subparse/formats/

ssa.rs

// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

use crate::{SubtitleEntry, SubtitleFileInterface};

use crate::errors::Result as SubtitleParserResult;
use crate::formats::common::*;
use combine::char::*;
use combine::combinator::*;
use combine::primitives::Parser;

use crate::timetypes::{TimePoint, TimeSpan};
use failure::ResultExt;
use std::iter::once;

type Result<T> = std::result::Result<T, Error>;

use self::errors::Error;
use self::errors::ErrorKind::*;

// Errors specific to the '.ssa' format.
#[allow(missing_docs)]
pub mod errors {

    define_error!(Error, ErrorKind);

    /// `.ssa`-parser-specific errors
    #[derive(PartialEq, Debug, Fail)]
    pub enum ErrorKind {
        #[fail(display = ".ssa/.ass file did not have a line beginning with `Format: ` in a `[Events]` section")]
        SsaFieldsInfoNotFound,

        #[fail(display = "the '{}' field is missing in the field info in line {}", f, line_num)]
        SsaMissingField { line_num: usize, f: &'static str },

        #[fail(display = "the '{}' field is twice in the field info in line {}", f, line_num)]
        SsaDuplicateField { line_num: usize, f: &'static str },

        #[fail(display = "the field info in line {} has to have `Text` as its last field", line_num)]
        SsaTextFieldNotLast { line_num: usize },

        #[fail(display = "the dialog at line {} has incorrect number of fields", line_num)]
        SsaIncorrectNumberOfFields { line_num: usize },

        #[fail(display = "the timepoint `{}` in line {} has wrong format", string, line_num)]
        SsaWrongTimepointFormat { line_num: usize, string: String },

        #[fail(display = "parsing the line `{}` failed because of `{}`", line_num, msg)]
        SsaDialogLineParseError { line_num: usize, msg: String },

        #[fail(display = "parsing the line `{}` failed because of `{}`", line_num, msg)]
        SsaLineParseError { line_num: usize, msg: String },
    }
}
/*error_chain! {
    errors {
        SsaFieldsInfoNotFound {
            description(".ssa/.ass file did not have a line beginning with `Format: ` in a `[Events]` section")
        }
        SsaMissingField(line_num: usize, f: &'static str) {
            display("the '{}' field is missing in the field info in line {}", f, line_num)
        }
        SsaDuplicateField(line_num: usize, f: &'static str) {
            display("the '{}' field is twice in the field info in line {}", f, line_num)
        }
        SsaTextFieldNotLast(line_num: usize) {
            display("the field info in line {} has to have `Text` as its last field", line_num)
        }
        SsaIncorrectNumberOfFields(line_num: usize) {
            display("the dialog at line {} has incorrect number of fields", line_num)
        }
        SsaWrongTimepointFormat(line_num: usize, string: String) {
            display("the timepoint `{}` in line {} has wrong format", string, line_num)
        }
        SsaDialogLineParseError(line_num: usize, msg: String) {
            display("parsing the line `{}` failed because of `{}`", line_num, msg)
        }
        SsaLineParseError(line_num: usize, msg: String) {
            display("parsing the line `{}` failed because of `{}`", line_num, msg)
        }
    }
}*/

// ////////////////////////////////////////////////////////////////////////////////////////////////
// SSA field info

struct SsaFieldsInfo {
    start_field_idx: usize,
    end_field_idx: usize,
    text_field_idx: usize,
    num_fields: usize,
}

impl SsaFieldsInfo {
    /// Parses a format line like "Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text".
    fn new_from_fields_info_line(line_num: usize, s: String) -> Result<SsaFieldsInfo> {
        assert!(s.starts_with("Format:"));
        let field_info = &s["Format:".len()..];
        let mut start_field_idx: Option<usize> = None;
        let mut end_field_idx: Option<usize> = None;
        let mut text_field_idx: Option<usize> = None;

        // filter "Start" and "End" and "Text"
        let split_iter = field_info.split(',');
        let num_fields = split_iter.clone().count();
        for (i, field_name) in split_iter.enumerate() {
            let trimmed = field_name.trim();
            if trimmed == "Start" {
                if start_field_idx.is_some() {
                    return Err(SsaDuplicateField { line_num, f: "Start" })?;
                }
                start_field_idx = Some(i);
            } else if trimmed == "End" {
                if end_field_idx.is_some() {
                    return Err(SsaDuplicateField { line_num, f: "End" })?;
                }
                end_field_idx = Some(i);
            } else if trimmed == "Text" {
                if text_field_idx.is_some() {
                    return Err(SsaDuplicateField { line_num, f: "Text" })?;
                }
                text_field_idx = Some(i);
            }
        }

        let text_field_idx2 = text_field_idx.ok_or_else(|| Error::from(SsaMissingField { line_num, f: "Text" }))?;
        if text_field_idx2 != num_fields - 1 {
            return Err(SsaTextFieldNotLast { line_num })?;
        }

