// List state lives in the URL query (design: Interactions, D-22): search,
// sort, dir, page, per_page and filter[<name>]. These helpers convert between
// the route query and the typed list query the API client sends. Anything
// malformed (a non-numeric page, an unknown direction, an empty filter) is
// dropped, so a hand-edited URL never reaches the server half-valid.
import type { LocationQuery, LocationQueryRaw } from 'vue-router'
import type { ListQuery } from '../api/types'

/** A list row's id as the record carries it. */
export type RowId = number | string

const FILTER_KEY = /^filter\[(.+)\]$/
const POSITIVE = /^[1-9]\d*$/

function first(value: LocationQuery[string] | undefined): string {
  const raw = Array.isArray(value) ? value[value.length - 1] : value
  return typeof raw === 'string' ? raw : ''
}

function positive(value: string): number | undefined {
  return POSITIVE.test(value) ? Number(value) : undefined
}

export function parseListQuery(query: LocationQuery): ListQuery {
  const out: ListQuery = {}
  const search = first(query.search).trim()
  if (search !== '') {
    out.search = search
  }
  const sort = first(query.sort).trim()
  if (sort !== '') {
    out.sort = sort
    const dir = first(query.dir)
    out.dir = dir === 'desc' ? 'desc' : 'asc'
  }
  const page = positive(first(query.page))
  if (page !== undefined) {
    out.page = page
  }
  const perPage = positive(first(query.per_page))
  if (perPage !== undefined) {
    out.per_page = perPage
  }
  const filter: Record<string, string> = {}
  for (const key of Object.keys(query).sort()) {
    const name = FILTER_KEY.exec(key)?.[1]
    const value = first(query[key])
    if (name && value !== '') {
      filter[name] = value
    }
  }
  if (Object.keys(filter).length > 0) {
    out.filter = filter
  }
  return out
}

export function toListQuery(input: ListQuery): LocationQueryRaw {
  const out: LocationQueryRaw = {}
  if (input.search) {
    out.search = input.search
  }
  if (input.sort) {
    out.sort = input.sort
    out.dir = input.dir === 'desc' ? 'desc' : 'asc'
  }
  if (input.page !== undefined && input.page > 1) {
    out.page = String(input.page)
  }
  if (input.per_page !== undefined) {
    out.per_page = String(input.per_page)
  }
  for (const name of Object.keys(input.filter ?? {}).sort()) {
    const value = input.filter?.[name]
    if (value !== undefined && value !== '') {
      out[`filter[${name}]`] = value
    }
  }
  return out
}

/** A stable key for comparing two list queries. */
export function listQueryKey(input: ListQuery): string {
  return JSON.stringify(toListQuery(input))
}