use std::{
  env,
  fmt,
  fs,
  io::{BufRead, BufReader, Read, Write},
  str,
};

use base64::{Engine, engine::general_purpose::STANDARD};
use imagesize::{ImageSize, ImageType};
use log::{error, info, warn};
use regex::Regex;
use rusqlite::{Connection, OptionalExtension, params};
use serde::{Deserialize, Serialize};
use serde_json::json;
use thiserror::Error;

#[derive(Error, Debug)]
pub enum StashError {
  #[error("Input is empty or too large, skipping store.")]
  EmptyOrTooLarge,
  #[error("Input is all whitespace, skipping store.")]
  AllWhitespace,

  #[error("Failed to store entry: {0}")]
  Store(String),
  #[error("Error reading entry during deduplication: {0}")]
  DeduplicationRead(String),
  #[error("Error decoding entry during deduplication: {0}")]
  DeduplicationDecode(String),
  #[error("Failed to remove entry during deduplication: {0}")]
  DeduplicationRemove(String),
  #[error("Failed to trim entry: {0}")]
  Trim(String),
  #[error("No entries to delete")]
  NoEntriesToDelete,
  #[error("Failed to delete last entry: {0}")]
  DeleteLast(String),
  #[error("Failed to wipe database: {0}")]
  Wipe(String),
  #[error("Failed to decode entry during list: {0}")]
  ListDecode(String),
  #[error("Failed to read input for decode: {0}")]
  DecodeRead(String),
  #[error("Failed to extract id for decode: {0}")]
  DecodeExtractId(String),
  #[error("Failed to get entry for decode: {0}")]
  DecodeGet(String),

  #[error("Failed to write decoded entry: {0}")]
  DecodeWrite(String),
  #[error("Failed to delete entry during query delete: {0}")]
  QueryDelete(String),
  #[error("Failed to delete entry with id {0}: {1}")]
  DeleteEntry(u64, String),
}

pub trait ClipboardDb {
  fn store_entry(
    &self,
    input: impl Read,
    max_dedupe_search: u64,
    max_items: u64,
  ) -> Result<u64, StashError>;
  fn deduplicate(&self, buf: &[u8], max: u64) -> Result<usize, StashError>;
  fn trim_db(&self, max: u64) -> Result<(), StashError>;
  fn delete_last(&self) -> Result<(), StashError>;
  fn wipe_db(&self) -> Result<(), StashError>;
  fn list_entries(
    &self,
    out: impl Write,
    preview_width: u32,
  ) -> Result<usize, StashError>;
  fn decode_entry(
    &self,
    in_: impl Read,
    out: impl Write,
    input: Option<String>,
  ) -> Result<(), StashError>;
  fn delete_query(&self, query: &str) -> Result<usize, StashError>;
  fn delete_entries(&self, in_: impl Read) -> Result<usize, StashError>;
  fn next_sequence(&self) -> u64;
}

#[derive(Serialize, Deserialize)]
pub struct Entry {
  pub contents: Vec<u8>,
  pub mime:     Option<String>,
}

impl fmt::Display for Entry {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    let preview = preview_entry(&self.contents, self.mime.as_deref(), 100);
    write!(f, "{preview}")
  }
}

pub struct SqliteClipboardDb {
  pub conn: Connection,
}

impl SqliteClipboardDb {
  pub fn new(conn: Connection) -> Result<Self, StashError> {
    conn
      .execute_batch(
        "CREATE TABLE IF NOT EXISTS clipboard (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                contents BLOB NOT NULL,
                mime TEXT
            );",
      )
      .map_err(|e| StashError::Store(e.to_string()))?;
    Ok(Self { conn })
  }
}

impl SqliteClipboardDb {
  pub fn list_json(&self) -> Result<String, StashError> {
    let mut stmt = self
      .conn
      .prepare("SELECT id, contents, mime FROM clipboard ORDER BY id DESC")
      .map_err(|e| StashError::ListDecode(e.to_string()))?;
    let mut rows = stmt
      .query([])
      .map_err(|e| StashError::ListDecode(e.to_string()))?;

    let mut entries = Vec::new();

