import gleam/dict
import gleam/float
import gleam/int
import gleam/list
import gleam/option.{None, Some}
import gleam/result
import gleam/string
import gleam/uri
import qs

pub type OneOrMany {
  One(String)
  Many(List(String))
}

fn map_one_or_many(
  one_or_many: OneOrMany,
  mapper: fn(String) -> String,
) -> OneOrMany {
  case one_or_many {
    One(value) -> One(mapper(value))
    Many(values) -> Many(list.map(values, mapper))
  }
}

pub type QueryAdv =
  qs.Query(OneOrMany)

pub type Scheme {
  SchemeListAsMultipleValues(list_suffix: String)
  SchemeListAsSingleValue(list_suffix: String, separator: String)
}

pub fn scheme_rails_like() -> Scheme {
  SchemeListAsMultipleValues(list_suffix: "[]")
}

pub type Config {
  Config(fail_on_invalid: Bool, scheme: Scheme)
}

pub fn default_config() -> Config {
  Config(fail_on_invalid: False, scheme: scheme_rails_like())
}

pub fn with_scheme(config: Config, scheme: Scheme) -> Config {
  Config(..config, scheme: scheme)
}

/// Parse a query string
///
/// ## Example
///
/// ```
/// "?color=red&tags[]=large&tags[]=wool"
/// |> qs.default_parse
///
/// ==
///
/// Ok(
///   dict.from_list(
///     [ #("color", One("red")), #("tags", Many(["large", "wool"])) ]
///   )
/// )
/// ```
///
pub fn default_parse(qs: String) -> Result(QueryAdv, String) {
  parse(qs, default_config())
}

pub fn parse(input: String, config: Config) -> Result(QueryAdv, String) {
  use key_values <- result.then(qs.split_and_parse(
    input,
    config.fail_on_invalid,
  ))

  list.fold(over: key_values, from: empty(), with: fn(query, key_value) {
    add_key_value(config.scheme, query, key_value)
  })
  |> Ok
}

fn add_key_value(
  scheme: Scheme,
  query: QueryAdv,
  key_value: qs.RawKeyValue,
) -> QueryAdv {
  let #(raw_key, raw_value) = key_value

  let list_suffix = scheme.list_suffix
  let key_without_suffix = string.replace(raw_key, list_suffix, "")
  let is_list = raw_key != key_without_suffix

  let updater = fn(res) {
    case is_list, res {
      True, Some(existing) -> {
        case existing {
          One(_) -> value_as_many(raw_value, [], scheme)
          Many(existing_values) ->
            value_as_many(raw_value, existing_values, scheme)
        }
      }
      // The list doesn't exist yet
      True, None -> value_as_many(raw_value, [], scheme)
      // A single value is always replaced
      // So we don't care if it exists
      False, _ -> One(raw_value)
    }
  }

  dict.upsert(in: query, update: key_without_suffix, with: updater)
}

fn value_as_many(
  raw_value: String,
  existing_values: List(String),
  scheme: Scheme,
) -> OneOrMany {
  let added_values = get_list_value(raw_value, scheme)
  let next_values = list.append(existing_values, added_values)
  Many(next_values)
}

fn get_list_value(raw_value: String, scheme: Scheme) -> List(String) {
  case scheme {
    SchemeListAsSingleValue(_, separator) -> {
      string.split(raw_value, separator)
    }
    SchemeListAsMultipleValues(_) -> [raw_value]
  }
}

/// Serialize a query
///
/// ## Example
///
/// ```
/// [ #("color", One("red")), #("tags", Many(["large", "wool"])) ]
/// |> qs.serialize
///
/// ==
///
/// "?color=red&tags[]=large&tags[]=wool"
/// ```
pub fn default_serialize(query: QueryAdv) -> String {
  serialize(query, default_config())
}

pub fn serialize(input: QueryAdv, config: Config) -> String {
  input
  |> dict.to_list
  |> list.map(encode_key_and_values)
  |> list.map(add_key_suffix(_, config.scheme))
  |> list.flat_map(unfold_values(_, config.scheme))
  |> list.map(join_key_value)
  |> string.join("&")
  |> qs.add_question_mark
}

fn encode_key_and_values(key_value: #(String, OneOrMany)) {
  let #(key, one_or_many) = key_value
  #(qs.encode(key), map_one_or_many(one_or_many, qs.encode))
}

fn add_key_suffix(
  key_value: #(String, OneOrMany),
  scheme: Scheme,
) -> #(String, OneOrMany) {
  let #(key, one_or_many) = key_value

  case one_or_many {
    One(_) -> key_value
    Many(values) -> {
      #(add_list_suffix_or_key(key, scheme), Many(values))
    }
  }
}

fn add_list_suffix_or_key(key: String, scheme: Scheme) -> String {
  key <> scheme.list_suffix
}

fn unfold_values(
  key_value: #(String, OneOrMany),
  scheme: Scheme,
) -> List(qs.RawKeyValue) {
  let #(key, one_or_many) = key_value

