duster/src/renderer/renderer.rs

use crate::parser::template;
use crate::parser::Body;
use crate::parser::DustTag;
use crate::parser::KVPair;
use crate::parser::RValue;
use crate::parser::Special;
use crate::parser::Template;
use crate::parser::TemplateElement;
use crate::renderer::context_element::ContextElement;
use crate::renderer::errors::CompileError;
use crate::renderer::errors::RenderError;
use crate::renderer::errors::WalkError;
use crate::renderer::inline_partial_tree::extract_inline_partials;
use crate::renderer::inline_partial_tree::InlinePartialTreeElement;
use crate::renderer::parameters_context::ParametersContext;
use crate::renderer::walking::walk_path;
use std::collections::HashMap;

#[derive(Clone, Debug)]
pub struct CompiledTemplate<'a> {
    template: Template<'a>,
    pub name: String,
}

#[derive(Clone, Debug)]
pub struct DustRenderer<'a> {
    templates: HashMap<String, &'a Template<'a>>,
}

pub fn compile_template<'a>(
    source: &'a str,
    name: String,
) -> Result<CompiledTemplate<'a>, CompileError> {
    // TODO: Make this all consuming
    // TODO: This could use better error management
    let (_remaining, parsed_template) = template(source).expect("Failed to compile template");
    Ok(CompiledTemplate {
        template: parsed_template,
        name: name,
    })
}

impl<'a> DustRenderer<'a> {
    pub fn new() -> DustRenderer<'a> {
        DustRenderer {
            templates: HashMap::new(),
        }
    }

    pub fn load_source(&mut self, template: &'a CompiledTemplate) {
        self.templates
            .insert(template.name.clone(), &template.template);
    }

    pub fn render(
        &'a self,
        name: &str,
        breadcrumbs: &Vec<&'a dyn ContextElement>,
    ) -> Result<String, RenderError> {
        self.render_template(name, breadcrumbs, None)
    }

    fn render_template(
        &'a self,
        name: &str,
        breadcrumbs: &Vec<&'a dyn ContextElement>,
        blocks: Option<&'a InlinePartialTreeElement<'a>>,
    ) -> Result<String, RenderError> {
        let main_template = match self.templates.get(name) {
            Some(tmpl) => tmpl,
            None => {
                return Err(RenderError::TemplateNotFound(name.to_owned()));
            }
        };
        let extracted_inline_partials = extract_inline_partials(main_template);
        let new_blocks = InlinePartialTreeElement::new(blocks, extracted_inline_partials);
        self.render_body(&main_template.contents, breadcrumbs, &new_blocks)
    }

    fn render_body(
        &'a self,
        body: &'a Body,
        breadcrumbs: &Vec<&'a dyn ContextElement>,
        blocks: &'a InlinePartialTreeElement<'a>,
    ) -> Result<String, RenderError> {
        let mut output = String::new();
        for elem in &body.elements {
            match elem {
                TemplateElement::TEIgnoredWhitespace(_) => {}
                TemplateElement::TESpan(span) => output.push_str(span.contents),
                TemplateElement::TETag(dt) => {
                    output.push_str(&self.render_tag(dt, breadcrumbs, blocks)?);
                }
            }
        }
        Ok(output)
    }

