import gleam/dynamic
import gleam/json
import gleam/string
import json_serde
import query_error.{type QueryError, QueryError}
import tree
import tree_events

/// Parses a string query into corresponding TreeEvent
/// 
/// Query formats:
/// 
/// - get (path)
/// - set (path) (data)
pub fn parse(query: String) {
  let args = query |> string.split(" ")
  case args {
    ["get", path] -> {
      case path |> parse_path {
        Error(_) -> Error(QueryError("Wrong query format."))
        Ok(#(head, tail)) ->
          #(head, fn(actor) { tree_events.GetEvent(tail, actor) })
          |> Ok
      }
    }
    ["set", path, data] -> {
      case path |> parse_path {
        Error(_) -> Error(QueryError("Wrong query format."))
        Ok(#(head, tail)) -> {
          let assert Ok(data) = data |> json.decode(dynamic.dynamic)
          let data = data |> json_serde.decode_leafdata
          case data {
            Error(_) -> Error(QueryError("Wrong data format."))
            Ok(data) ->
              #(head, fn(actor) { tree_events.SetEvent(tail, data, actor) })
              |> Ok
          }
        }
      }
    }
    _ -> Error(QueryError("Wrong query format."))
  }
}

pub fn get(tree, path) -> Result(tree.Tree, QueryError) {
  let res = tree.get(tree, path)
  case res {
    Error(_) -> Error(QueryError("There is no such node."))
    Ok(tree) -> Ok(tree)
  }
}

pub fn set(tree, path, data) -> Result(tree.Tree, QueryError) {
  Ok(tree.set(tree, path, data))
}

pub fn parse_path(path) {
  case path |> string.split(".") {
    [head, ..tail] -> Ok(#(head, tail))
    _ -> Error(QueryError("Bad path."))
  }
}