Even more stuff

5 files changed, 132 insertions, 82 deletions

diff --git a/src/encoding.rs b/src/encoding.rs
index a3851aa..c117cd0 100644
--- a/src/encoding.rs
+++ b/src/encoding.rs
@@ -42,10 +42,10 @@ pub fn from_ucs_2_bom(bytes: &[u8]) -> Option<String> {
     Some(res)
 }
 
-// pub fn from_utf8_mistaken_as_latin1(latin1: &str) -> Option<String> {
-//     guard!(latin1.chars().all(|c| (c as usize) < 256));
-//     match std::str::from_utf8(latin1.as_bytes()) {
-//         Ok(res) => Some(res.to_string()),
-//         Err(_) => None,
-//     }
-// }
+pub fn from_utf8_mistaken_as_latin1(latin1: &str) -> Option<String> {
+    guard!(latin1.chars().all(|c| (c as usize) < 256));
+    match std::str::from_utf8(latin1.as_bytes()) {
+        Ok(res) => Some(res.to_string()),
+        Err(_) => None,
+    }
+}
diff --git a/src/error.rs b/src/error.rs
index 6358bfe..19bd48d 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -4,19 +4,8 @@ pub trait IntoIOError {
     fn ioerr(self) -> io::Error;
 }
 
-impl IntoIOError for String {
-    fn ioerr(self) -> io::Error {
-        io::Error::new(io::ErrorKind::Other, self)
-    }
-}
-
-impl IntoIOError for &str {
-    fn ioerr(self) -> io::Error {
-        io::Error::new(io::ErrorKind::Other, self)
-    }
-}
-
-impl IntoIOError for std::string::FromUtf8Error {
+// This impl bound is taken directly from the io::Error::new function.
+impl<E: Into<Box<dyn std::error::Error + Send + Sync>>> IntoIOError for E {
     fn ioerr(self) -> io::Error {
         io::Error::new(io::ErrorKind::Other, self)
     }
diff --git a/src/id3v2.rs b/src/id3v2.rs
index a8dccb9..934bdf3 100644
--- a/src/id3v2.rs
+++ b/src/id3v2.rs
@@ -1,9 +1,11 @@
 // http://id3.org/id3v2.3.0
 
+use std::convert::TryFrom;
 use std::io::{self, Read};
+use std::iter;
+use std::num::TryFromIntError;
 use crate::encoding::{from_latin_1, from_ucs_2_bom};
 use crate::error::IntoIOError;
-use crate::options::EncodingOptions;
 use crate::util::read_big_endian;
 
 fn parse_id3v2_header(bytes: &[u8]) -> Option<(u16, u8, usize)> {
@@ -46,6 +48,30 @@ pub enum Frame {
     TRCK(String),
 }
 
+struct ArrayIter2<T> {
+    arr: [T; 2],
+    cursor: u8,
+}
+
+impl<T> ArrayIter2<T> {
+    fn new(arr: [T; 2]) -> Self {
+        Self { arr, cursor: 0 }
+    }
+}
+
+impl<T: Clone> Iterator for ArrayIter2<T> {
+    type Item = T;
+    fn next(&mut self) -> Option<T> {
+        if (self.cursor as usize) < self.arr.len() {
+            let i = self.cursor;
+            self.cursor += 1;
+            Some(self.arr[i as usize].clone())
+        } else {
+            None
+        }
+    }
+}
+
 impl RawFrame {
     fn parse(data: &[u8]) -> Result<Option<(Self, usize)>, String> {
         if data.len() < 10 {
@@ -69,16 +95,12 @@ impl RawFrame {
         Ok(Some((RawFrame { id, flags, body }, 10 + size)))
     }
 
-    fn interpret_encoded_string(&self, encopts: &EncodingOptions) -> io::Result<String> {
+    fn interpret_encoded_string(&self) -> io::Result<String> {
         match self.body.get(0).ok_or("String field too small".ioerr())? {
             0 => {  // Latin-1
                 let mut i = self.body.len();
                 while i > 0 && self.body[i-1] == 0 { i -= 1; }
-                if encopts.latin1_as_utf8 {
-                    String::from_utf8(self.body[1..i].to_vec()).map_err(|e| e.ioerr())
-                } else {
-                    from_latin_1(&self.body[1..i]).ok_or("Invalid Latin-1 string field".ioerr())
-                }
+                from_latin_1(&self.body[1..i]).ok_or("Invalid Latin-1 string field".ioerr())
             }
 
