import * as Cause from "../../Cause.ts"
import * as Effect from "../../Effect.ts"
import type * as Exit from "../../Exit.ts"
import type * as Option from "../../Option.ts"
import * as SchemaAST from "../../SchemaAST.ts"
import * as SchemaIssue from "../../SchemaIssue.ts"
import type { Compiler, Parser } from "../../SchemaParser.ts"
import { effectIsExit } from "../effect.ts"
import * as InternalParser from "./parser.ts"

type ApplyTransformation = (
  result: Effect.Effect<unknown, SchemaIssue.Issue, unknown>,
  current: unknown,
  options: SchemaAST.ParseOptions
) => Effect.Effect<unknown, SchemaIssue.Issue, unknown>

const flatMapTransformation = (
  result: Effect.Effect<unknown, SchemaIssue.Issue, unknown>,
  current: unknown,
  f: (value: unknown) => Effect.Effect<unknown, SchemaIssue.Issue, unknown>
): Effect.Effect<unknown, SchemaIssue.Issue, unknown> =>
  result === InternalParser.sameExit ? f(current) : Effect.flatMapEager(result, f)

function compileTransformation(transformation: SchemaAST.Link["transformation"]): ApplyTransformation {
  if (transformation._tag === "Middleware") {
    return (result, current, options) => {
      const transformed = result === InternalParser.sameExit
        ? transformation.decode(InternalParser.succeed(InternalParser.toOption(current)), options)
        : transformation.decode(Effect.mapEager(result, InternalParser.toOption), options)
      return fromOptionalEffect(transformed)
    }
  }

  const getter = transformation.decode
  switch (getter._tag) {
    case "Passthrough":
      return (result, current) => result === InternalParser.sameExit ? InternalParser.succeed(current) : result
    case "Transform": {
      const transform = (value: unknown) =>
        value === InternalParser.missing
          ? InternalParser.missingExit
          : InternalParser.succeed(getter.transform(value))
      return (result, current) => flatMapTransformation(result, current, transform)
    }
    case "TransformOptional": {
      const transform = (value: unknown) =>
        InternalParser.fromOptionExit(getter.transform(InternalParser.toOption(value)))
      return (result, current) => flatMapTransformation(result, current, transform)
    }
    case "TransformEffect":
      return (result, current, options) =>
        flatMapTransformation(result, current, (value) =>
          value === InternalParser.missing
            ? InternalParser.missingExit
            : getter.transform(value, options))
    case "TransformOptionalEffect":
      return (result, current, options) =>
        flatMapTransformation(
          result,
          current,
          (value) => fromOptionalEffect(getter.transform(InternalParser.toOption(value), options))
        )
  }
}

const fromOptionalEffect = (
  effect: Effect.Effect<Option.Option<unknown>, SchemaIssue.Issue, unknown>
): Effect.Effect<unknown, SchemaIssue.Issue, unknown> => Effect.flatMapEager(effect, InternalParser.fromOptionExit)

/** @internal */
export const wrapEncoding = (
  ast: SchemaAST.AST,
  input: unknown,
  options: SchemaAST.ParseOptions,
  effect: Effect.Effect<unknown, SchemaIssue.Issue, unknown>
): Effect.Effect<unknown, SchemaIssue.Issue, unknown> =>
  Effect.catchCause(
    effect,
    (cause) =>
      Effect.failCauseSync(() => Cause.map(cause, (issue) => new SchemaIssue.Encoding(ast, issue, input, options)))
  )

function makeConstructorParser(descriptor: SchemaAST.ConstructorDescriptor, compile: Compiler): Parser {
  const transform = compileTransformation(descriptor.link.transformation)
  let sourceParser: Parser
  return (input, options) => {
    if (input === InternalParser.missing) return InternalParser.missingExit
    if (descriptor.isConstructed(input)) return InternalParser.sameExit
    const result = (sourceParser ??= compile(descriptor.link.to))(input, options)
    return transform(result, input, options)
  }
}

function withDefault(ast: SchemaAST.AST, parser: Parser): Parser {
  const defaultValue = ast.context!.constructorDefault!
  return (input, options) => {
    if (input !== InternalParser.missing && input !== undefined) return parser(input, options)
    const result = defaultValue
    if (effectIsExit(result) && result._tag === "Success") {
      const local = parser((result as InternalParser.Success<unknown>)[InternalParser.args], options)
      return local === InternalParser.sameExit ? result : local
    }
    return Effect.flatMapEager(
      wrapEncoding(ast, input, options, result),
      (value) => {
        const local = parser(value, options)
        return local === InternalParser.sameExit ? InternalParser.succeed(value) : local
      }
    )
  }
}