    while let Some(row) = rows
      .next()
      .map_err(|e| StashError::ListDecode(e.to_string()))?
    {
      let id: u64 = row
        .get(0)
        .map_err(|e| StashError::ListDecode(e.to_string()))?;
      let contents: Vec<u8> = row
        .get(1)
        .map_err(|e| StashError::ListDecode(e.to_string()))?;
      let mime: Option<String> = row
        .get(2)
        .map_err(|e| StashError::ListDecode(e.to_string()))?;
      let contents_str = match mime.as_deref() {
        Some(m) if m.starts_with("text/") || m == "application/json" => {
          String::from_utf8_lossy(&contents).to_string()
        },
        _ => STANDARD.encode(&contents),
      };
      entries.push(json!({
          "id": id,
          "contents": contents_str,
          "mime": mime,
      }));
    }

    serde_json::to_string_pretty(&entries)
      .map_err(|e| StashError::ListDecode(e.to_string()))
  }
}

impl ClipboardDb for SqliteClipboardDb {
  fn store_entry(
    &self,
    mut input: impl Read,
    max_dedupe_search: u64,
    max_items: u64,
  ) -> Result<u64, StashError> {
    let mut buf = Vec::new();
    if input.read_to_end(&mut buf).is_err()
      || buf.is_empty()
      || buf.len() > 5 * 1_000_000
    {
      return Err(StashError::EmptyOrTooLarge);
    }
    if buf.iter().all(u8::is_ascii_whitespace) {
      return Err(StashError::AllWhitespace);
    }

    let mime = match detect_mime(&buf) {
      None => {
        // If valid UTF-8, treat as text/plain
        if std::str::from_utf8(&buf).is_ok() {
          Some("text/plain".to_string())
        } else {
          None
        }
      },
      other => other,
    };

    // Try to load regex from systemd credential file, then env var
    let regex = load_sensitive_regex();
    if let Some(re) = regex {
      // Only check text data
      if let Ok(s) = std::str::from_utf8(&buf) {
        if re.is_match(s) {
          warn!("Clipboard entry matches sensitive regex, skipping store.");
          return Err(StashError::Store(
            "Filtered by sensitive regex".to_string(),
          ));
        }
      }
    }

    self.deduplicate(&buf, max_dedupe_search)?;

    self
      .conn
      .execute(
        "INSERT INTO clipboard (contents, mime) VALUES (?1, ?2)",
        params![buf, mime],
      )
      .map_err(|e| StashError::Store(e.to_string()))?;

    self.trim_db(max_items)?;
    Ok(self.next_sequence())
  }

  fn deduplicate(&self, buf: &[u8], max: u64) -> Result<usize, StashError> {
    let mut stmt = self
      .conn
      .prepare("SELECT id, contents FROM clipboard ORDER BY id DESC LIMIT ?1")
      .map_err(|e| StashError::DeduplicationRead(e.to_string()))?;
    let mut rows = stmt
      .query(params![i64::try_from(max).unwrap_or(i64::MAX)])
      .map_err(|e| StashError::DeduplicationRead(e.to_string()))?;
    let mut deduped = 0;
    while let Some(row) = rows
      .next()
      .map_err(|e| StashError::DeduplicationRead(e.to_string()))?
    {
      let id: u64 = row
        .get(0)
        .map_err(|e| StashError::DeduplicationDecode(e.to_string()))?;
      let contents: Vec<u8> = row
        .get(1)
        .map_err(|e| StashError::DeduplicationDecode(e.to_string()))?;
      if contents == buf {
        self
          .conn
          .execute("DELETE FROM clipboard WHERE id = ?1", params![id])
          .map_err(|e| StashError::DeduplicationRemove(e.to_string()))?;
        deduped += 1;
      }
    }
    Ok(deduped)
  }

  fn trim_db(&self, max: u64) -> Result<(), StashError> {
    let count: u64 = self
      .conn
      .query_row("SELECT COUNT(*) FROM clipboard", [], |row| row.get(0))
      .map_err(|e| StashError::Trim(e.to_string()))?;
    if count > max {
      let to_delete = count - max;
      self
        .conn
        .execute(
          "DELETE FROM clipboard WHERE id IN (SELECT id FROM clipboard ORDER \
           BY id ASC LIMIT ?1)",
          params![i64::try_from(to_delete).unwrap_or(i64::MAX)],
        )
        .map_err(|e| StashError::Trim(e.to_string()))?;
    }
    Ok(())
  }