             1 => {  // UCS-2
@@ -93,21 +115,56 @@ impl RawFrame {
         }
     }
 
-    pub fn interpret(&self, encopts: &EncodingOptions) -> io::Result<Option<Frame>> {
-        if self.id == "TIT2" {
-            self.interpret_encoded_string(encopts).map(Frame::TIT2).map(Some)
-        } else if self.id == "TYER" {
-            self.interpret_encoded_string(encopts).map(Frame::TYER).map(Some)
-        } else if self.id == "TPE1" {
-            self.interpret_encoded_string(encopts).map(Frame::TPE1).map(Some)
-        } else if self.id == "TALB" {
-            self.interpret_encoded_string(encopts).map(Frame::TALB).map(Some)
-        } else if self.id == "TRCK" {
-            self.interpret_encoded_string(encopts).map(Frame::TRCK).map(Some)
-        } else {
+    fn encode_string(s: &str) -> io::Result<Vec<u8>> {
+        let as_latin1 = || iter::once(Ok(0))
+                                .chain(s.chars().map(|c| u8::try_from(u32::from(c))))
+                                .collect::<Result<Vec<u8>, _>>();
+
+        let as_ucs2 = || {
+            let nibbles = s.chars()
+                                .map(|c| u16::try_from(u32::from(c)))
+                                .collect::<Result<Vec<u16>, _>>()?;
+            Ok(iter::once(1)
+                    .chain(nibbles.iter().flat_map(|&n| ArrayIter2::new([(n >> 8) as u8, n as u8])))
+                    .collect::<Vec<u8>>())
+        };
+
+        as_latin1()
+            .or_else(|_| as_ucs2())
+            .map_err(|e: TryFromIntError| e.ioerr())
+    }
+
+    pub fn interpret(&self) -> io::Result<Option<Frame>> {
+        let type_t = |typ: fn(String) -> Frame| self.interpret_encoded_string().map(typ).map(Some);
+
+        if      self.id == "TIT2" { type_t(Frame::TIT2) }
+        else if self.id == "TYER" { type_t(Frame::TYER) }
+        else if self.id == "TPE1" { type_t(Frame::TPE1) }
+        else if self.id == "TALB" { type_t(Frame::TALB) }
+        else if self.id == "TRCK" { type_t(Frame::TRCK) }
+        else {
             Ok(None)
         }
     }
+
+    pub fn map_string<F: Fn(String) -> String>(self, f: F) -> io::Result<Option<Self>> {
+        let type_t = |id: &str, body: String| -> io::Result<Self> {
+            Ok(Self {
+                id: id.to_string(),
+                flags: 0,
+                body: Self::encode_string(&body)?,
+            })
+        };
+
+        match self.interpret()? {
+            Some(Frame::TIT2(s)) => Ok(Some(type_t("TIT2", f(s))?)),
+            Some(Frame::TYER(s)) => Ok(Some(type_t("TYER", f(s))?)),
+            Some(Frame::TPE1(s)) => Ok(Some(type_t("TPE1", f(s))?)),
+            Some(Frame::TALB(s)) => Ok(Some(type_t("TALB", f(s))?)),
+            Some(Frame::TRCK(s)) => Ok(Some(type_t("TRCK", f(s))?)),
+            None => Ok(Some(self)),
+        }
+    }
 }
 
 impl ID3v2 {
diff --git a/src/main.rs b/src/main.rs
index 3939e17..63bbbf0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,8 @@
 use std::io;
 use std::fs::File;
 use argparse::{ArgumentParser, StoreTrue, Store};
-use crate::options::{EncodingOptions, Options};
+use crate::options::Options;
+use crate::id3v2::{ID3v2, Frame};
 
 mod encoding;
 mod error;
@@ -9,57 +10,64 @@ mod id3v2;
 mod options;
 mod util;
 
-fn main() -> io::Result<()> {
-    let options = {
-        let mut options: Options = Default::default();
+fn parse_options_into(opt: &mut Options) {
+    let mut ap = ArgumentParser::new();
+    ap.set_description("ID3v2 tag editor/fixer. Incomplete/work-in-progress.");
+
+    ap.refer(&mut opt.write)
+        .add_option(&["-w", "--write"], StoreTrue,
+                    "Write updated information instead of just displaying. Unmodified or unknown tags are preserved as-is.");
 
-        {
-            let mut ap = ArgumentParser::new();
-            ap.set_description("ID3v2 tag editor/fixer. Incomplete/work-in-progress.");
+    ap.refer(&mut opt.latin1_as_utf8)
+        .add_option(&["--assume-utf8"], StoreTrue,
+                    "Assume that all strings specified in the MP3 as Latin-1 are really UTF-8.");
 
