remove treehouse-format crate and collapse everything into src

src/tree/mini_template.rs

@@ -0,0 +1,224 @@
+//! Minimalistic templating engine that integrates with the .tree format and Markdown.
+//!
+//! Mostly to avoid pulling in Handlebars everywhere; mini_template, unlike Handlebars, also allows
+//! for injecting *custom, stateful* context into the renderer, which is important for things like
+//! the `pic` template to work.
+
+use std::fmt::Write;
+use std::ops::Range;
+
+use crate::{
+    config::Config,
+    dirs::Dirs,
+    html::EscapeHtml,
+    state::Treehouse,
+    vfs::{self, Content, VPath},
+};
+
+struct Lexer<'a> {
+    input: &'a str,
+    position: usize,
+
+    // Despite this parser's intentional simplicity, a peekahead buffer needs to be used for
+    // performance because tokens are usually quite long and therefore reparsing them would be
+    // too expensive.
+    peek_buffer: Option<(Token, usize)>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum TokenKind {
+    /// Verbatim text, may be inside of a template.
+    Text,
+    Open(EscapingMode), // {%
+    Close,              // %}
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum EscapingMode {
+    EscapeHtml,
+    NoEscaping,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Token {
+    kind: TokenKind,
+    range: Range<usize>,
+}
+
+impl<'a> Lexer<'a> {
+    fn new(input: &'a str) -> Self {
+        Self {
+            input,
+            position: 0,
+            peek_buffer: None,
+        }
+    }
+
+    fn current(&self) -> Option<char> {
+        self.input[self.position..].chars().next()
+    }
+
+    fn advance(&mut self) {
+        self.position += self.current().map(|c| c.len_utf8()).unwrap_or(0);
+    }
+
+    fn create_token(&self, start: usize, kind: TokenKind) -> Token {
+        Token {
+            kind,
+            range: start..self.position,
+        }
+    }
+
+    fn next_inner(&mut self) -> Option<Token> {
+        if let Some((token, after_token)) = self.peek_buffer.take() {
+            self.position = after_token;
+            return Some(token);
+        }
+
+        let start = self.position;
+        match self.current() {
+            Some('{') => {
+                self.advance();
+                if self.current() == Some('%') {
+                    self.advance();
+                    if self.current() == Some('!') {
+                        Some(self.create_token(start, TokenKind::Open(EscapingMode::NoEscaping)))
+                    } else {
+                        Some(self.create_token(start, TokenKind::Open(EscapingMode::EscapeHtml)))
+                    }
+                } else {
+                    self.advance();
+                    Some(self.create_token(start, TokenKind::Text))
+                }
+            }
+            Some('%') => {
+                self.advance();
+                if self.current() == Some('}') {
+                    self.advance();
+                    Some(self.create_token(start, TokenKind::Close))
+                } else {
+                    self.advance();
+                    Some(self.create_token(start, TokenKind::Text))
+                }
+            }
+            Some(_) => {
+                while !matches!(self.current(), Some('{' | '%') | None) {
+                    self.advance();
+                }
+                Some(self.create_token(start, TokenKind::Text))
+            }
+            None => None,
+        }
+    }
+
+    fn peek_inner(&mut self) -> Option<Token> {
+        let position = self.position;
+        let token = self.next();
+        let after_token = self.position;
+        self.position = position;
+
+        if let Some(token) = token.clone() {
+            self.peek_buffer = Some((token, after_token));
+        }
+
+        token
+    }
+
+    fn next(&mut self) -> Option<Token> {
+        self.next_inner().map(|mut token| {
+            // Coalesce multiple Text tokens into one.
+            if token.kind == TokenKind::Text {
+                while let Some(Token {
+                    kind: TokenKind::Text,
+                    ..
+                }) = self.peek_inner()
+                {
+                    let next_token = self.next_inner().unwrap();
+                    token.range.end = next_token.range.end;
+                }
+            }
+            token
+        })
+    }
+}
+
+struct Renderer<'a> {
+    lexer: Lexer<'a>,
+    output: String,
+}
+
+struct InvalidTemplate;
+
+impl Renderer<'_> {
+    fn emit_token_verbatim(&mut self, token: &Token) {
+        self.output.push_str(&self.lexer.input[token.range.clone()]);
+    }
+
+    fn render(&mut self, config: &Config, treehouse: &Treehouse, dirs: &Dirs) {
+        let kind_of = |token: &Token| token.kind;
+
+        while let Some(token) = self.lexer.next() {
+            match token.kind {
+                TokenKind::Open(escaping) => {
+                    let inside = self.lexer.next();
+                    let close = self.lexer.next();
+
+                    if let Some((TokenKind::Text, TokenKind::Close)) = inside
+                        .as_ref()
+                        .map(kind_of)
+                        .zip(close.as_ref().map(kind_of))
+                    {
+                        match Self::render_template(
+                            config,
+                            treehouse,
+                            dirs,
+                            self.lexer.input[inside.as_ref().unwrap().range.clone()].trim(),
+                        ) {
+                            Ok(s) => match escaping {
+                                EscapingMode::EscapeHtml => {
+                                    _ = write!(self.output, "{}", EscapeHtml(&s));
+                                }
+                                EscapingMode::NoEscaping => self.output.push_str(&s),
+                            },
+                            Err(InvalidTemplate) => {
+                                inside.inspect(|token| self.emit_token_verbatim(token));
+                                close.inspect(|token| self.emit_token_verbatim(token));
+                            }
+                        }
+                    } else {
+                        inside.inspect(|token| self.emit_token_verbatim(token));
+                        close.inspect(|token| self.emit_token_verbatim(token));
+                    }
+                }
+                _ => self.emit_token_verbatim(&token),
+            }
+        }
+    }
+
+    fn render_template(
+        config: &Config,
+        _treehouse: &Treehouse,
+        dirs: &Dirs,
+        template: &str,
+    ) -> Result<String, InvalidTemplate> {
+        let (function, arguments) = template.split_once(' ').unwrap_or((template, ""));
+        match function {
+            "pic" => Ok(config.pic_url(&*dirs.pic, arguments)),
+            "include_static" => VPath::try_new(arguments)
+                .ok()
+                .and_then(|vpath| vfs::query::<Content>(&dirs.static_, vpath))
+                .and_then(|c| c.string().ok())
+                .ok_or(InvalidTemplate),
+            _ => Err(InvalidTemplate),
+        }
+    }
+}
+
+pub fn render(config: &Config, treehouse: &Treehouse, dirs: &Dirs, input: &str) -> String {
+    let mut renderer = Renderer {
+        lexer: Lexer::new(input),
+        output: String::new(),
+    };
+    renderer.render(config, treehouse, dirs);
+    renderer.output
+}