/** @internal */
export function compileField(ast: SchemaAST.AST, compile: Compiler): Parser {
  const parser = compile(ast)
  return ast.context?.constructorDefault === undefined ? parser : withDefault(ast, parser)
}

/** @internal */
export function compile(
  ast: SchemaAST.AST,
  compile: Compiler,
  compileField?: Compiler,
  base?: Parser,
  specialize?: (local: Parser) => Parser
): Parser {
  if (ast._tag === "Declaration") {
    // Declaration callbacks can create public parsers for their type parameters.
    // Register those ASTs with the same resolver before invoking the callback.
    for (const parameter of ast.typeParameters) compile(parameter)
  }
  // Construction supplies compileField for parent-owned defaults. Its presence
  // also selects the constructor semantics of declarations and Unions.
  const descriptor = compileField ? SchemaAST.getConstructorDescriptor(ast) : undefined
  const parser = descriptor
    ? makeConstructorParser(descriptor, compile)
    : base ?? ast.getParser(compile, compileField)
  const checks = ast.checks
  const links = ast.encoding
  const transformations = links?.map((link) => compileTransformation(link.transformation))
  const encodingChecks = (ast as any).encodingChecks
  if (!links && !checks && !encodingChecks) {
    return parser
  }
  let encodingParsers: ReadonlyArray<Parser> | undefined
  const parseChecks = (
    input: unknown,
    options: SchemaAST.ParseOptions
  ) => {
    let result = parser(input, options)
    if (encodingChecks && !options.disableChecks) {
      if (effectIsExit(result)) {
        if (result._tag === "Success") {
          const output = result === InternalParser.sameExit
            ? input
            : (result as InternalParser.Success<unknown, SchemaIssue.Issue>)[InternalParser.args]
          if (input !== InternalParser.missing && output !== InternalParser.missing) {
            const issues = SchemaAST.collectIssues(encodingChecks, input, undefined, ast, options)
            if (issues) {
              result = Effect.fail(new SchemaIssue.Composite(ast, issues, input, options))
            }
          }
        }
      } else {
        result = Effect.flatMap(result, (value) => {
          if (input !== InternalParser.missing && value !== InternalParser.missing) {
            const issues = SchemaAST.collectIssues(encodingChecks, input, undefined, ast, options)
            if (issues) {
              return Effect.fail(new SchemaIssue.Composite(ast, issues, input, options))
            }
          }
          return Effect.succeed(value)
        })
      }
    }

    if (checks && !options.disableChecks) {
      if (effectIsExit(result)) {
        if (result._tag === "Success") {
          const value = result === InternalParser.sameExit
            ? input
            : (result as InternalParser.Success<unknown, SchemaIssue.Issue>)[InternalParser.args]
          if (value === InternalParser.missing) return result
          const issues = SchemaAST.collectIssues(checks, value, undefined, ast, options)
          if (issues) {
            result = Effect.fail(new SchemaIssue.Composite(ast, issues, value, options))
          }
        }
      } else {
        result = Effect.flatMap(result, (value) => {
          if (value !== InternalParser.missing) {
            const issues = SchemaAST.collectIssues(checks, value, undefined, ast, options)
            if (issues) {
              return Effect.fail(new SchemaIssue.Composite(ast, issues, value, options))
            }
          }
          return Effect.succeed(value)
        })
      }
    }

    return result
  }
  const parseLocal = specialize === undefined ? parseChecks : specialize(parseChecks)
  if (!links) {
    return parseLocal
  }
  return (
    input: unknown,
    options: SchemaAST.ParseOptions
  ) => {
    const parsers = encodingParsers ??= links.map((link) => compile(link.to))
    let current = input
    let result = parsers[parsers.length - 1](input, options)
    for (let i = links.length - 1; i >= 0; i--) {
      result = transformations![i](result, current, options)
      if (i !== 0) {
        const next = parsers[i - 1]
        if ((result as Exit.Exit<unknown, unknown>)._tag === "Success") {
          current = (result as InternalParser.Success<unknown, SchemaIssue.Issue>)[InternalParser.args]
          result = next(current, options)
        } else {
          result = Effect.flatMapEager(result, (value) => {
            const nextResult = next(value, options)
            return nextResult === InternalParser.sameExit ? InternalParser.succeed(value) : nextResult
          })
        }
      }
    }
    if ((result as Exit.Exit<unknown, unknown>)._tag === "Success") {
      const value = (result as InternalParser.Success<unknown, SchemaIssue.Issue>)[InternalParser.args]
      const local = parseLocal(value, options)
      return local === InternalParser.sameExit ? result : local
    }
    result = wrapEncoding(ast, input, options, result)
    return Effect.flatMapEager(result, (value) => {
      const local = parseLocal(value, options)
      return local === InternalParser.sameExit ? InternalParser.succeed(value) : local
    })
  }
}