import {
  ILookaheadStrategy,
  ILookaheadValidationError,
  IOrAlt,
  Rule,
  TokenType,
  OptionalProductionType
} from "@chevrotain/types"
import flatMap from "lodash/flatMap"
import isEmpty from "lodash/isEmpty"
import { defaultGrammarValidatorErrorProvider } from "../errors_public"
import { DEFAULT_PARSER_CONFIG } from "../parser/parser"
import {
  validateAmbiguousAlternationAlternatives,
  validateEmptyOrAlternative,
  validateNoLeftRecursion,
  validateSomeNonEmptyLookaheadPath
} from "./checks"
import {
  buildAlternativesLookAheadFunc,
  buildLookaheadFuncForOptionalProd,
  buildLookaheadFuncForOr,
  buildSingleAlternativeLookaheadFunction,
  getProdType
} from "./lookahead"
import { IParserDefinitionError } from "./types"

export class LLkLookaheadStrategy implements ILookaheadStrategy {
  readonly maxLookahead: number

  constructor(options?: { maxLookahead?: number }) {
    this.maxLookahead =
      options?.maxLookahead ?? DEFAULT_PARSER_CONFIG.maxLookahead
  }

  validate(options: {
    rules: Rule[]
    tokenTypes: TokenType[]
    grammarName: string
  }): ILookaheadValidationError[] {
    const leftRecursionErrors = this.validateNoLeftRecursion(options.rules)

    if (isEmpty(leftRecursionErrors)) {
      const emptyAltErrors = this.validateEmptyOrAlternatives(options.rules)
      const ambiguousAltsErrors = this.validateAmbiguousAlternationAlternatives(
        options.rules,
        this.maxLookahead
      )
      const emptyRepetitionErrors = this.validateSomeNonEmptyLookaheadPath(
        options.rules,
        this.maxLookahead
      )
      const allErrors = [
        ...leftRecursionErrors,
        ...emptyAltErrors,
        ...ambiguousAltsErrors,
        ...emptyRepetitionErrors
      ]
      return allErrors
    }
    return leftRecursionErrors
  }

  validateNoLeftRecursion(rules: Rule[]): IParserDefinitionError[] {
    return flatMap(rules, (currTopRule) =>
      validateNoLeftRecursion(
        currTopRule,
        currTopRule,
        defaultGrammarValidatorErrorProvider
      )
    )
  }

  validateEmptyOrAlternatives(rules: Rule[]): IParserDefinitionError[] {
    return flatMap(rules, (currTopRule) =>
      validateEmptyOrAlternative(
        currTopRule,
        defaultGrammarValidatorErrorProvider
      )
    )
  }

  validateAmbiguousAlternationAlternatives(
    rules: Rule[],
    maxLookahead: number
  ): IParserDefinitionError[] {
    return flatMap(rules, (currTopRule) =>
      validateAmbiguousAlternationAlternatives(
        currTopRule,
        maxLookahead,
        defaultGrammarValidatorErrorProvider
      )
    )
  }

  validateSomeNonEmptyLookaheadPath(
    rules: Rule[],
    maxLookahead: number
  ): IParserDefinitionError[] {
    return validateSomeNonEmptyLookaheadPath(
      rules,
      maxLookahead,
      defaultGrammarValidatorErrorProvider
    )
  }

  buildLookaheadForAlternation(options: {
    prodOccurrence: number
    rule: Rule
    maxLookahead: number
    hasPredicates: boolean
    dynamicTokensEnabled: boolean
  }): (orAlts?: IOrAlt<any>[] | undefined) => number | undefined {
    return buildLookaheadFuncForOr(
      options.prodOccurrence,
      options.rule,
      options.maxLookahead,
      options.hasPredicates,
      options.dynamicTokensEnabled,
      buildAlternativesLookAheadFunc
    )
  }

  buildLookaheadForOptional(options: {
    prodOccurrence: number
    prodType: OptionalProductionType
    rule: Rule
    maxLookahead: number
    dynamicTokensEnabled: boolean
  }): () => boolean {
    return buildLookaheadFuncForOptionalProd(
      options.prodOccurrence,
      options.rule,
      options.maxLookahead,
      options.dynamicTokensEnabled,
      getProdType(options.prodType),
      buildSingleAlternativeLookaheadFunction
    )
  }
}