  fn delete_last(&self) -> Result<(), StashError> {
    let id: Option<u64> = self
      .conn
      .query_row(
        "SELECT id FROM clipboard ORDER BY id DESC LIMIT 1",
        [],
        |row| row.get(0),
      )
      .optional()
      .map_err(|e| StashError::DeleteLast(e.to_string()))?;
    if let Some(id) = id {
      self
        .conn
        .execute("DELETE FROM clipboard WHERE id = ?1", params![id])
        .map_err(|e| StashError::DeleteLast(e.to_string()))?;
      Ok(())
    } else {
      Err(StashError::NoEntriesToDelete)
    }
  }

  fn wipe_db(&self) -> Result<(), StashError> {
    self
      .conn
      .execute("DELETE FROM clipboard", [])
      .map_err(|e| StashError::Wipe(e.to_string()))?;
    self
      .conn
      .execute("DELETE FROM sqlite_sequence WHERE name = 'clipboard'", [])
      .map_err(|e| StashError::Wipe(e.to_string()))?;
    Ok(())
  }

  fn list_entries(
    &self,
    mut out: impl Write,
    preview_width: u32,
  ) -> Result<usize, StashError> {
    let mut stmt = self
      .conn
      .prepare("SELECT id, contents, mime FROM clipboard ORDER BY id DESC")
      .map_err(|e| StashError::ListDecode(e.to_string()))?;
    let mut rows = stmt
      .query([])
      .map_err(|e| StashError::ListDecode(e.to_string()))?;
    let mut listed = 0;
    while let Some(row) = rows
      .next()
      .map_err(|e| StashError::ListDecode(e.to_string()))?
    {
      let id: u64 = row
        .get(0)
        .map_err(|e| StashError::ListDecode(e.to_string()))?;
      let contents: Vec<u8> = row
        .get(1)
        .map_err(|e| StashError::ListDecode(e.to_string()))?;
      let mime: Option<String> = row
        .get(2)
        .map_err(|e| StashError::ListDecode(e.to_string()))?;
      let preview = preview_entry(&contents, mime.as_deref(), preview_width);
      if writeln!(out, "{id}\t{preview}").is_ok() {
        listed += 1;
      }
    }
    Ok(listed)
  }

  fn decode_entry(
    &self,
    mut in_: impl Read,
    mut out: impl Write,
    input: Option<String>,
  ) -> Result<(), StashError> {
    let s = if let Some(input) = input {
      input
    } else {
      let mut buf = String::new();
      in_
        .read_to_string(&mut buf)
        .map_err(|e| StashError::DecodeRead(e.to_string()))?;
      buf
    };
    let id =
      extract_id(&s).map_err(|e| StashError::DecodeExtractId(e.to_string()))?;
    let (contents, _mime): (Vec<u8>, Option<String>) = self
      .conn
      .query_row(
        "SELECT contents, mime FROM clipboard WHERE id = ?1",
        params![id],
        |row| Ok((row.get(0)?, row.get(1)?)),
      )
      .map_err(|e| StashError::DecodeGet(e.to_string()))?;
    out
      .write_all(&contents)
      .map_err(|e| StashError::DecodeWrite(e.to_string()))?;
    info!("Decoded entry with id {id}");
    Ok(())
  }

  fn delete_query(&self, query: &str) -> Result<usize, StashError> {
    let mut stmt = self
      .conn
      .prepare("SELECT id, contents FROM clipboard")
      .map_err(|e| StashError::QueryDelete(e.to_string()))?;
    let mut rows = stmt
      .query([])
      .map_err(|e| StashError::QueryDelete(e.to_string()))?;
    let mut deleted = 0;
    while let Some(row) = rows
      .next()
      .map_err(|e| StashError::QueryDelete(e.to_string()))?
    {
      let id: u64 = row
        .get(0)
        .map_err(|e| StashError::QueryDelete(e.to_string()))?;
      let contents: Vec<u8> = row
        .get(1)
        .map_err(|e| StashError::QueryDelete(e.to_string()))?;
      if contents.windows(query.len()).any(|w| w == query.as_bytes()) {
        self
          .conn
          .execute("DELETE FROM clipboard WHERE id = ?1", params![id])
          .map_err(|e| StashError::QueryDelete(e.to_string()))?;
        deleted += 1;
      }
    }
    Ok(deleted)
  }

  fn delete_entries(&self, in_: impl Read) -> Result<usize, StashError> {
    let reader = BufReader::new(in_);
    let mut deleted = 0;
    for line in reader.lines().map_while(Result::ok) {
      if let Ok(id) = extract_id(&line) {
        self
          .conn
          .execute("DELETE FROM clipboard WHERE id = ?1", params![id])
          .map_err(|e| StashError::DeleteEntry(id, e.to_string()))?;
        deleted += 1;
      }
    }
    Ok(deleted)
  }

  fn next_sequence(&self) -> u64 {
    match self
      .conn
      .query_row("SELECT MAX(id) FROM clipboard", [], |row| {
        row.get::<_, Option<u64>>(0)
      }) {
      Ok(Some(max_id)) => max_id + 1,
      Ok(None) | Err(_) => 1,
    }
  }
}

