import { CompilerError } from '#compiler/compilerError.ts'
import { parser } from '#parser/shrimp.ts'
import * as terms from '#parser/shrimp.terms'
import type { SyntaxNode, Tree } from '@lezer/common'
import { assert, errorMessage } from '#utils/utils'
import { toBytecode, type Bytecode, type ProgramItem } from 'reefvm'
import {
  checkTreeForErrors,
  getAllChildren,
  getAssignmentParts,
  getBinaryParts,
  getFunctionCallParts,
  getFunctionDefParts,
  getIfExprParts,
  getNamedArgParts,
} from '#compiler/utils'

type Label = `.${string}`
export class Compiler {
  instructions: ProgramItem[] = []
  fnLabels = new Map<Label, ProgramItem[]>()
  ifLabelCount = 0
  bytecode: Bytecode

  constructor(public input: string) {
    try {
      const cst = parser.parse(input)
      const errors = checkTreeForErrors(cst, input)

      if (errors.length > 0) {
        throw new CompilerError(`Syntax errors found:\n${errors.join('\n')}`, 0, input.length)
      }

      this.#compileCst(cst, input)

      // Add the labels
      for (const [label, labelInstructions] of this.fnLabels) {
        this.instructions.push([`${label}:`])
        this.instructions.push(...labelInstructions)
        this.instructions.push(['RETURN'])
      }

      // logInstructions(this.instructions)

      this.bytecode = toBytecode(this.instructions)
    } 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)
    switch (node.type.id) {
      case terms.Number:
        const number = Number(value)
        if (Number.isNaN(number))
          throw new CompilerError(`Invalid number literal: ${value}`, node.from, node.to)

        return [[`PUSH`, number]]

      case terms.String:
        const strValue = value.slice(1, -1).replace(/\\/g, '')
        return [[`PUSH`, strValue]]

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

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

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

        return instructions
      }

      case terms.Assign: {
        const { identifier, right } = getAssignmentParts(node)
        const instructions: ProgramItem[] = []
        instructions.push(...this.#compileNode(right, input))
        const identifierName = input.slice(identifier.from, identifier.to)
        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, bodyNode } = getFunctionDefParts(node, input)
        const instructions: ProgramItem[] = []
        const functionLabel: Label = `.func_${this.fnLabels.size}`
        const bodyInstructions: ProgramItem[] = []
        if (this.fnLabels.has(functionLabel)) {
          throw new CompilerError(`Function name collision: ${functionLabel}`, node.from, node.to)
        }

        this.fnLabels.set(functionLabel, bodyInstructions)

        instructions.push(['MAKE_FUNCTION', paramNames, functionLabel])
        bodyInstructions.push(...this.#compileNode(bodyNode, input))

        return instructions
      }

      case terms.FunctionCallOrIdentifier: {
        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.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.ThenBlock: {
        const instructions = getAllChildren(node)
          .map((child) => this.#compileNode(child, input))
          .flat()

        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 thenBlockInstructions = this.#compileNode(thenBlock, input)
        instructions.push(['JUMP_IF_FALSE', thenBlockInstructions.length + 1])
        instructions.push(...thenBlockInstructions)
        instructions.push(['JUMP', endLabel])

        // Else if
        elseIfBlocks.forEach(({ conditional, thenBlock }) => {
          instructions.push(...this.#compileNode(conditional, input))
          const elseIfInstructions = this.#compileNode(thenBlock, input)
          instructions.push(['JUMP_IF_FALSE', elseIfInstructions.length + 1])
          instructions.push(...elseIfInstructions)
          instructions.push(['JUMP', endLabel])
        })

        // 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':
            instructions.push(...leftInstructions)
            instructions.push(['DUP'])
            instructions.push(['JUMP_IF_FALSE', rightInstructions.length + 1])
            instructions.push(['POP'])
            instructions.push(...rightInstructions)
            break

          case 'or':
            instructions.push(...leftInstructions)
            instructions.push(['DUP'])
            instructions.push(['JUMP_IF_TRUE', rightInstructions.length + 1])
            instructions.push(['POP'])
            instructions.push(...rightInstructions)

            break

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

        return instructions
      }

      case terms.PipeExpr: {
        const allChildren = getAllChildren(node)
        // Filter out the pipe operator nodes (they're just syntax)
        const operands = allChildren.filter((child) => child.type.name !== 'operator')
        if (operands.length < 2) {
          throw new CompilerError('PipeExpr must have at least two operands', node.from, node.to)
        }

        const instructions: ProgramItem[] = []

        // Compile first operand normally
        instructions.push(...this.#compileNode(operands[0]!, input))

        // For each subsequent operand, transform it to receive piped value as first arg
        for (let i = 1; i < operands.length; i++) {
          const operand = operands[i]!

          // Result from previous stage is on stack
          // We need to make it the first argument to the next call

          if (operand.type.id === terms.FunctionCallOrIdentifier) {
            // Simple identifier - emit TRY_CALL with piped value as single argument
            const identifierNode = operand.getChild('Identifier')
            if (!identifierNode) {
              throw new CompilerError('FunctionCallOrIdentifier must have Identifier', operand.from, operand.to)
            }
            const fnName = input.slice(identifierNode.from, identifierNode.to)

            // Stack has: [piped_value]
            // Store piped value temporarily
            instructions.push(['STORE', '__pipe_value'])

            // Load function
            instructions.push(['TRY_LOAD', fnName])

            // Load piped value as first arg
            instructions.push(['LOAD', '__pipe_value'])

            // Call with 1 positional arg and 0 named args
            instructions.push(['PUSH', 1])
            instructions.push(['PUSH', 0])
            instructions.push(['CALL'])

          } else if (operand.type.id === terms.FunctionCall) {
            // Function call with arguments - piped value becomes first argument
            const { identifierNode, namedArgs, positionalArgs } = getFunctionCallParts(operand, input)

            // Store piped value temporarily
            instructions.push(['STORE', '__pipe_value'])

            // Load function
            instructions.push(...this.#compileNode(identifierNode, input))

            // Push piped value as first arg
            instructions.push(['LOAD', '__pipe_value'])

            // Push remaining positional args
            positionalArgs.forEach((arg) => {
              instructions.push(...this.#compileNode(arg, input))
            })

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

            // Call with (positionalArgs + 1 for piped value) and namedArgs
            instructions.push(['PUSH', positionalArgs.length + 1])
            instructions.push(['PUSH', namedArgs.length])
            instructions.push(['CALL'])
          } else {
            throw new CompilerError(`Unsupported pipe operand type: ${operand.type.name}`, operand.from, operand.to)
          }
        }

        return instructions
      }

      default:
        throw new CompilerError(`Unsupported syntax node: ${node.type.name}`, node.from, node.to)
    }
  }
}

const logInstructions = (instructions: ProgramItem[]) => {
  const instructionsString = instructions
    .map((parts) => {
      const isPush = parts[0] === 'PUSH'
      return parts
        .map((part, i) => {
          const partAsString = typeof part == 'string' && isPush ? `'${part}'` : part!.toString()
          return i > 0 ? partAsString : part
        })
        .join(' ')
    })
    .join('\n')

  console.log(`\n🤖 instructions:\n----------------\n${instructionsString}\n\n`)
}