  case one_or_many {
    One(value) -> [#(key, value)]
    Many(values) -> unfold_key_value_many(key, values, scheme)
  }
}

fn unfold_key_value_many(
  key: String,
  values: List(String),
  scheme: Scheme,
) -> List(qs.RawKeyValue) {
  case scheme {
    SchemeListAsSingleValue(_, separator) -> {
      [#(key, string.join(values, separator))]
    }
    SchemeListAsMultipleValues(_) -> {
      list.map(values, fn(value) { #(key, value) })
    }
  }
}

fn join_key_value(tuple) {
  let #(key, value) = tuple
  key <> "=" <> value
}

// fn encode_reserved(input: String) -> String {
//   list.fold(over: reserved_chars, from: input, with: fn(input, char) {
//     string.replace(input, char, encode(char))
//   })
// }

// fn encode(val) {
//   uri.percent_encode(val)
// }

pub fn empty() -> QueryAdv {
  qs.empty()
}

pub fn get(query: QueryAdv, key: String) -> Result(OneOrMany, String) {
  qs.get(query, key)
}

/// Attempt to get one value as a String.
/// If the value is a list this fails.
pub fn get_as_string(query: QueryAdv, key: String) -> Result(String, String) {
  use one_or_many <- result.then(get(query, key))

  case one_or_many {
    One(value) -> Ok(value)
    Many(_) ->
      Error(
        key
        |> string.append(" is a list"),
      )
  }
}

/// Attempt to get one value as a Bool.
/// If the value is a list this fails.
/// If the value cannot be parsed to a Bool this fails.
pub fn get_as_bool(query: QueryAdv, key: String) -> Result(Bool, String) {
  get_as_string(query, key)
  |> result.then(parse_bool)
}

/// Attempt to get one value as an Int.
/// If the value is a list this fails.
/// If the value cannot be parsed to an Int this fails.
pub fn get_as_int(query: QueryAdv, key: String) -> Result(Int, String) {
  use value <- result.then(get_as_string(query, key))

  value
  |> int.parse
  |> result.replace_error(
    "Invalid Int "
    |> string.append(value),
  )
}

/// Attempt to get one value as an Float.
/// If the value is a list this fail.
pub fn get_as_float(query: QueryAdv, key: String) -> Result(Float, String) {
  use value <- result.then(get_as_string(query, key))

  value
  |> float.parse
  |> result.replace_error(
    "Invalid Float "
    |> string.append(value),
  )
}

/// Get values from the query as a list of strings (regardless if one or many).
/// If key is not present this defaults to an empty list.
pub fn get_as_list(query: QueryAdv, key: String) -> List(String) {
  maybe_get_as_list(query, key)
  |> result.unwrap([])
}

/// Attempt to get values as a list of Bool.
pub fn get_as_list_of_bool(
  query: QueryAdv,
  key: String,
) -> Result(List(Bool), String) {
  get_as_list(query, key)
  |> list.map(parse_bool)
  |> result.all
}

/// Attempt to get values as a list of Int.
pub fn get_as_list_of_int(
  query: QueryAdv,
  key: String,
) -> Result(List(Int), String) {
  get_as_list(query, key)
  |> list.map(int.parse)
  |> result.all
  |> result.replace_error("Couldn't parse all values")
}

/// Attempt to get values as a list of Float.
pub fn get_as_list_of_float(
  query: QueryAdv,
  key: String,
) -> Result(List(Float), String) {
  get_as_list(query, key)
  |> list.map(float.parse)
  |> result.all
  |> result.replace_error("Couldn't parse all values")
}

/// Get values from the query as a list of strings.
/// If key is not present this returns an Error.
pub fn maybe_get_as_list(
  query: QueryAdv,
  key: String,
) -> Result(List(String), String) {
  get(query, key)
  |> result.map(to_list)
}

/// Tell if the query has the given key.
pub fn has_key(query: QueryAdv, key: String) -> Bool {
  qs.has_key(query, key)
}

/// Insert value.
pub fn insert(query: QueryAdv, key: String, value: OneOrMany) {
  qs.insert(query, key, value)
}

/// Set a unique value in the query.
pub fn insert_one(query: QueryAdv, key: String, value: String) {
  insert(query, key, One(value))
}

/// Set a list of values in the query.
pub fn insert_list(query: QueryAdv, key: String, values: List(String)) {
  insert(query, key, Many(values))
}

pub fn merge(a: QueryAdv, b: QueryAdv) {
  qs.merge(a, b)
}

pub fn delete(query: QueryAdv, key: String) {
  qs.delete(query, key)
}

fn to_list(one_or_many: OneOrMany) -> List(String) {
  case one_or_many {
    One(value) -> [value]
    Many(values) -> values
  }
}

fn parse_bool(s: String) -> Result(Bool, String) {
  case s {
    "true" -> Ok(True)
    "false" -> Ok(False)
    _ ->
      Error(
        "Invalid "
        |> string.append(s),
      )
  }
}