        Ok(SsaFieldsInfo {
            start_field_idx: start_field_idx.ok_or_else(|| Error::from(SsaMissingField { line_num, f: "Start" }))?,
            end_field_idx: end_field_idx.ok_or_else(|| Error::from(SsaMissingField { line_num, f: "End" }))?,
            text_field_idx: text_field_idx2,
            num_fields: num_fields,
        })
    }
}

// ////////////////////////////////////////////////////////////////////////////////////////////////
// SSA parser

impl SsaFile {
    /// Parse a `.ssa` subtitle string to `SsaFile`.
    pub fn parse(s: &str) -> SubtitleParserResult<SsaFile> {
        Ok(Self::parse_inner(s.to_string()).with_context(|_| crate::ErrorKind::ParsingError)?)
    }
}

/// Implement parser helper functions.
impl SsaFile {
    /// Parses a whole `.ssa` file from string.
    fn parse_inner(i: String) -> Result<SsaFile> {
        let mut file_parts = Vec::new();
        let (bom, s) = split_bom(&i);
        file_parts.push(SsaFilePart::Filler(bom.to_string()));

        // first we need to find and parse the format line, which then dictates how to parse the file
        let (line_num, field_info_line) = Self::get_format_info(s)?;
        let fields_info = SsaFieldsInfo::new_from_fields_info_line(line_num, field_info_line)?;

        // parse the dialog lines with the given format
        file_parts.append(&mut Self::parse_dialog_lines(&fields_info, s)?);
        Ok(SsaFile::new(file_parts))
    }

    /// Searches and parses a format line like "Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text".
    fn get_format_info(s: &str) -> Result<(usize, String)> {
        let mut section_opt = None;
        for (line_num, line) in s.lines().enumerate() {
            // parse section headers like `[Events]`
            let trimmed_line = line.trim();
            if trimmed_line.starts_with('[') && trimmed_line.ends_with(']') {
                section_opt = Some(&trimmed_line[1..trimmed_line.len() - 1]);
            }

            // most sections have a format line, but we only want the one for the subtitle events
            if section_opt != Some("Events") {
                continue;
            }
            if !line.trim().starts_with("Format:") {
                continue;
            }
            return Ok((line_num, line.to_string()));
        }

        Err(SsaFieldsInfoNotFound.into())
    }

    /// Filters file for lines like this and parses them:
    ///
    /// ```text
    /// "Dialogue: 1,0:22:43.52,0:22:46.22,ED-Romaji,,0,0,0,,{\fad(150,150)\blur0.5\bord1}some text"
    /// ```
    fn parse_dialog_lines(fields_info: &SsaFieldsInfo, s: &str) -> Result<Vec<SsaFilePart>> {
        let mut result = Vec::new();
        let mut section_opt: Option<String> = None;

        for (line_num, (line, newl)) in get_lines_non_destructive(s).into_iter().enumerate() {
            let trimmed_line = line.trim().to_string();

            // parse section headers like `[Events]`
            if trimmed_line.starts_with('[') && trimmed_line.ends_with(']') {
                section_opt = Some(trimmed_line[1..trimmed_line.len() - 1].to_string());
                result.push(SsaFilePart::Filler(line));
                result.push(SsaFilePart::Filler("\n".to_string()));
                continue;
            }

            if section_opt.is_none() || section_opt.iter().any(|s| s != "Events") || !trimmed_line.starts_with("Dialogue:") {
                result.push(SsaFilePart::Filler(line));
                result.push(SsaFilePart::Filler("\n".to_string()));
                continue;
            }

            result.append(&mut Self::parse_dialog_line(line_num, line.as_str(), fields_info)?);
            result.push(SsaFilePart::Filler(newl));
        }

