use crate::format;
use crate::map::Map;
use crate::value::{Value, ValueKind};
use std::error::Error;
use std::fmt;
use std::mem;
use yaml_rust as yaml;

pub fn parse(
  uri: Option<&String>,
  text: &str,
) -> Result<Map<String, Value>, Box<dyn Error + Send + Sync>> {
  // Parse a YAML object from file
  let mut docs = yaml::YamlLoader::load_from_str(text)?;
  let root = match docs.len() {
    0 => yaml::Yaml::Hash(yaml::yaml::Hash::new()),
    1 => mem::replace(&mut docs[0], yaml::Yaml::Null),
    n => {
      return Err(Box::new(MultipleDocumentsError(n)));
    }
  };

  let value = from_yaml_value(uri, &root)?;
  format::extract_root_table(uri, value)
}

fn from_yaml_value(
  uri: Option<&String>,
  value: &yaml::Yaml,
) -> Result<Value, Box<dyn Error + Send + Sync>> {
  match *value {
    yaml::Yaml::String(ref value) => Ok(Value::new(uri, ValueKind::String(value.clone()))),
    yaml::Yaml::Real(ref value) => {
      // TODO: Figure out in what cases this can panic?
      value
        .parse::<f64>()
        .map_err(|_| {
          Box::new(FloatParsingError(value.to_string())) as Box<(dyn Error + Send + Sync)>
        })
        .map(ValueKind::Float)
        .map(|f| Value::new(uri, f))
    }
    yaml::Yaml::Integer(value) => Ok(Value::new(uri, ValueKind::I64(value))),
    yaml::Yaml::Boolean(value) => Ok(Value::new(uri, ValueKind::Boolean(value))),
    yaml::Yaml::Hash(ref table) => {
      let mut m = Map::new();
      for (key, value) in table {
        match key {
          yaml::Yaml::String(k) => m.insert(k.to_owned(), from_yaml_value(uri, value)?),
          yaml::Yaml::Integer(k) => m.insert(k.to_string(), from_yaml_value(uri, value)?),
          _ => unreachable!(),
        };
      }
      Ok(Value::new(uri, ValueKind::Table(m)))
    }
    yaml::Yaml::Array(ref array) => {
      let mut l = Vec::new();

      for value in array {
        l.push(from_yaml_value(uri, value)?);
      }

      Ok(Value::new(uri, ValueKind::Array(l)))
    }

    // 1. Yaml NULL
    // 2. BadValue – It shouldn't be possible to hit BadValue as this only happens when
    //               using the index trait badly or on a type error but we send back nil.
    // 3. Alias – No idea what to do with this and there is a note in the lib that its
    //            not fully supported yet anyway
    _ => Ok(Value::new(uri, ValueKind::Nil)),
  }
}

#[derive(Debug, Copy, Clone)]
struct MultipleDocumentsError(usize);

impl fmt::Display for MultipleDocumentsError {
  fn fmt(&self, format: &mut fmt::Formatter) -> fmt::Result {
    write!(format, "Got {} YAML documents, expected 1", self.0)
  }
}

impl Error for MultipleDocumentsError {
  fn description(&self) -> &str {
    "More than one YAML document provided"
  }
}

#[derive(Debug, Clone)]
struct FloatParsingError(String);

impl fmt::Display for FloatParsingError {
  fn fmt(&self, format: &mut fmt::Formatter) -> fmt::Result {
    write!(format, "Parsing {} as floating point number failed", self.0)
  }
}

impl Error for FloatParsingError {
  fn description(&self) -> &str {
    "Floating point number parsing failed"
  }
}
