//! The [`Findings`] and [`ScanError`] structs, used for conveying whether a given file was able to be scanned and
//! whether its MIME type could be inferred.

use std::cmp::Ordering;
use std::fmt::{Display, Formatter};
use std::path::{Path, PathBuf};

use mime::Mime;
#[cfg(feature = "json")]
use serde::{ser::SerializeStruct, Serializer};

use crate::files::mime_extension_lookup;
use crate::String;

/// Information about a scanned file.
#[derive(Eq, PartialEq)]
pub struct Findings {
	/// The location of the scanned file.
	pub file: PathBuf,
	/// Whether or not the file's extension is valid for its mimetype.
	pub valid: bool,
	/// The file's mimetype.
	pub mime: Mime,
}

impl PartialOrd<Self> for Findings {
	fn partial_cmp(&self, other: &Self) -> Option<Ordering> { Some(self.cmp(other)) }
}

impl Ord for Findings {
	fn cmp(&self, other: &Self) -> Ordering {
		// files with no recommended extension should appear first, so that fif outputs the "no known extension for x"
		// comments before the "mv x y" instructions
		// since fif doesn't output anything for valid files, the comparison will consider any comparison involving a
		// valid Findings to be equal, avoiding the (somewhat) expensive call to recommended_extension. after all, since
		// fif never displays valid files, it really doesn't matter what position they end up in.
		if self.valid || other.valid {
			return Ordering::Equal;
		}
		match (self.recommended_extension(), other.recommended_extension()) {
			(None, Some(_)) => Ordering::Greater,
			(Some(_), None) => Ordering::Less,
			_ => self.file.cmp(&other.file),
		}
	}
}

#[cfg(feature = "json")]
impl serde::Serialize for Findings {
	fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
	where
		S: Serializer,
	{
		// the second parameter is the number of fields in the struct -- in this case, 3
		let mut state = serializer.serialize_struct("Findings", 3)?;

		state.serialize_field("file", &self.file)?;
		state.serialize_field("valid", &self.valid)?;
		state.serialize_field("mime", &self.mime.essence_str())?;
		state.end()
	}
}

impl Findings {
	pub fn recommended_extension(&self) -> Option<String> {
		mime_extension_lookup(self.mime.essence_str().into()).map(|extensions| extensions[0].clone())
	}
}

#[derive(Debug, PartialEq, PartialOrd, Ord, Eq)]
#[cfg_attr(feature = "json", derive(serde::Serialize))]
#[cfg_attr(feature = "json", serde(tag = "type", content = "path"))]
pub enum ScanError<'a> {
	/// Something went wrong while trying to read the given file.
	File(&'a Path),
	/// Failed to determine the mimetype of the given file.
	Mime(&'a Path),
}

impl<'a> Display for ScanError<'a> {
	fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
		write!(
			f,
			"Couldn't {} file: {}",
			match self {
				Self::File(_) => "read",
				Self::Mime(_) => "determine mime type of",
			},
			match self {
				Self::File(f) | Self::Mime(f) => f.to_string_lossy(),
			}
		)
	}
}