        Ok(result)
    }

    /// Parse lines like:
    ///
    /// ```text
    /// "Dialogue: 1,0:22:43.52,0:22:46.22,ED-Romaji,,0,0,0,,{\fad(150,150)\blur0.5\bord1}some text"
    /// ```
    fn parse_dialog_line(line_num: usize, line: &str, fields_info: &SsaFieldsInfo) -> Result<Vec<SsaFilePart>> {
        let parts_res = (
            many(ws()),
            string("Dialogue:"),
            many(ws()),
            count(fields_info.num_fields - 1, (many(none_of(once(','))), token(','))),
            many(r#try(any())),
        )
            .map(
                |(ws1, dl, ws2, v, text): (String, &str, String, Vec<(String, char)>, String)| -> Result<Vec<SsaFilePart>> {
                    let mut result: Vec<SsaFilePart> = Vec::new();
                    result.push(SsaFilePart::Filler(ws1));
                    result.push(SsaFilePart::Filler(dl.to_string()));
                    result.push(SsaFilePart::Filler(ws2.to_string()));
                    result.append(&mut Self::parse_fields(line_num, fields_info, v)?);
                    result.push(SsaFilePart::Text(text));
                    Ok(result)
                },
            )
            .parse(line);

        match parts_res {
            // Ok() means that parsing succeded, but the "map" function might created an SSA error
            Ok((parts, _)) => Ok(parts?),
            Err(e) => Err(SsaDialogLineParseError {
                line_num,
                msg: parse_error_to_string(e),
            }
            .into()),
        }
    }

    /// Parses an array of fields with the "fields info".
    ///
    /// The fields (comma seperated information) as an array like
    // `vec!["1", "0:22:43.52", "0:22:46.22", "ED-Romaji", "", "0", "0", "0", "", "{\fad(150,150)\blur0.5\bord1}some text"]`.
    fn parse_fields(line_num: usize, fields_info: &SsaFieldsInfo, v: Vec<(String, char)>) -> Result<Vec<SsaFilePart>> {
        let extract_file_parts_closure = |(i, (field, sep_char)): (_, (String, char))| -> Result<Vec<SsaFilePart>> {
            let (begin, field, end) = trim_non_destructive(&field);

            let part = if i == fields_info.start_field_idx {
                SsaFilePart::TimespanStart(Self::parse_timepoint(line_num, &field)?)
            } else if i == fields_info.end_field_idx {
                SsaFilePart::TimespanEnd(Self::parse_timepoint(line_num, &field)?)
            } else if i == fields_info.text_field_idx {
                SsaFilePart::Text(field.to_string())
            } else {
                SsaFilePart::Filler(field.to_string())
            };

            Ok(vec![
                SsaFilePart::Filler(begin),
                part,
                SsaFilePart::Filler(end),
                SsaFilePart::Filler(sep_char.to_string()),
            ])
        };

        let result = v
            .into_iter()
            .enumerate()
            .map(extract_file_parts_closure)
            .collect::<Result<Vec<Vec<SsaFilePart>>>>()?
            .into_iter()
            .flat_map(|part| part)
            .collect();
        Ok(result)
    }

    /// Something like "0:19:41.99"
    fn parse_timepoint(line_num: usize, s: &str) -> Result<TimePoint> {
        let parse_res = (
            parser(number_i64),
            token(':'),
            parser(number_i64),
            token(':'),
            parser(number_i64),
            or(token('.'), token(':')),
            parser(number_i64),
            eof(),
        )
            .map(|(h, _, mm, _, ss, _, ms, _)| TimePoint::from_components(h, mm, ss, ms * 10))
            .parse(s);
        match parse_res {
            Ok(res) => Ok(res.0),
            Err(e) => Err(SsaWrongTimepointFormat {
                line_num,
                string: parse_error_to_string(e),
            }
            .into()),
        }
    }
}

// ////////////////////////////////////////////////////////////////////////////////////////////////
// SSA file parts

#[derive(Debug, Clone)]
enum SsaFilePart {
    /// Spaces, field information, comments, unimportant fields, ...
    Filler(String),

    /// Timespan start of a dialogue line
    TimespanStart(TimePoint),

    /// Timespan end of a dialogue line
    TimespanEnd(TimePoint),

    /// Dialog lines
    Text(String),
}

// ////////////////////////////////////////////////////////////////////////////////////////////////
// SSA file

/// Represents a reconstructable `.ssa`/`.ass` file.
///
/// All unimportant information (for this project) are saved into `SsaFilePart::Filler(...)`, so
/// a timespan-altered file still has the same field etc.
#[derive(Debug, Clone)]
pub struct SsaFile {
    v: Vec<SsaFilePart>,
}

impl SsaFile {
    fn new(v: Vec<SsaFilePart>) -> SsaFile {
        // cleans up multiple fillers after another
        let new_file_parts = dedup_string_parts(v, |part: &mut SsaFilePart| match *part {
            SsaFilePart::Filler(ref mut text) => Some(text),
            _ => None,
        });