    fn render_tag(
        &'a self,
        tag: &'a DustTag,
        breadcrumbs: &Vec<&'a dyn ContextElement>,
        blocks: &'a InlinePartialTreeElement<'a>,
    ) -> Result<String, RenderError> {
        match tag {
            DustTag::DTComment(_comment) => (),
            DustTag::DTSpecial(special) => {
                return Ok(match special {
                    Special::Space => " ",
                    Special::NewLine => "\n",
                    Special::CarriageReturn => "\r",
                    Special::LeftCurlyBrace => "{",
                    Special::RightCurlyBrace => "}",
                }
                .to_owned())
            }
            DustTag::DTReference(reference) => {
                let val = walk_path(breadcrumbs, &reference.path.keys);
                match val {
                    Err(WalkError::CantWalk) => return Ok("".to_owned()),
                    Ok(final_val) => {
                        let loop_elements = final_val.get_loop_elements();
                        if loop_elements.is_empty() {
                            return Ok("".to_owned());
                        } else {
                            return final_val.render(&reference.filters);
                        }
                    }
                }
            }
            DustTag::DTSection(container) => {
                let val = walk_path(breadcrumbs, &container.path.keys);
                let loop_elements: Vec<&dyn ContextElement> = self.get_loop_elements(val);
                if loop_elements.is_empty() {
                    // Oddly enough if the value is falsey (like
                    // an empty array or null), Dust uses the
                    // original context before walking the path as
                    // the context for rendering the else block
                    return match &container.else_contents {
                        Some(body) => self.render_body(&body, breadcrumbs, blocks),
                        None => Ok("".to_owned()),
                    };
                } else {
                    match &container.contents {
                        None => return Ok("".to_owned()),
                        Some(body) => {
                            let rendered_results: Result<Vec<String>, RenderError> = loop_elements
                                .into_iter()
                                .map(|array_elem| {
                                    let mut new_breadcumbs = breadcrumbs.clone();
                                    new_breadcumbs.push(array_elem);
                                    self.render_body(&body, &new_breadcumbs, blocks)
                                })
                                .collect();
                            let rendered_slice: &[String] = &rendered_results?;
                            return Ok(rendered_slice.join(""));
                        }
                    }
                }
            }
            DustTag::DTExists(container) => {
                let val = walk_path(breadcrumbs, &container.path.keys);
                let loop_elements: Vec<&dyn ContextElement> = self.get_loop_elements(val);
                if loop_elements.is_empty() {
                    return match &container.else_contents {
                        Some(body) => self.render_body(&body, breadcrumbs, blocks),
                        None => Ok("".to_owned()),
                    };
                } else {
                    return match &container.contents {
                        None => Ok("".to_owned()),
                        Some(body) => self.render_body(&body, breadcrumbs, blocks),
                    };
                }
            }
            DustTag::DTNotExists(container) => {
                let val = walk_path(breadcrumbs, &container.path.keys);
                let loop_elements: Vec<&dyn ContextElement> = self.get_loop_elements(val);
                if !loop_elements.is_empty() {
                    return match &container.else_contents {
                        Some(body) => self.render_body(&body, breadcrumbs, blocks),
                        None => Ok("".to_owned()),
                    };
                } else {
                    return match &container.contents {
                        None => Ok("".to_owned()),
                        Some(body) => self.render_body(&body, breadcrumbs, blocks),
                    };
                }
            }
            DustTag::DTPartial(partial) => {
                if partial.params.is_empty() {
                    let rendered_content =
                        self.render_template(&partial.name, breadcrumbs, Some(blocks))?;
                    return Ok(rendered_content);
                } else {
                    let injected_context = ParametersContext::new(breadcrumbs, &partial.params);
                    let mut new_breadcrumbs = breadcrumbs.clone();
                    new_breadcrumbs.insert(new_breadcrumbs.len() - 1, &injected_context);
                    let rendered_content =
                        self.render_template(&partial.name, &new_breadcrumbs, Some(blocks))?;
                    return Ok(rendered_content);
                }
            }
            DustTag::DTInlinePartial(named_block) => {
                // Inline partials are blank during rendering (they get injected into blocks)
                return Ok("".to_owned());
            }
            DustTag::DTBlock(named_block) => {
                match blocks.get_block(named_block.name) {
                    None => match &named_block.contents {
                        None => return Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            return Ok(rendered_content);
                        }
                    },
                    Some(interior) => match interior {
                        None => return Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            return Ok(rendered_content);
                        }
                    },
                };
            }
            DustTag::DTHelperEquals(parameterized_block) => {
                let param_map: HashMap<&str, &RValue<'a>> = parameterized_block
                    .params
                    .iter()
                    .map(|pair: &KVPair<'a>| (pair.key, &pair.value))
                    .collect();
                // Special case: when comparing two RVPaths, if the
                // path is equal then dust assumes the values are
                // equal (otherwise, non-scalar values are
                // automatically not equal)
                if Self::are_paths_identical(&param_map) {
                    return match &parameterized_block.contents {
                        None => Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            Ok(rendered_content)
                        }
                    };
                }

                let left_side: Result<&dyn ContextElement, WalkError> = match param_map.get("key") {
                    None => return Ok("".to_owned()),
                    Some(rval) => match rval {
                        RValue::RVString(text) => Ok(text),
                        RValue::RVPath(path) => walk_path(breadcrumbs, &path.keys),
                        RValue::RVPositiveInteger(num) => Ok(num),
                    },
                };
                let right_side: Result<&dyn ContextElement, WalkError> =
                    match param_map.get("value") {
                        None => Err(WalkError::CantWalk),
                        Some(rval) => match rval {
                            RValue::RVString(text) => Ok(text),
                            RValue::RVPath(path) => walk_path(breadcrumbs, &path.keys),
                            RValue::RVPositiveInteger(num) => Ok(num),
                        },
                    };
                if left_side == right_side {
                    match &parameterized_block.contents {
                        None => return Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            return Ok(rendered_content);
                        }
                    }
                } else {
                    match &parameterized_block.else_contents {
                        None => return Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            return Ok(rendered_content);
                        }
                    }
                }
            }
            DustTag::DTHelperNotEquals(parameterized_block) => {
                let param_map: HashMap<&str, &RValue<'a>> = parameterized_block
                    .params
                    .iter()
                    .map(|pair: &KVPair<'a>| (pair.key, &pair.value))
                    .collect();
                // Special case: when comparing two RVPaths, if the
                // path is equal then dust assumes the values are
                // equal (otherwise, non-scalar values are
                // automatically not equal)
                if Self::are_paths_identical(&param_map) {
                    return match &parameterized_block.else_contents {
                        None => Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            Ok(rendered_content)
                        }
                    };
                }

