNode | undefined,
    finallyBody: SyntaxNode | undefined,
    input: string
  ): ProgramItem[] {
    const instructions: ProgramItem[] = []
    this.tryLabelCount++
    const catchLabel: Label = `.catch_${this.tryLabelCount}`
    const finallyLabel: Label = finallyBody ? `.finally_${this.tryLabelCount}` : (null as any)
    const endLabel: Label = `.end_try_${this.tryLabelCount}`

    instructions.push(['PUSH_TRY', catchLabel])
    instructions.push(...compileTryBody())
    instructions.push(['POP_TRY'])
    instructions.push(['JUMP', finallyBody ? finallyLabel : endLabel])

    // catch block
    instructions.push([`${catchLabel}:`])
    if (catchBody && catchVariable) {
      instructions.push(['STORE', catchVariable])
      const catchInstructions = this.#compileNode(catchBody, input)
      instructions.push(...catchInstructions)
      instructions.push(['JUMP', finallyBody ? finallyLabel : endLabel])
    } else {
      // no catch block
      if (finallyBody) {
        instructions.push(['JUMP', finallyLabel])
      } else {
        instructions.push(['THROW'])
      }
    }

    // finally block
    if (finallyBody) {
      instructions.push([`${finallyLabel}:`])
      const finallyInstructions = this.#compileNode(finallyBody, input)
      instructions.push(...finallyInstructions)
      // finally doesn't return a value
      instructions.push(['POP'])
    }

    instructions.push([`${endLabel}:`])

    return instructions
  }

  #compileCurlyString(value: string, input: string): ProgramItem[] {
    const instructions: ProgramItem[] = []
    const nodes = tokenizeCurlyString(value)

    nodes.forEach((node) => {
      if (typeof node === 'string') {
        instructions.push(['PUSH', node])
      } else {
        const [input, topNode] = node
        let child = topNode.firstChild
        while (child) {
          instructions.push(...this.#compileNode(child, input))
          child = child.nextSibling
        }
      }
    })

    instructions.push(['STR_CONCAT', nodes.length])

    return instructions
  }
}