From 526a4d60685ad1e00904c7a81c57cb2ef5970640 Mon Sep 17 00:00:00 2001
From: Muaz Ahmad <mahmad2000@protonmail.com>
Date: Thu, 5 Oct 2023 16:30:07 +0500
Subject: [PATCH] some basic implementations, file header skip, metadata read

---
 src/demux/flv.rs | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/src/demux/flv.rs b/src/demux/flv.rs
index f62b45b..5516c72 100644
--- a/src/demux/flv.rs
+++ b/src/demux/flv.rs
@@ -12,7 +12,7 @@ enum FLVTagType {
 }
 
 impl TryFrom<u8> for FLVTagType {
-    type Error = util::GenericError;
+    type Error = util::DemuxerError;
     fn try_from(type_byte: u8) -> Result<Self, Self::Error> {
         match type_byte {
             8 => Ok(FLVTagType::Audio),
@@ -28,6 +28,24 @@ pub struct FLVReader {
 }
 
 impl FLVReader {
+    fn check_signature(&mut self) -> Result<(), Box<dyn Error>> {
+        let mut sig_bytes_rem = [0u8; 3];
+        self.stdin.read_exact(&mut sig_bytes_rem)?;
+        if String::from_utf8(sig_bytes_rem[..2].to_vec())? != "LV" || sig_bytes_rem[2] != 1 {
+            return Err(Box::new(util::DemuxerError::FLVCheckFail))
+        }
+        Ok(())
+    }
+
+    fn skip_init_header(&mut self) -> Result<(), Box<dyn Error>> {
+        let mut rest_of_header = [0u8; 5];
+        self.stdin.read_exact(&mut rest_of_header)?;
+        let head_offset = u32::from_be_bytes(rest_of_header[1..].try_into()?) as usize + 4;
+        let mut skip_header_extra = vec![0u8; head_offset];
+        self.stdin.read_exact(skip_header_extra.as_mut_slice())?;
+        return Ok(());
+    }
+
     fn read_packet(&mut self) -> Result<(FLVTagType, Vec<u8>), Box<dyn Error>> {
         let mut tag_head = [0u8; 11];
         self.stdin.read_exact(&mut tag_head)?;
@@ -40,11 +58,21 @@ impl FLVReader {
 
         return Ok((tag_type, packet_data));
     }
+
+    fn read_metadata(&mut self) -> Result<util::Metadata, Box<dyn Error>> {
+        let (packet_type, packet_data) = self.read_packet()?;
+        match packet_type {
+            FLVTagType::Metadata => (),
+            x => return Err(Box::new(util::DemuxerError::FLVPacketNotMetadata))
+        }
+        return process_metadata(packet_data);
+    }
 }
 
 impl input::FileReader for FLVReader {
     fn init(&mut self) -> Result<util::Metadata, Box<dyn Error>> {
-        todo!();
+        self.skip_init_header();
+        return self.read_metadata()
     }
     fn read_nalu(&mut self) -> Result<util::NALUPacket, Box<dyn Error>> {
         todo!();
@@ -52,5 +80,11 @@ impl input::FileReader for FLVReader {
 }
 
 pub fn new_reader(stdin: io::Stdin) -> Result<FLVReader, Box<dyn Error>> {
+    let mut reader = FLVReader { stdin: stdin };
+    reader.check_signature()?;
+    return Ok(reader);
+}
+
+fn process_metadata(data: Vec<u8>) -> Result<util::Metadata, Box<dyn Error>> {
     todo!();
 }