                let left_side: Result<&dyn ContextElement, WalkError> = match param_map.get("key") {
                    None => return Ok("".to_owned()),
                    Some(rval) => match rval {
                        RValue::RVString(text) => Ok(text),
                        RValue::RVPath(path) => walk_path(breadcrumbs, &path.keys),
                        RValue::RVPositiveInteger(num) => Ok(num),
                    },
                };
                let right_side: Result<&dyn ContextElement, WalkError> =
                    match param_map.get("value") {
                        None => Err(WalkError::CantWalk),
                        Some(rval) => match rval {
                            RValue::RVString(text) => Ok(text),
                            RValue::RVPath(path) => walk_path(breadcrumbs, &path.keys),
                            RValue::RVPositiveInteger(num) => Ok(num),
                        },
                    };
                if left_side != right_side {
                    match &parameterized_block.contents {
                        None => return Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            return Ok(rendered_content);
                        }
                    }
                } else {
                    match &parameterized_block.else_contents {
                        None => return Ok("".to_owned()),
                        Some(body) => {
                            let rendered_content = self.render_body(body, breadcrumbs, blocks)?;
                            return Ok(rendered_content);
                        }
                    }
                }
            }
            _ => (), // TODO: Implement the rest
        }
        Ok("".to_owned())
    }

    /// Gets the elements to loop over for a section.
    ///
    /// If the value is falsey, and therefore should render the else
    /// block, this will return an empty vector.
    fn get_loop_elements<'b>(
        &'a self,
        walk_result: Result<&'b dyn ContextElement, WalkError>,
    ) -> Vec<&'b dyn ContextElement> {
        match walk_result {
            Err(WalkError::CantWalk) => Vec::new(),
            Ok(walk_target) => walk_target.get_loop_elements(),
        }
    }

    fn are_paths_identical<'b>(param_map: &HashMap<&str, &RValue<'b>>) -> bool {
        match (param_map.get("key"), param_map.get("value")) {
            (None, _) => false,
            (_, None) => false,
            (Some(key_rval), Some(value_rval)) => match (key_rval, value_rval) {
                (RValue::RVPath(key_path), RValue::RVPath(value_path)) => {
                    key_path.keys == value_path.keys
                }
                _ => false,
            },
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::parser::Filter;
    use crate::renderer::context_element::Loopable;
    use crate::renderer::context_element::Renderable;
    use crate::renderer::context_element::Walkable;
    use crate::renderer::CompareContextElement;

    impl<I: 'static + ContextElement + Clone> ContextElement for HashMap<String, I> {}

    impl<I: ContextElement> Renderable for HashMap<String, I> {
        fn render(&self, _filters: &Vec<Filter>) -> Result<String, RenderError> {
            // TODO: handle the filters
            Ok("[object Object]".to_owned())
        }
    }

    impl<I: ContextElement> Walkable for HashMap<String, I> {
        fn walk(&self, segment: &str) -> Result<&dyn ContextElement, WalkError> {
            let child = self.get(segment).ok_or(WalkError::CantWalk)?;
            Ok(child)
        }
    }

    impl<I: 'static + ContextElement + Clone> Loopable for HashMap<String, I> {
        fn get_loop_elements(&self) -> Vec<&dyn ContextElement> {
            vec![self]
        }
    }

    impl<I: 'static + ContextElement + Clone> CompareContextElement for HashMap<String, I> {
        fn equals(&self, other: &dyn ContextElement) -> bool {
            false
        }
    }

    #[test]
    fn test_walk_path() {
        let context: HashMap<String, String> = [
            ("cat".to_string(), "kitty".to_string()),
            ("dog".to_string(), "doggy".to_string()),
            ("tiger".to_string(), "murderkitty".to_string()),
        ]
        .iter()
        .cloned()
        .collect();
        let number_context: HashMap<String, u64> = [
            ("cat".to_string(), 1),
            ("dog".to_string(), 2),
            ("tiger".to_string(), 3),
        ]
        .iter()
        .cloned()
        .collect();
        let deep_context: HashMap<String, HashMap<String, String>> = [
            (
                "cat".to_string(),
                [("food".to_string(), "meat".to_string())]
                    .iter()
                    .cloned()
                    .collect(),
            ),
            (
                "dog".to_string(),
                [("food".to_string(), "meat".to_string())]
                    .iter()
                    .cloned()
                    .collect(),
            ),
            (
                "tiger".to_string(),
                [("food".to_string(), "people".to_string())]
                    .iter()
                    .cloned()
                    .collect(),
            ),
        ]
        .iter()
        .cloned()
        .collect();

        assert_eq!(
            walk_path(&vec![&context as &dyn ContextElement], &vec!["cat"])
                .unwrap()
                .render(&Vec::new())
                .unwrap(),
            "kitty".to_owned()
        );
        assert_eq!(
            walk_path(
                &vec![&number_context as &dyn ContextElement],
                &vec!["tiger"]
            )
            .unwrap()
            .render(&Vec::new())
            .unwrap(),
            "3".to_owned()
        );
        assert_eq!(
            walk_path(
                &vec![&deep_context as &dyn ContextElement],
                &vec!["tiger", "food"]
            )
            .unwrap()
            .render(&Vec::new())
            .unwrap(),
            "people".to_owned()
        );
    }
}