sourcemap 0.3.0

use std::io;
use std::io::Read;

use base64;
use serde_json;
use serde_json::Value;

use jsontypes::RawSourceMap;
use types::{RawToken, Token, SourceMap, SourceMapIndex, SourceMapSection};
use errors::{Result, Error};

const DATA_PREABLE: &'static str = "data:application/json;base64,";
const B64: [i8; 123] = [
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57,
    58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
    9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1,
    -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
    39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
];

#[derive(PartialEq)]
enum HeaderState {
    Undecided,
    Junk,
    AwaitingNewline,
    PastHeader,
}


pub struct StripHeaderReader<R: Read> {
    r: R,
    header_state: HeaderState,
}

impl<R: Read> StripHeaderReader<R> {
    pub fn new(reader: R) -> StripHeaderReader<R> {
        StripHeaderReader {
            r: reader,
            header_state: HeaderState::Undecided,
        }
    }
}

fn is_junk_json(byte: u8) -> bool {
    byte == b')' || byte == b']' || byte == b'}' || byte == b'\''
}

impl<R: Read> Read for StripHeaderReader<R> {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        if self.header_state == HeaderState::PastHeader {
            return self.r.read(buf);
        }

        let mut backing = vec![0; buf.len()];
        let mut local_buf : &mut [u8] = &mut *backing;

        loop {
            let read = try!(self.r.read(local_buf));
            if read == 0 {
                return Ok(0);
            }
            for (offset, &byte) in local_buf[0..read].iter().enumerate() {
                self.header_state = match self.header_state {
                    HeaderState::Undecided => {
                        if is_junk_json(byte) {
                            HeaderState::Junk
                        } else {
                            (&mut buf[..read]).copy_from_slice(&local_buf[..read]);
                            self.header_state = HeaderState::PastHeader;
                            return Ok(read);
                        }
                    },
                    HeaderState::Junk => {
                        if byte == b'\r' {
                            HeaderState::AwaitingNewline
                        } else if byte == b'\n' {
                            HeaderState::PastHeader
                        } else {
                            HeaderState::Junk
                        }
                    },
                    HeaderState::AwaitingNewline => {
                        if byte == b'\n' {
                            HeaderState::PastHeader
                        } else {
                            fail!(io::Error::new(io::ErrorKind::InvalidData,
                                                 "expected newline"));
                        }
                    },
                    HeaderState::PastHeader => {
                        let rem = read - offset;
                        (&mut buf[..rem]).copy_from_slice(&local_buf[offset..read]);
                        return Ok(rem);
                    }
                };
            }
        }
    }
}


pub fn parse_vlq_segment(segment: &str) -> Result<Vec<i64>> {
    let mut rv = vec![];

    let mut cur = 0;
    let mut shift = 0;

    for c in segment.bytes() {
        let enc = B64[c as usize] as i64;
        let val = enc & 0b11111;
        let cont = enc >> 5;
        cur += val << shift;
        shift += 5;

        if cont == 0 {
            let sign = cur & 1;
            cur = cur >> 1;
            if sign != 0 {
                cur = -cur;
            }
            rv.push(cur);
            cur = 0;
            shift = 0;
        }
    }

    if cur != 0 || shift != 0 {
        Err(Error::VlqLeftover)
    } else if rv.len() == 0 {
        Err(Error::VlqNoValues)
    } else {
        Ok(rv)
    }
}

/// Represents the result of a decode operation
pub enum DecodedMap {
    /// Indicates a regular sourcemap
    Regular(SourceMap),
    /// Indicates a sourcemap index
    Index(SourceMapIndex),
}

impl DecodedMap {

    /// Shortcut to look up a token on either an index or a
    /// regular sourcemap.  This method can only be used if
    /// the contained index actually contains embedded maps
    /// or it will not be able to look up anything.
    pub fn lookup_token<'a>(&'a self, line: u32, col: u32) -> Option<Token<'a>> {
        match *self {
            DecodedMap::Regular(ref sm) => sm.lookup_token(line, col),
            DecodedMap::Index(ref smi) => smi.lookup_token(line, col),
        }
    }
}

