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
 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
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160

//! Utilities for quickly building a source tree from a series of templates.

use serde::Serialize;
use std::fs::{create_dir_all, File};
use std::io::Write;
use std::path::Path;
use tinytemplate::TinyTemplate;

use crate::spec::Spec;

/// Represents the contents of a source file that needs to be generated.
pub enum SourceFileContents {
    /// Represents a template. The template will be invoked with the spec
    /// contained in `Polyhorn.toml`.
    Template(&'static str),

    /// Copies the contents of a file from the given slice without any string
    /// interpolation.
    Copy(&'static [u8]),
}

/// A single source file that is generated.
pub struct SourceFile {
    name: String,
    contents: SourceFileContents,
}

/// A source tree that is used to queue files that need to be generated.
pub struct SourceTree {
    files: Vec<SourceFile>,
}

/// Context that is passed to the template engine that is used for generating
/// source files dynamically.
#[derive(Serialize)]
pub struct Context<'a> {
    spec: &'a Spec,
}

/// An iterator over the files that a source tree generates one-by-one.
pub struct SourceTreeIter<'a> {
    files: &'a [SourceFile],
    current: usize,
    context: Context<'a>,
    destination_path: &'a Path,
}

/// Represents an error that occurs during source tree generation.
#[derive(Debug)]
pub enum Error {
    /// Contains an error returned by the template engine invocation.
    Template(tinytemplate::error::Error),

    /// Contains an IO error that is encountered when writing the generated
    /// source files to disk.
    IO(std::io::Error),
}

impl<'a> Iterator for SourceTreeIter<'a> {
    type Item = Result<(), Error>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.current == self.files.len() {
            return None;
        }

        let file = &self.files[self.current];
        self.current += 1;

        let mut buf = self.destination_path.to_path_buf();
        buf.push(file.name.to_owned());

        {
            let mut buf = buf.clone();
            buf.pop();

            let _ = create_dir_all(buf);
        }

        match file.contents {
            SourceFileContents::Copy(contents) => {
                let mut file = match File::create(buf) {
                    Ok(file) => file,
                    Err(error) => return Some(Err(Error::IO(error))),
                };

                if let Err(error) = file.write_all(contents) {
                    return Some(Err(Error::IO(error)));
                }
            }
            SourceFileContents::Template(template) => {
                let mut engine = TinyTemplate::new();

                if let Err(error) = engine.add_template("template", template) {
                    return Some(Err(Error::Template(error)));
                }

                let contents = match engine.render("template", &self.context) {
                    Ok(contents) => contents,
                    Err(error) => return Some(Err(Error::Template(error))),
                };

                let mut file = match File::create(buf) {
                    Ok(file) => file,
                    Err(error) => return Some(Err(Error::IO(error))),
                };

                if let Err(error) = file.write_all(contents.as_bytes()) {
                    return Some(Err(Error::IO(error)));
                }
            }
        }

        Some(Ok(()))
    }
}

impl SourceTree {
    /// Creates a new empty source tree that can be written to disk.
    pub fn new() -> SourceTree {
        SourceTree { files: vec![] }
    }

    /// Queues a copy of the given contents to a file with the given name.
    pub fn copy(&mut self, name: &str, contents: &'static [u8]) {
        self.files.push(SourceFile {
            name: name.to_owned(),
            contents: SourceFileContents::Copy(contents),
        })
    }

    /// Queues an invocation of the given template that writes the result to a
    /// file with the given name.
    pub fn template(&mut self, name: &str, contents: &'static str) {
        self.files.push(SourceFile {
            name: name.to_owned(),
            contents: SourceFileContents::Template(contents),
        });
    }

    /// Returns the number of files that are queued for generation.
    pub fn len(&self) -> usize {
        self.files.len()
    }

    /// Returns an iterator that generates the source files of this source tree
    /// and writes them to the given destination path one-by-one.
    pub fn generate<'a>(
        &'a self,
        spec: &'a Spec,
        destination_path: &'a Path,
    ) -> SourceTreeIter<'a> {
        SourceTreeIter {
            files: &self.files,
            current: 0,
            context: Context { spec },
            destination_path,
        }
    }
}