diff2html 0.2.3

Pretty diff to html Rust library (diff2html) https://diff2html.xyz
Documentation
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use std::cmp::{max, min};

use handlebars::Handlebars;
use v_htmlescape::escape;

use super::utils::{self, rematch, Difference};
use crate::{config::Diff2HtmlConfig, parse};

static GENERIC_COLUMN_LINE_NUMBER: &'static str =
    include_str!("../templates/generic-column-line-number.hbs");
static GENERIC_EMPTY_DIFF: &'static str = include_str!("../templates/generic-empty-diff.hbs");
static GENERIC_FILE_PATH: &'static str = include_str!("../templates/generic-file-path.hbs");
static GENERIC_LINE: &'static str = include_str!("../templates/generic-line.hbs");
static GENERIC_WRAPPER: &'static str = include_str!("../templates/generic-wrapper.hbs");
static SIDE_BY_SIDE_FILE_DIFF: &'static str =
    include_str!("../templates/side-by-side-file-diff.hbs");
static ICON_FILE: &'static str = include_str!("../templates/icon-file.hbs");

pub struct SideBySidePrinter {
    config: Diff2HtmlConfig,
    handlebars: Handlebars,
    line_matcher: rematch::Rematcher<parse::Line>,
    diff_matcher: rematch::Rematcher<Difference>,
}

impl SideBySidePrinter {
    pub fn new(config: Diff2HtmlConfig) -> SideBySidePrinter {
        let mut handlebars = Handlebars::new();
        handlebars
            .register_template_string("generic-column-line-number", GENERIC_COLUMN_LINE_NUMBER)
            .unwrap();
        handlebars
            .register_template_string("generic-empty-diff", GENERIC_EMPTY_DIFF)
            .unwrap();
        handlebars
            .register_template_string("generic-file-path", GENERIC_FILE_PATH)
            .unwrap();
        handlebars
            .register_template_string("generic-line", GENERIC_LINE)
            .unwrap();
        handlebars
            .register_template_string("generic-wrapper", GENERIC_WRAPPER)
            .unwrap();
        handlebars
            .register_template_string("side-by-side-file-diff", SIDE_BY_SIDE_FILE_DIFF)
            .unwrap();

        SideBySidePrinter {
            config: config,
            handlebars: handlebars,
            line_matcher: utils::get_line_matcher(),
            diff_matcher: utils::get_difference_matcher(),
        }
    }

    pub fn render(&self, files: &Vec<parse::File>) -> String {
        let output = files
            .iter()
            .map(|file| {
                let diffs = if file.blocks.len() > 0 {
                    self.generate_file_html(file)
                } else {
                    self.generate_empty_diff()
                };
                self.make_file_diff_html(file, diffs)
            })
            .collect::<Vec<String>>()
            .join("\n");

        self.handlebars
            .render(
                "generic-wrapper",
                &json!({
                    "content": output,
                }),
            )
            .unwrap()
    }

    fn make_file_diff_html(&self, file: &parse::File, diffs: SideBySideFile) -> String {
        let file_path = self
            .handlebars
            .render(
                "generic-file-path",
                &json!({
                    "fileDiffName": utils::get_diff_name(file),
                    "fileIcon": ICON_FILE,
                    "fileTag": utils::get_line_type_tag(file).to_owned(),
                }),
            )
            .unwrap();

        self.handlebars
            .render(
                "side-by-side-file-diff",
                &json!({
                    "file": file.to_owned(),
                    "fileHtmlId": utils::get_html_id(file),
                    "diffs": diffs,
                    "filePath": file_path,
                }),
            )
            .unwrap()
    }

    fn generate_file_html(&self, file: &parse::File) -> SideBySideFile {
        let mut file_html = SideBySideFile::new();

        file.blocks.iter().for_each(|block| {
            file_html.left += &utils::make_column_line_number_html(
                &self.handlebars,
                block.header.as_ref().unwrap(),
                "d2h-code-side-linenumber",
                "d2h-code-side-line",
            );
            file_html.right += &utils::make_column_line_number_html(
                &self.handlebars,
                "",
                "d2h-code-side-linenumber",
                "d2h-code-side-line",
            );

            let mut old_lines = Vec::new();
            let mut new_lines = Vec::new();