// Helper functions

/// Try to load a sensitive regex from systemd credential or env.
///
/// # Returns
///  `Some(Regex)` if present and valid, `None` otherwise.
fn load_sensitive_regex() -> Option<Regex> {
  if let Ok(regex_path) = env::var("CREDENTIALS_DIRECTORY") {
    let file = format!("{regex_path}/clipboard_filter");
    if let Ok(contents) = fs::read_to_string(&file) {
      if let Ok(re) = Regex::new(contents.trim()) {
        return Some(re);
      }
    }
  }

  // Fallback to an environment variable
  if let Ok(pattern) = env::var("STASH_SENSITIVE_REGEX") {
    if let Ok(re) = Regex::new(&pattern) {
      return Some(re);
    }
  }

  None
}

pub fn extract_id(input: &str) -> Result<u64, &'static str> {
  let id_str = input.split('\t').next().unwrap_or("");
  id_str.parse().map_err(|_| "invalid id")
}

pub fn detect_mime(data: &[u8]) -> Option<String> {
  if let Ok(img_type) = imagesize::image_type(data) {
    Some(
      match img_type {
        ImageType::Png => "image/png",
        ImageType::Jpeg => "image/jpeg",
        ImageType::Gif => "image/gif",
        ImageType::Bmp => "image/bmp",
        ImageType::Tiff => "image/tiff",
        ImageType::Webp => "image/webp",
        ImageType::Aseprite => "image/x-aseprite",
        ImageType::Dds => "image/vnd.ms-dds",
        ImageType::Exr => "image/aces",
        ImageType::Farbfeld => "image/farbfeld",
        ImageType::Hdr => "image/vnd.radiance",
        ImageType::Ico => "image/x-icon",
        ImageType::Ilbm => "image/ilbm",
        ImageType::Jxl => "image/jxl",
        ImageType::Ktx2 => "image/ktx2",
        ImageType::Pnm => "image/x-portable-anymap",
        ImageType::Psd => "image/vnd.adobe.photoshop",
        ImageType::Qoi => "image/qoi",
        ImageType::Tga => "image/x-tga",
        ImageType::Vtf => "image/x-vtf",
        ImageType::Heif(_) => "image/heif",
        _ => "application/octet-stream",
      }
      .to_string(),
    )
  } else {
    None
  }
}

pub fn preview_entry(data: &[u8], mime: Option<&str>, width: u32) -> String {
  if let Some(mime) = mime {
    if mime.starts_with("image/") {
      if let Ok(ImageSize {
        width: img_width,
        height: img_height,
      }) = imagesize::blob_size(data)
      {
        return format!(
          "[[ binary data {} {} {}x{} ]]",
          size_str(data.len()),
          mime,
          img_width,
          img_height
        );
      }
    } else if mime == "application/json" || mime.starts_with("text/") {
      let s = match str::from_utf8(data) {
        Ok(s) => s,
        Err(e) => {
          error!("Failed to decode UTF-8 clipboard data: {e}");
          ""
        },
      };
      let s = s.trim().replace(|c: char| c.is_whitespace(), " ");
      return truncate(&s, width as usize, "…");
    }
  }
  let s = String::from_utf8_lossy(data);
  truncate(s.trim(), width as usize, "…")
}

pub fn truncate(s: &str, max: usize, ellip: &str) -> String {
  if s.chars().count() > max {
    s.chars().take(max).collect::<String>() + ellip
  } else {
    s.to_string()
  }
}

pub fn size_str(size: usize) -> String {
  let units = ["B", "KiB", "MiB"];
  let mut fsize = if let Ok(val) = u32::try_from(size) {
    f64::from(val)
  } else {
    error!("Clipboard entry size too large for display: {size}");
    f64::from(u32::MAX)
  };
  let mut i = 0;
  while fsize >= 1024.0 && i < units.len() - 1 {
    fsize /= 1024.0;
    i += 1;
  }
  format!("{:.0} {}", fsize, units[i])
}