use std::path::Path;

use serde::{Deserialize, Serialize};

/// Quote a string field for CSV output: wrap in double-quotes and escape
/// internal double-quotes by doubling them (RFC 4180).
fn csv_quote(s: &str) -> String {
  if s.contains([',', '"', '\n', '\r']) {
    format!("\"{}\"", s.replace('"', "\"\""))
  } else {
    s.to_string()
  }
}

use crate::{error::Result, jobs::ExportFormat, storage::DynStorageBackend};

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ExportResult {
  pub items_exported: usize,
  pub output_path:    String,
}

/// Export library data to the specified format.
///
/// # Errors
///
/// Returns an error if the storage query fails or if the output file cannot
/// be written.
pub async fn export_library(
  storage: &DynStorageBackend,
  format: &ExportFormat,
  destination: &Path,
) -> Result<ExportResult> {
  let pagination = crate::model::Pagination {
    offset: 0,
    limit:  u64::MAX,
    sort:   None,
  };
  let items = storage.list_media(&pagination).await?;
  let count = items.len();

  match format {
    ExportFormat::Json => {
      let json = serde_json::to_string_pretty(&items).map_err(|e| {
        crate::error::PinakesError::Serialization(format!(
          "json serialize: {e}"
        ))
      })?;
      std::fs::write(destination, json)?;
    },
    ExportFormat::Csv => {
      let mut csv = String::new();
      csv.push_str(
        "id,path,file_name,media_type,content_hash,file_size,title,artist,\
         album,genre,year,duration_secs,description,created_at,updated_at\n",
      );
      for item in &items {
        use std::fmt::Write as _;
        writeln!(
          csv,
          "{},{},{},{},{},{},{},{},{},{},{},{},{},{},{}",
          item.id,
          csv_quote(&item.path.display().to_string()),
          csv_quote(&item.file_name),
          csv_quote(&format!("{:?}", item.media_type)),
          item.content_hash,
          item.file_size,
          csv_quote(item.title.as_deref().unwrap_or("")),
          csv_quote(item.artist.as_deref().unwrap_or("")),
          csv_quote(item.album.as_deref().unwrap_or("")),
          csv_quote(item.genre.as_deref().unwrap_or("")),
          item.year.map(|y| y.to_string()).unwrap_or_default(),
          item
            .duration_secs
            .map(|d| d.to_string())
            .unwrap_or_default(),
          csv_quote(item.description.as_deref().unwrap_or("")),
          item.created_at,
          item.updated_at,
        )
        .unwrap_or_default();
      }
      std::fs::write(destination, csv)?;
    },
  }

  Ok(ExportResult {
    items_exported: count,
    output_path:    destination.to_string_lossy().to_string(),
  })
}