            for i in 0..block.lines.len() {
                let line = &block.lines[i];
                let prefix = &line.content[0..1];
                let escaped_line = escape(&line.content[1..]).to_string();

                if line.line_type != Some(parse::LineType::Inserts)
                    && (new_lines.len() > 0
                        || (line.line_type != Some(parse::LineType::Deletes)
                            && old_lines.len() > 0))
                {
                    self.process_change_block(file, &mut file_html, &mut old_lines, &mut new_lines);
                }

                if line.line_type == Some(parse::LineType::Context) {
                    file_html.left += &self.generate_line_html(
                        file.is_combined,
                        &line.line_type.as_ref().unwrap(),
                        line.old_number,
                        escaped_line.to_owned(),
                        Some(prefix),
                    );
                    file_html.right += &self.generate_line_html(
                        file.is_combined,
                        &line.line_type.as_ref().unwrap(),
                        line.new_number,
                        escaped_line.to_owned(),
                        Some(prefix),
                    );
                } else if line.line_type == Some(parse::LineType::Inserts) && old_lines.len() == 0 {
                    file_html.left += &self.generate_line_html(
                        file.is_combined,
                        &parse::LineType::Context,
                        None,
                        "".to_owned(),
                        None,
                    );
                    file_html.right += &self.generate_line_html(
                        file.is_combined,
                        &line.line_type.as_ref().unwrap(),
                        line.new_number,
                        escaped_line.to_owned(),
                        Some(prefix),
                    );
                } else if line.line_type == Some(parse::LineType::Deletes) {
                    old_lines.push(line.to_owned());
                } else if line.line_type == Some(parse::LineType::Inserts) && old_lines.len() > 0 {
                    new_lines.push(line.to_owned());
                } else {
                    eprintln!("Unknown state in html side-by-side generator.");
                    self.process_change_block(file, &mut file_html, &mut old_lines, &mut new_lines);
                }
            }

            self.process_change_block(file, &mut file_html, &mut old_lines, &mut new_lines);
        });

        file_html
    }

    fn process_change_block(
        &self,
        file: &parse::File,
        file_html: &mut SideBySideFile,
        old_lines: &mut Vec<parse::Line>,
        new_lines: &mut Vec<parse::Line>,
    ) {
        let comparisons = old_lines.len() * new_lines.len();
        let max_comparisons = 2500;
        let do_matching = comparisons < max_comparisons && (self.config.matching != "none");

        let old_lines2 = old_lines.to_owned();
        let new_lines2 = new_lines.to_owned();
        let (matches, insert_type, delete_type) = {
            if do_matching {
                (
                    self.line_matcher.matches(&old_lines2, &new_lines2),
                    parse::LineType::InsertChanges,
                    parse::LineType::DeleteChanges,
                )
            } else {
                (
                    vec![vec![old_lines2.as_ref(), new_lines2.as_ref()]],
                    parse::LineType::Inserts,
                    parse::LineType::Deletes,
                )
            }
        };

        matches.iter().for_each(|item| {
            *old_lines = item[0].to_vec();
            *new_lines = item[1].to_vec();

            let common = min(old_lines.len(), new_lines.len());
            let max = max(old_lines.len(), new_lines.len());

            let mut j = 0;
            let mut old_line;
            let mut new_line;
            while j < common {
                old_line = Some(&old_lines[j]);
                new_line = Some(&new_lines[j]);

                let diff = utils::diff_highlight(
                    &self.config,
                    Some(&self.diff_matcher),
                    &old_line.as_ref().unwrap().content,
                    &new_line.as_ref().unwrap().content,
                );

                file_html.left += &self.generate_line_html(
                    file.is_combined,
                    &delete_type,
                    old_line.as_ref().and_then(|v| v.old_number),
                    diff.first.line,
                    Some(diff.first.prefix),
                );
                file_html.right += &self.generate_line_html(
                    file.is_combined,
                    &insert_type,
                    new_line.as_ref().and_then(|v| v.new_number),
                    diff.second.line,
                    Some(diff.second.prefix),
                );

                j += 1;
            }

            if max > common {
                let old_slice = &old_lines[common..];
                let new_slice = &new_lines[common..];

                let html = self.process_lines(file.is_combined, &old_slice, &new_slice);
                file_html.left += &html.left;
                file_html.right += &html.right;
            }
        });