-            ap.refer(&mut options.write)
-                .add_option(&["-w", "--write"], StoreTrue,
-                            "Write updated information instead of just displaying. Unmodified or unknown tags are preserved as-is.");
+    ap.refer(&mut opt.set_tags.album) .add_option(&["-A", "--album"],  Store, "Set/replace album");
+    ap.refer(&mut opt.set_tags.artist).add_option(&["-a", "--artist"], Store, "Set/replace artist");
+    ap.refer(&mut opt.set_tags.title) .add_option(&["-t", "--title"],  Store, "Set/replace title");
+    ap.refer(&mut opt.set_tags.track) .add_option(&["-T", "--track"],  Store, "Set/replace track number (num or num/num)");
+    ap.refer(&mut opt.set_tags.year)  .add_option(&["-y", "--year"],   Store, "Set/replace year");
 
-            ap.refer(&mut options.latin1_as_utf8)
-                .add_option(&["--assume-utf8"], StoreTrue,
-                            "Assume that all strings specified in the MP3 as Latin-1 are really UTF-8.");
+    ap.refer(&mut opt.file)
+        .required()
+        .add_argument("file", Store,
+                      "File to operate on (probably a .mp3)");
 
-            ap.refer(&mut options.set_tags.album) .add_option(&["-A", "--album"],  Store, "Set/replace album");
-            ap.refer(&mut options.set_tags.artist).add_option(&["-a", "--artist"], Store, "Set/replace artist");
-            ap.refer(&mut options.set_tags.title) .add_option(&["-t", "--title"],  Store, "Set/replace title");
-            ap.refer(&mut options.set_tags.track) .add_option(&["-T", "--track"],  Store, "Set/replace track number (num or num/num)");
-            ap.refer(&mut options.set_tags.year)  .add_option(&["-y", "--year"],   Store, "Set/replace year");
+    ap.parse_args_or_exit();
+}
 
-            ap.refer(&mut options.file)
-                .required()
-                .add_argument("file", Store,
-                              "File to operate on (probably a .mp3)");
+fn parse_options() -> Options {
+    let mut options = Default::default();
+    parse_options_into(&mut options);
+    options
+}
 
-            ap.parse_args_or_exit();
+fn print_tag(tag: &ID3v2) -> io::Result<()> {
+    for frame in &tag.frames {
+        match frame.interpret()? {
+            Some(Frame::TALB(album))  => println!("Album : '{}'", album),
+            Some(Frame::TIT2(title))  => println!("Title : '{}'", title),
+            Some(Frame::TPE1(artist)) => println!("Artist: '{}'", artist),
+            Some(Frame::TYER(year))   => println!("Year  : '{}'", year),
+            Some(Frame::TRCK(track))  => println!("Track : '{}'", track),
+            None => {
+                println!("Unknown frame: {:?}", frame);
+            }
         }
+    }
+    Ok(())
+}
 
-        options
-    };
+fn main() -> io::Result<()> {
+    let options = parse_options();
 
-    let mut f = File::open(options.file)?;
-    let tag = id3v2::ID3v2::from_stream(&mut f)?;
+    let tag = ID3v2::from_stream(&mut File::open(options.file)?)?;
     // println!("{:?}", tag);
 
     // TODO: apply changes from options here
+    // Use RawFrame::map_string
 
-    for frame in tag.frames {
-        match frame.interpret(&EncodingOptions { latin1_as_utf8: options.latin1_as_utf8 })? {
-            Some(id3v2::Frame::TALB(album))  => println!("Album : '{}'", album),
-            Some(id3v2::Frame::TIT2(title))  => println!("Title : '{}'", title),
-            Some(id3v2::Frame::TPE1(artist)) => println!("Artist: '{}'", artist),
-            Some(id3v2::Frame::TYER(year))   => println!("Year  : '{}'", year),
-            Some(id3v2::Frame::TRCK(track))  => println!("Track : '{}'", track),
-            None => {
-                println!("Unknown frame: {:?}", frame);
-            }
-        }
-    }
+    print_tag(&tag)?;
 
     // TODO: if -w, then write tags to file (if it fits)
 
diff --git a/src/options.rs b/src/options.rs
index e51004a..ceba05d 100644
--- a/src/options.rs
+++ b/src/options.rs
@@ -14,10 +14,6 @@ pub struct TagOptions {
     pub year: String,
 }
 
-pub struct EncodingOptions {
-    pub latin1_as_utf8: bool,
-}
-
 impl Default for Options {
     fn default() -> Self {
         Options {