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// SPDX-FileCopyrightText: 2021-2022 Lynnesbian
// SPDX-License-Identifier: GPL-3.0-or-later

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

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

impl Findings {
	/// Returns the recommended extension for this file, if known.
	pub fn recommended_extension(&self) -> Option<String> {
		mime_extension_lookup(self.mime.essence_str().into()).map(|extensions| extensions[0].clone())
	}

	/// Returns the recommended path for this file - i.e. what it should be renamed to - if known.
	pub fn recommended_path(&self) -> Option<PathBuf> {
		self
			.recommended_extension()
			.map(|ext| self.file.with_extension(ext.as_str()))
	}
}

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
		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()
	}
}

/// Errors that can occur while scanning a file with [`scan_file`](crate::files::scan_file).
#[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 MIME type 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(),
			}
		)
	}
}