fn decode_regular(rsm: RawSourceMap) -> Result<SourceMap> {
    let mut dst_col;
    let mut src_id;
    let mut src_line = 0;
    let mut src_col = 0;
    let mut name_id = 0;

    let mut tokens = vec![];
    let mut index = vec![];

    for (dst_line, line) in rsm.mappings.split(';').enumerate() {
        let mut line_index = vec![];
        dst_col = 0;

        for segment in line.split(',') {
            if segment.len() == 0 {
                continue;
            }

            let nums = try!(parse_vlq_segment(segment));
            dst_col = (dst_col as i64 + nums[0]) as u32;

            let mut src = !0;
            let mut name = !0;

            if nums.len() > 1 {
                if nums.len() != 4 && nums.len() != 5 {
                    fail!(Error::BadSegmentSize(nums.len() as u32));
                }
                src_id = nums[1] as u32;
                if src_id >= rsm.sources.len() as u32 {
                    fail!(Error::BadSourceReference(src_id));
                }

                src = src_id;
                src_line = (src_line as i64 + nums[2]) as u32;
                src_col = (src_col as i64 + nums[3]) as u32;

                if nums.len() > 4 {
                    name_id = (name_id as i64 + nums[4]) as u32;
                    if name_id >= rsm.names.len() as u32 {
                        fail!(Error::BadNameReference(name_id));
                    }
                    name = name_id as u32;
                }
            }

            tokens.push(RawToken {
                dst_line: dst_line as u32,
                dst_col: dst_col,
                src_line: src_line,
                src_col: src_col,
                src_id: src,
                name_id: name,
            });
            line_index.push((dst_col, (tokens.len() - 1) as u32));
        }

        line_index.sort();
        for (dst_col, token_id) in line_index {
            index.push((dst_line as u32, dst_col, token_id));
        }
    }

    let mut sources = rsm.sources;
    if let Some(source_root) = rsm.source_root {
        if !source_root.is_empty() {
            let source_root = source_root.trim_right_matches('/');
            sources = sources.into_iter().map(|x| {
                if x.len() > 0 && (x.starts_with('/') ||
                                   x.starts_with("http:") ||
                                   x.starts_with("https:")) {
                    x
                } else {
                    format!("{}/{}", source_root, x)
                }
            }).collect();
        }
    }

    // apparently we can encounter some non string types in real world
    // sourcemaps :(
    let names = rsm.names.into_iter().map(|val| {
        match val {
            Value::String(s) => s,
            Value::U64(i) => format!("{}", i),
            _ => "".into(),
        }
    }).collect::<Vec<String>>();

    Ok(SourceMap::new(
        rsm.version, rsm.file, tokens, index, names, sources,
        rsm.sources_content))
}

fn decode_index(rsm: RawSourceMap) -> Result<SourceMapIndex> {
    let mut sections = vec![];

    for mut raw_section in rsm.sections.unwrap_or(vec![]) {
        sections.push(SourceMapSection::new(
            (raw_section.offset.line, raw_section.offset.column),
            raw_section.url,
            match raw_section.map.take() {
                Some(map) => Some(try!(decode_regular(*map))),
                None => None,
            }
        ));
    }

    Ok(SourceMapIndex::new(
        rsm.version, rsm.file, sections))
}

/// Decodes a sourcemap or sourcemap index from a reader
///
/// This supports both sourcemaps and sourcemap indexes unless the
/// specialized methods on the individual types.
pub fn decode<R: Read>(rdr: R) -> Result<DecodedMap> {
    let mut rdr = StripHeaderReader::new(rdr);
    let rsm : RawSourceMap = try!(serde_json::from_reader(&mut rdr));

    Ok(if rsm.sections.is_some() {
        DecodedMap::Index(try!(decode_index(rsm)))
    } else {
        DecodedMap::Regular(try!(decode_regular(rsm)))
    })
}

/// Loads a sourcemap from a data URL.
pub fn decode_data_url(url: &str) -> Result<DecodedMap> {
    if !url.starts_with(DATA_PREABLE) {
        fail!(Error::InvalidDataUrl);
    }
    let data_b64 = &url.as_bytes()[DATA_PREABLE.len()..];
    let data = try!(base64::u8de(data_b64).map_err(|_| Error::InvalidDataUrl));
    decode(&data[..])
}