/**
 * Search param validation for One routes.
 *
 * Provides type-safe search param parsing and validation with support for
 * Zod, Valibot, and custom validation functions.
 */

/**
 * Standard Schema interface (from standard-schema.dev)
 * Used by Valibot, ArkType, and others for interop.
 */
export interface StandardSchema<Input = unknown, Output = unknown> {
  readonly '~standard': {
    readonly version: 1
    readonly vendor: string
    readonly validate: (
      value: unknown
    ) =>
      | { readonly value: Output; readonly issues?: undefined }
      | { readonly value?: undefined; readonly issues: readonly unknown[] }
  }
}

/**
 * Zod-like schema interface
 */
export interface ZodLikeSchema<Output = unknown> {
  parse(value: unknown): Output
  safeParse?(
    value: unknown
  ): { success: true; data: Output } | { success: false; error: unknown }
}

/**
 * Custom validator function type
 */
export type SearchValidatorFn<TInput, TOutput> = (input: TInput) => TOutput

/**
 * All supported validator types
 */
export type SearchValidator<TInput = Record<string, unknown>, TOutput = TInput> =
  | StandardSchema<TInput, TOutput>
  | ZodLikeSchema<TOutput>
  | SearchValidatorFn<TInput, TOutput>

/**
 * Infer the output type from a validator
 */
export type InferSearchOutput<T> =
  T extends StandardSchema<any, infer O>
    ? O
    : T extends ZodLikeSchema<infer O>
      ? O
      : T extends SearchValidatorFn<any, infer O>
        ? O
        : never

/**
 * Infer the input type from a validator
 */
export type InferSearchInput<T> =
  T extends StandardSchema<infer I, any>
    ? I
    : T extends ZodLikeSchema<any>
      ? Record<string, unknown>
      : T extends SearchValidatorFn<infer I, any>
        ? I
        : never

/**
 * Error thrown when search param validation fails
 */
export class SearchValidationError extends Error {
  readonly routerCode = 'VALIDATE_SEARCH'
  readonly issues: unknown[]

  constructor(message: string, issues: unknown[] = []) {
    super(message)
    this.name = 'SearchValidationError'
    this.issues = issues
  }
}

/**
 * Check if a value is a Standard Schema
 */
function isStandardSchema(value: unknown): value is StandardSchema {
  return (
    typeof value === 'object' &&
    value !== null &&
    '~standard' in value &&
    typeof (value as any)['~standard']?.validate === 'function'
  )
}

/**
 * Check if a value is a Zod-like schema
 */
function isZodLikeSchema(value: unknown): value is ZodLikeSchema {
  return (
    typeof value === 'object' &&
    value !== null &&
    typeof (value as any).parse === 'function'
  )
}

/**
 * Check if a value is a validator function
 */
function isValidatorFn(value: unknown): value is SearchValidatorFn<unknown, unknown> {
  return typeof value === 'function'
}

/**
 * Parse search params from URL search string
 */
export function parseSearchString(search: string): Record<string, string | string[]> {
  const params: Record<string, string | string[]> = {}
  const searchParams = new URLSearchParams(search)

  searchParams.forEach((value, key) => {
    const existing = params[key]
    if (existing === undefined) {
      params[key] = value
    } else if (Array.isArray(existing)) {
      existing.push(value)
    } else {
      params[key] = [existing, value]
    }
  })

  return params
}

/**
 * Validate search params using the provided validator
 *
 * @param validator - The validator to use (Standard Schema, Zod-like, or function)
 * @param input - The raw search params to validate
 * @returns The validated and transformed search params
 * @throws SearchValidationError if validation fails
 */
export function validateSearch<T extends SearchValidator>(
  validator: T,
  input: Record<string, unknown>
): InferSearchOutput<T> {
  if (isStandardSchema(validator)) {
    const result = validator['~standard'].validate(input)
    if (result.issues) {
      throw new SearchValidationError(
        'Search param validation failed',
        result.issues as unknown[]
      )
    }
    return result.value as InferSearchOutput<T>
  }

  if (isZodLikeSchema(validator)) {
    if (validator.safeParse) {
      const result = validator.safeParse(input)
      if (!result.success) {
        throw new SearchValidationError('Search param validation failed', [result.error])
      }
      return result.data as InferSearchOutput<T>
    }
    // Fallback to parse which throws on error
    try {
      return validator.parse(input) as InferSearchOutput<T>
    } catch (error) {
      throw new SearchValidationError('Search param validation failed', [error])
    }
  }

  if (isValidatorFn(validator)) {
    try {
      return validator(input) as InferSearchOutput<T>
    } catch (error) {
      throw new SearchValidationError('Search param validation failed', [error])
    }
  }

  throw new Error('Invalid validator provided to validateSearch')
}

/**
 * Create a search param validator from a Zod schema.
 * This adapter wraps Zod schemas for use with One's validateSearch.
 *
 * @example
 * ```ts
 * import { z } from 'zod'
 * import { zodSearchValidator } from 'one'
 *
 * const searchSchema = z.object({
 *   page: z.number().default(1),
 *   filter: z.string().optional(),
 * })
 *
 * export const validateSearch = zodSearchValidator(searchSchema)
 * ```
 */
export function zodSearchValidator<T extends ZodLikeSchema>(schema: T): T {
  return schema
}

/**
 * Create a fallback wrapper for search param fields.
 * Returns the fallback value if parsing fails instead of throwing.
 *
 * @example
 * ```ts
 * import { z } from 'zod'
 * import { withFallback } from 'one'
 *
 * const schema = z.object({
 *   page: withFallback(z.number(), 1),
 * })
 * ```
 */
export function withFallback<T>(
  schema: ZodLikeSchema<T>,
  fallbackValue: T
): ZodLikeSchema<T> {
  return {
    parse(value: unknown): T {
      try {
        return schema.parse(value)
      } catch {
        return fallbackValue
      }
    },
    safeParse(value: unknown) {
      try {
        return { success: true as const, data: schema.parse(value) }
      } catch {
        return { success: true as const, data: fallbackValue }
      }
    },
  }
}