use std::fmt::Write as _;

use serde::{Deserialize, Serialize};

use crate::error::{PinakesError, Result};

/// `OpenLibrary` API client for book metadata enrichment
pub struct OpenLibraryClient {
  client:   reqwest::Client,
  base_url: String,
}

impl Default for OpenLibraryClient {
  fn default() -> Self {
    Self::new()
  }
}

impl OpenLibraryClient {
  /// Create a new `OpenLibraryClient`.
  #[must_use]
  pub fn new() -> Self {
    let client = reqwest::Client::builder()
      .user_agent("Pinakes/1.0")
      .timeout(std::time::Duration::from_secs(10))
      .build()
      .unwrap_or_else(|_| reqwest::Client::new());
    Self {
      client,
      base_url: "https://openlibrary.org".to_string(),
    }
  }

  /// Fetch book metadata by ISBN
  ///
  /// # Errors
  ///
  /// Returns an error if the HTTP request fails or the response cannot be
  /// parsed.
  pub async fn fetch_by_isbn(&self, isbn: &str) -> Result<OpenLibraryBook> {
    let url = format!("{}/isbn/{}.json", self.base_url, isbn);

    let response = self.client.get(&url).send().await.map_err(|e| {
      PinakesError::External(format!("OpenLibrary request failed: {e}"))
    })?;

    if !response.status().is_success() {
      return Err(PinakesError::External(format!(
        "OpenLibrary returned status: {}",
        response.status()
      )));
    }

    response.json::<OpenLibraryBook>().await.map_err(|e| {
      PinakesError::External(format!(
        "Failed to parse OpenLibrary response: {e}"
      ))
    })
  }

  /// Search for books by title and author
  ///
  /// # Errors
  ///
  /// Returns an error if the HTTP request fails or the response cannot be
  /// parsed.
  pub async fn search(
    &self,
    title: &str,
    author: Option<&str>,
  ) -> Result<Vec<OpenLibrarySearchResult>> {
    let mut url = format!(
      "{}/search.json?title={}",
      self.base_url,
      urlencoding::encode(title)
    );

    if let Some(author) = author {
      let _ = write!(url, "&author={}", urlencoding::encode(author));
    }

    url.push_str("&limit=5");

    let response = self.client.get(&url).send().await.map_err(|e| {
      PinakesError::External(format!("OpenLibrary search failed: {e}"))
    })?;

    if !response.status().is_success() {
      return Err(PinakesError::External(format!(
        "OpenLibrary search returned status: {}",
        response.status()
      )));
    }

    let search_response: OpenLibrarySearchResponse =
      response.json().await.map_err(|e| {
        PinakesError::External(format!("Failed to parse search results: {e}"))
      })?;

    Ok(search_response.docs)
  }

  /// Fetch cover image by cover ID
  ///
  /// # Errors
  ///
  /// Returns an error if the HTTP request fails or the response cannot be
  /// read.
  pub async fn fetch_cover(
    &self,
    cover_id: i64,
    size: CoverSize,
  ) -> Result<Vec<u8>> {
    let size_str = match size {
      CoverSize::Small => "S",
      CoverSize::Medium => "M",
      CoverSize::Large => "L",
    };

    let url =
      format!("https://covers.openlibrary.org/b/id/{cover_id}-{size_str}.jpg");

    let response = self.client.get(&url).send().await.map_err(|e| {
      PinakesError::External(format!("Cover download failed: {e}"))
    })?;

    if !response.status().is_success() {
      return Err(PinakesError::External(format!(
        "Cover download returned status: {}",
        response.status()
      )));
    }

    response.bytes().await.map(|b| b.to_vec()).map_err(|e| {
      PinakesError::External(format!("Failed to read cover data: {e}"))
    })
  }

  /// Fetch cover by ISBN
  ///
  /// # Errors
  ///
  /// Returns an error if the HTTP request fails or the response cannot be
  /// read.
  pub async fn fetch_cover_by_isbn(
    &self,
    isbn: &str,
    size: CoverSize,
  ) -> Result<Vec<u8>> {
    let size_str = match size {
      CoverSize::Small => "S",
      CoverSize::Medium => "M",
      CoverSize::Large => "L",
    };

    let url =
      format!("https://covers.openlibrary.org/b/isbn/{isbn}-{size_str}.jpg");

    let response = self.client.get(&url).send().await.map_err(|e| {
      PinakesError::External(format!("Cover download failed: {e}"))
    })?;

    if !response.status().is_success() {
      return Err(PinakesError::External(format!(
        "Cover download returned status: {}",
        response.status()
      )));
    }

    response.bytes().await.map(|b| b.to_vec()).map_err(|e| {
      PinakesError::External(format!("Failed to read cover data: {e}"))
    })
  }
}

#[derive(Debug, Clone, Copy)]
pub enum CoverSize {
  Small,  // 256x256
  Medium, // 600x800
  Large,  // Original
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct OpenLibraryBook {
  #[serde(default)]
  pub title: Option<String>,

  #[serde(default)]
  pub subtitle: Option<String>,

  #[serde(default)]
  pub authors: Vec<AuthorRef>,

  #[serde(default)]
  pub publishers: Vec<String>,

  #[serde(default)]
  pub publish_date: Option<String>,

  #[serde(default)]
  pub number_of_pages: Option<i32>,

  #[serde(default)]
  pub subjects: Vec<String>,

  #[serde(default)]
  pub covers: Vec<i64>,

  #[serde(default)]
  pub isbn_10: Vec<String>,

  #[serde(default)]
  pub isbn_13: Vec<String>,

  #[serde(default)]
  pub series: Vec<String>,

  #[serde(default)]
  pub description: Option<StringOrObject>,

  #[serde(default)]
  pub languages: Vec<LanguageRef>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AuthorRef {
  pub key: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LanguageRef {
  pub key: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(untagged)]
pub enum StringOrObject {
  String(String),
  Object { value: String },
}

impl StringOrObject {
  #[must_use]
  pub fn as_str(&self) -> &str {
    match self {
      Self::String(s) => s,
      Self::Object { value } => value,
    }
  }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct OpenLibrarySearchResponse {
  #[serde(default)]
  pub docs: Vec<OpenLibrarySearchResult>,

  #[serde(default)]
  pub num_found: i32,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct OpenLibrarySearchResult {
  #[serde(default)]
  pub key: Option<String>,

  #[serde(default)]
  pub title: Option<String>,

  #[serde(default)]
  pub author_name: Vec<String>,

  #[serde(default)]
  pub first_publish_year: Option<i32>,

  #[serde(default)]
  pub publisher: Vec<String>,

  #[serde(default)]
  pub isbn: Vec<String>,

  #[serde(default)]
  pub cover_i: Option<i64>,

  #[serde(default)]
  pub subject: Vec<String>,
}

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

  #[tokio::test]
  async fn test_openlibrary_client_creation() {
    let client = OpenLibraryClient::new();
    assert_eq!(client.base_url, "https://openlibrary.org");
  }

  #[test]
  fn test_string_or_object_parsing() {
    let string_desc: StringOrObject =
      serde_json::from_str(r#""Simple description""#).unwrap();
    assert_eq!(string_desc.as_str(), "Simple description");

    let object_desc: StringOrObject =
      serde_json::from_str(r#"{"value": "Object description"}"#).unwrap();
    assert_eq!(object_desc.as_str(), "Object description");
  }
}