        *old_lines = Vec::new();
        *new_lines = Vec::new();
    }

    fn process_lines(
        &self,
        is_combined: bool,
        old_lines: &[parse::Line],
        new_lines: &[parse::Line],
    ) -> SideBySideFile {
        let mut file_html = SideBySideFile::new();

        let max_lines_number = max(old_lines.len(), new_lines.len());

        for i in 0..max_lines_number {
            let old_line = old_lines.get(i);
            let new_line = new_lines.get(i);
            let mut old_content = None;
            let mut new_content = None;
            let mut old_prefix = None;
            let mut new_prefix = None;

            if let Some(old_line) = old_line {
                old_content = Some(escape(&old_line.content[1..]).to_string());
                old_prefix = Some(&old_line.content[0..1])
            }

            if let Some(new_line) = new_line {
                new_content = Some(escape(&new_line.content[1..]).to_string());
                new_prefix = Some(&new_line.content[0..1])
            }

            if old_line.is_some() && new_line.is_some() {
                file_html.left += &self.generate_line_html(
                    is_combined,
                    old_line.as_ref().unwrap().line_type.as_ref().unwrap(),
                    old_line.as_ref().unwrap().old_number,
                    old_content.unwrap(),
                    old_prefix,
                );
                file_html.right += &self.generate_line_html(
                    is_combined,
                    new_line.as_ref().unwrap().line_type.as_ref().unwrap(),
                    new_line.as_ref().unwrap().old_number,
                    new_content.unwrap(),
                    new_prefix,
                );
            } else if old_line.is_some() {
                file_html.left += &self.generate_line_html(
                    is_combined,
                    old_line.as_ref().unwrap().line_type.as_ref().unwrap(),
                    old_line.as_ref().unwrap().old_number,
                    old_content.unwrap(),
                    old_prefix,
                );
                file_html.right += &self.generate_line_html(
                    is_combined,
                    &parse::LineType::Context,
                    None,
                    "".to_owned(),
                    None,
                );
            } else if new_line.is_some() {
                file_html.left += &self.generate_line_html(
                    is_combined,
                    &parse::LineType::Context,
                    None,
                    "".to_owned(),
                    None,
                );
                file_html.right += &self.generate_line_html(
                    is_combined,
                    new_line.as_ref().unwrap().line_type.as_ref().unwrap(),
                    new_line.as_ref().unwrap().new_number,
                    new_content.unwrap(),
                    new_prefix,
                );
            } else {
                eprintln!("Unknown path.");
            }
        }

        file_html
    }

    fn generate_line_html(
        &self,
        is_combined: bool,
        line_type: &parse::LineType,
        number: Option<usize>,
        content: String,
        possible_prefix: Option<&str>,
    ) -> String {
        let mut line_class = "d2h-code-side-linenumber".to_owned();
        let mut content_class = "d2h-code-side-line".to_owned();
        let mut line_type = utils::get_line_type_class(line_type).to_owned();

        if number.is_none() && content == "" {
            line_class += " d2h-code-side-emptyplaceholder";
            content_class += " d2h-code-side-emptyplaceholder";
            line_type += " d2h-emptyplaceholder";
        }

        let (prefix, line_without_prefix) = match possible_prefix {
            Some(prefix) => (prefix, content),
            _ => {
                let line_with_prefix = utils::separate_prefix(is_combined, &content);
                (line_with_prefix.prefix, line_with_prefix.line.to_owned())
            }
        };

        self.handlebars
            .render(
                "generic-line",
                &json!({
                    "type": line_type,
                    "lineClass": line_class,
                    "contentClass": content_class,
                    "prefix": prefix.to_owned(),
                    "content": line_without_prefix,
                    "lineNumber": number,
                }),
            )
            .unwrap()
    }

    fn generate_empty_diff(&self) -> SideBySideFile {
        let mut file_html = SideBySideFile::new();
        file_html.left += &utils::generate_empty_diff(&self.handlebars, "d2h-code-line");
        file_html
    }
}

#[derive(Debug, Serialize)]
pub struct SideBySideFile {
    pub left: String,
    pub right: String,
}

impl SideBySideFile {
    fn new() -> SideBySideFile {
        SideBySideFile {
            left: String::new(),
            right: String::new(),
        }
    }
}