use anyhow::{Result, anyhow};
use serde::{Deserialize, Serialize};

/// Código de idioma ISO 639-2 (3 letras minúsculas), ex: "por", "eng".
#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct TrackLanguage(String);

impl TrackLanguage {
    /// Cria um TrackLanguage validando o formato ISO 639-2 (3 letras minúsculas).
    pub fn new(code: impl Into<String>) -> Result<Self> {
        let code = code.into();
        if code.len() == 3 && code.chars().all(|c| c.is_ascii_lowercase()) {
            Ok(TrackLanguage(code))
        } else {
            Err(anyhow!(
                "Código de idioma inválido: '{}'. Esperado formato ISO 639-2 (3 letras minúsculas, ex: 'por', 'eng')",
                code
            ))
        }
    }

    pub fn as_str(&self) -> &str {
        &self.0
    }
}

impl std::fmt::Display for TrackLanguage {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn idioma_valido() {
        assert!(TrackLanguage::new("por").is_ok());
        assert!(TrackLanguage::new("eng").is_ok());
    }

    #[test]
    fn idioma_invalido_curto() {
        assert!(TrackLanguage::new("pt").is_err());
    }

    #[test]
    fn idioma_invalido_maiusculo() {
        assert!(TrackLanguage::new("POR").is_err());
    }

    #[test]
    fn idioma_invalido_longo() {
        assert!(TrackLanguage::new("port").is_err());
    }
}