        SsaFile { v: new_file_parts }
    }

    /// This function filters out all start times and end times, and returns them ordered
    /// (="(start, end, dialog)") so they can be easily read or written to.
    ///
    /// TODO: implement a single version that takes both `&mut` and `&` (dependent on HKT).
    fn get_subtitle_entries_mut<'a>(&'a mut self) -> Vec<(&'a mut TimePoint, &'a mut TimePoint, &'a mut String)> {
        let mut startpoint_buffer: Option<&'a mut TimePoint> = None;
        let mut endpoint_buffer: Option<&'a mut TimePoint> = None;

        // the extra block satisfies the borrow checker
        let timings: Vec<_> = {
            let filter_map_closure = |part: &'a mut SsaFilePart| -> Option<(&'a mut TimePoint, &'a mut TimePoint, &'a mut String)> {
                use self::SsaFilePart::*;
                match *part {
                    TimespanStart(ref mut start) => {
                        assert_eq!(startpoint_buffer, None); // parser should have ensured that no two consecutive SSA start times exist
                        startpoint_buffer = Some(start);
                        None
                    }
                    TimespanEnd(ref mut end) => {
                        assert_eq!(endpoint_buffer, None); // parser should have ensured that no two consecutive SSA end times exist
                        endpoint_buffer = Some(end);
                        None
                    }
                    Text(ref mut text) => {
                        // reset the timepoint buffers
                        let snatched_startpoint_buffer = startpoint_buffer.take();
                        let snatched_endpoint_buffer = endpoint_buffer.take();

                        let start = snatched_startpoint_buffer.expect("SSA parser should have ensured that every line has a startpoint");
                        let end = snatched_endpoint_buffer.expect("SSA parser should have ensured that every line has a endpoint");

                        Some((start, end, text))
                    }
                    Filler(_) => None,
                }
            };

            self.v.iter_mut().filter_map(filter_map_closure).collect()
        };

        // every timespan should now consist of a beginning and a end (this should be ensured by parser)
        assert_eq!(startpoint_buffer, None);
        assert_eq!(endpoint_buffer, None);

        timings
    }
}

impl SubtitleFileInterface for SsaFile {
    fn get_subtitle_entries(&self) -> SubtitleParserResult<Vec<SubtitleEntry>> {
        // it's unfortunate we have to clone the file before using
        // `get_subtitle_entries_mut()`, but otherwise we'd have to copy the`
        // `get_subtitle_entries_mut()` and create a non-mut-reference version
        // of it (much code duplication); I think a `clone` in this
        // not-time-critical code is acceptable, and after HKT become
        // available, this can be solved much nicer.
        let mut new_file = self.clone();
        let timings = new_file
            .get_subtitle_entries_mut()
            .into_iter()
            .map(|(&mut start, &mut end, text)| SubtitleEntry::new(TimeSpan::new(start, end), text.clone()))
            .collect();

        Ok(timings)
    }

    fn update_subtitle_entries(&mut self, new_subtitle_entries: &[SubtitleEntry]) -> SubtitleParserResult<()> {
        let subtitle_entries = self.get_subtitle_entries_mut();
        assert_eq!(subtitle_entries.len(), new_subtitle_entries.len()); // required by specification of this function

        for ((start_ref, end_ref, text_ref), new_entry_ref) in subtitle_entries.into_iter().zip(new_subtitle_entries) {
            *start_ref = new_entry_ref.timespan.start;
            *end_ref = new_entry_ref.timespan.end;
            if let Some(ref text) = new_entry_ref.line {
                *text_ref = text.clone();
            }
        }

        Ok(())
    }

    fn to_data(&self) -> SubtitleParserResult<Vec<u8>> {
        // timing to string like "0:00:22.21"
        let fn_timing_to_string = |t: TimePoint| {
            let p = if t.msecs() < 0 { -t } else { t };
            format!(
                "{}{}:{:02}:{:02}.{:02}",
                if t.msecs() < 0 { "-" } else { "" },
                p.hours(),
                p.mins_comp(),
                p.secs_comp(),
                p.csecs_comp()
            )
        };

        let fn_file_part_to_string = |part: &SsaFilePart| {
            use self::SsaFilePart::*;
            match *part {
                Filler(ref t) | Text(ref t) => t.clone(),
                TimespanStart(start) => fn_timing_to_string(start),
                TimespanEnd(end) => fn_timing_to_string(end),
            }
        };

        let result: String = self.v.iter().map(fn_file_part_to_string).collect();

        Ok(result.into_bytes())
    }
}