Correctly interpret and change values; does not write yet

4 files changed, 118 insertions, 43 deletions

diff --git a/src/encoding.rs b/src/encoding.rs
index c117cd0..fc0c335 100644
--- a/src/encoding.rs
+++ b/src/encoding.rs
@@ -1,4 +1,6 @@
 use std::convert::TryFrom;
+use std::io;
+use crate::error::IntoIOError;
 use crate::util::read_big_endian;
 
 macro_rules! guard {
@@ -42,10 +44,13 @@ 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) -> io::Result<String> {
+    latin1
+        .chars()
+        .map(|c| u8::try_from(u32::from(c)))
+        .collect::<Result<Vec<u8>, _>>()
+        .map_err(|e| e.ioerr())
+        .and_then(|v| std::str::from_utf8(&v)
+                        .map(|s| s.to_string())
+                        .map_err(|e| e.ioerr()))
 }
diff --git a/src/id3v2.rs b/src/id3v2.rs
index 934bdf3..9e07cd3 100644
--- a/src/id3v2.rs
+++ b/src/id3v2.rs
@@ -26,6 +26,28 @@ fn parse_id3v2_header(bytes: &[u8]) -> Option<(u16, u8, usize)> {
     }
 }
 
+/// Encodes native string to ID3v2 string encoding (either Latin-1 or UCS-2 according to the
+/// characters used).
+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(ArrayIter2::new([0xfe, 0xff]))  // BOM
+                .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())
+}
+
 #[derive(Debug)]
 pub struct ID3v2 {
     header_size: usize,
@@ -115,25 +137,6 @@ impl RawFrame {
         }
     }
 
-    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);
 
@@ -147,12 +150,12 @@ impl RawFrame {
         }
     }
 
-    pub fn map_string<F: Fn(String) -> String>(self, f: F) -> io::Result<Option<Self>> {
+    pub fn map_string<F: FnOnce(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)?,
+                body: encode_string(&body)?,
             })
         };
 
@@ -162,7 +165,35 @@ impl RawFrame {
             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)),
+            None => Ok(None),
+        }
+    }
+
+    pub fn get_id(&self) -> &str {
+        &self.id
+    }
+}
+
+impl Frame {
+    pub fn to_raw(self) -> io::Result<RawFrame> {
+        let type_t = |typ: &str, body: String| Ok(RawFrame { id: typ.to_string(), flags: 0, body: encode_string(&body)? });
+
+        match self {
+            Self::TIT2(s) => type_t("TIT2", s),
+            Self::TYER(s) => type_t("TYER", s),
+            Self::TPE1(s) => type_t("TPE1", s),
+            Self::TALB(s) => type_t("TALB", s),
+            Self::TRCK(s) => type_t("TRCK", s),
+        }
+    }
+
+    pub fn id(&self) -> &str {
+        match self {
+            Frame::TIT2(_) => "TIT2",
+            Frame::TYER(_) => "TYER",
+            Frame::TPE1(_) => "TPE1",
+            Frame::TALB(_) => "TALB",
+            Frame::TRCK(_) => "TRCK",
         }
     }
 }
diff --git a/src/main.rs b/src/main.rs
index 63bbbf0..c2b4c5a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,8 +1,9 @@
 use std::io;
 use std::fs::File;
-use argparse::{ArgumentParser, StoreTrue, Store};
-use crate::options::Options;
+use argparse::{ArgumentParser, Store, StoreTrue, StoreOption};
+use crate::error::IntoIOError;
 use crate::id3v2::{ID3v2, Frame};
+use crate::options::Options;
 
 mod encoding;
 mod error;
@@ -22,11 +23,11 @@ fn parse_options_into(opt: &mut Options) {
         .add_option(&["--assume-utf8"], StoreTrue,
                     "Assume that all strings specified in the MP3 as Latin-1 are really UTF-8.");
 
-    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 opt.set_tags.album) .add_option(&["-A", "--album"],  StoreOption, "Set/replace album");
+    ap.refer(&mut opt.set_tags.artist).add_option(&["-a", "--artist"], StoreOption, "Set/replace artist");
+    ap.refer(&mut opt.set_tags.title) .add_option(&["-t", "--title"],  StoreOption, "Set/replace title");
+    ap.refer(&mut opt.set_tags.track) .add_option(&["-T", "--track"],  StoreOption, "Set/replace track number (num or num/num)");
+    ap.refer(&mut opt.set_tags.year)  .add_option(&["-y", "--year"],   StoreOption, "Set/replace year");
 
     ap.refer(&mut opt.file)
         .required()
@@ -58,14 +59,52 @@ fn print_tag(tag: &ID3v2) -> io::Result<()> {
     Ok(())
 }
 
+fn modify_tag(tag: &mut ID3v2, new_frame: Frame) -> io::Result<()> {
+    let mut indices = Vec::new();
+    for (i, frame) in tag.frames.iter().enumerate() {
+        if frame.get_id() == new_frame.id() {
+            indices.push(i);
+        }
+    }
+
+    match indices.len() {
+        0 => {
+            tag.frames.push(new_frame.to_raw()?);
+        }
+
+        1 => {
+            tag.frames[indices[0]] = new_frame.to_raw()?;
+        }
+
+        _ => {
+            return Err(format!("Multiple frames of type {} found", new_frame.id()).ioerr());
+        }
+    }
+
+    Ok(())
+}
+
 fn main() -> io::Result<()> {
     let options = parse_options();
 
-    let tag = ID3v2::from_stream(&mut File::open(options.file)?)?;
+    let mut tag = ID3v2::from_stream(&mut File::open(options.file)?)?;
     // println!("{:?}", tag);
 
-    // TODO: apply changes from options here
-    // Use RawFrame::map_string
+    if options.latin1_as_utf8 {
+        for frame in &mut tag.frames {
+            if let Some(new_frame) =
+                    frame.map_string(|s| encoding::from_utf8_mistaken_as_latin1(&s)
+                                            .expect("String cannot be encoded in ID3v2 (outside of Unicode BMP)"))? {
+                *frame = new_frame;
+            }
+        }
+    }
+
+    if let Some(s) = options.set_tags.album  { modify_tag(&mut tag, Frame::TALB(s))?; }
+    if let Some(s) = options.set_tags.artist { modify_tag(&mut tag, Frame::TPE1(s))?; }
+    if let Some(s) = options.set_tags.title  { modify_tag(&mut tag, Frame::TIT2(s))?; }
+    if let Some(s) = options.set_tags.track  { modify_tag(&mut tag, Frame::TRCK(s))?; }
+    if let Some(s) = options.set_tags.year   { modify_tag(&mut tag, Frame::TYER(s))?; }
 
     print_tag(&tag)?;
 
diff --git a/src/options.rs b/src/options.rs
index ceba05d..5f1dec9 100644
--- a/src/options.rs
+++ b/src/options.rs
@@ -7,11 +7,11 @@ pub struct Options {
 
 #[derive(Default)]
 pub struct TagOptions {
-    pub album: String,
-    pub artist: String,
-    pub title: String,
-    pub track: String,
-    pub year: String,
+    pub album: Option<String>,
+    pub artist: Option<String>,
+    pub title: Option<String>,
+    pub track: Option<String>,
+    pub year: Option<String>,
 }
 
 impl Default for Options {