duster/src/bin.rs

extern crate nom;

use crate::renderer::CompareContextElement;
use parser::Filter;
use renderer::compile_template;
use renderer::CompiledTemplate;
use renderer::ContextElement;
use renderer::DustRenderer;
use renderer::Loopable;
use renderer::RenderError;
use renderer::Renderable;
use renderer::WalkError;
use renderer::Walkable;
use std::cmp::Ordering;
use std::env;
use std::fs;
use std::io::{self, Read};
use std::path::Path;

mod parser;
mod renderer;

fn main() {
    let context = read_context_from_stdin();

    let argv: Vec<String> = env::args().collect();
    if argv.len() < 2 {
        panic!("Need to pass templates");
    }
    let template_paths = &argv[1..];
    let template_contents: Vec<(String, String)> = template_paths
        .iter()
        .map(|p| {
            let template_content = fs::read_to_string(&p).unwrap();
            (p.to_string(), template_content)
        })
        .collect();
    let compiled_templates: Vec<CompiledTemplate> = template_contents
        .iter()
        .map(|(p, contents)| template_from_file(p, contents))
        .collect();
    let mut dust_renderer = DustRenderer::new();
    compiled_templates.iter().for_each(|template| {
        dust_renderer.load_source(template);
    });
    let main_template_name = &compiled_templates
        .first()
        .expect("There should be more than 1 template")
        .name;
    let breadcrumbs = vec![&context as &dyn ContextElement];
    println!(
        "{}",
        dust_renderer
            .render(main_template_name, &breadcrumbs)
            .expect("Failed to render")
    );
}

fn template_from_file<'a>(file_path: &str, file_contents: &'a str) -> CompiledTemplate<'a> {
    let path: &Path = Path::new(file_path);
    let name = path.file_stem().unwrap();
    compile_template(file_contents, name.to_string_lossy().to_string())
        .expect("Failed to compile template")
}

fn read_context_from_stdin() -> serde_json::Value {
    let mut buffer = String::new();
    io::stdin()
        .read_to_string(&mut buffer)
        .expect("Failed to read stdin");

    serde_json::from_str(&buffer).expect("Failed to parse json")
}

impl ContextElement for serde_json::Value {}

impl Renderable for serde_json::Value {
    fn render(&self, _filters: &Vec<Filter>) -> Result<String, RenderError> {
        match self {
            serde_json::Value::Null => Ok("".to_owned()),
            serde_json::Value::Bool(boolean) => Ok(boolean.to_string()),
            serde_json::Value::Number(num) => Ok(num.to_string()),
            serde_json::Value::String(string) => Ok(string.to_string()),
            serde_json::Value::Array(arr) => {
                // TODO: Handle the filters instead of passing a Vec::new()
                let rendered: Result<Vec<String>, RenderError> =
                    arr.iter().map(|val| val.render(&Vec::new())).collect();
                let rendered_slice: &[String] = &rendered?;
                Ok(rendered_slice.join(","))
            }
            serde_json::Value::Object(_obj) => Ok("[object Object]".to_owned()),
        }
    }
}

impl Walkable for serde_json::Value {
    fn walk(&self, segment: &str) -> Result<&dyn ContextElement, WalkError> {
        match self {
            serde_json::Value::Null => Err(WalkError::CantWalk),
            serde_json::Value::Bool(_boolean) => Err(WalkError::CantWalk),
            serde_json::Value::Number(_num) => Err(WalkError::CantWalk),
            serde_json::Value::String(_string) => Err(WalkError::CantWalk),
            serde_json::Value::Array(_arr) => Err(WalkError::CantWalk),
            serde_json::Value::Object(obj) => obj
                .get(segment)
                .map(|val| val as _)
                .ok_or(WalkError::CantWalk),
        }
    }
}

impl Loopable for serde_json::Value {
    fn get_loop_elements(&self) -> Vec<&dyn ContextElement> {
        match self {
            serde_json::Value::Null => Vec::new(),
            serde_json::Value::Bool(boolean) => {
                if *boolean {
                    vec![self]
                } else {
                    Vec::new()
                }
            }
            serde_json::Value::Number(_num) => vec![self],
            serde_json::Value::String(string_value) => {
                if string_value.is_empty() {
                    Vec::new()
                } else {
                    vec![self]
                }
            }
            serde_json::Value::Array(array_value) => {
                if array_value.is_empty() {
                    Vec::new()
                } else {
                    array_value.iter().map(|x| x as _).collect()
                }
            }
            serde_json::Value::Object(_obj) => vec![self],
        }
    }
}

impl CompareContextElement for serde_json::Value {
    fn equals(&self, other: &dyn ContextElement) -> bool {
        // Handle other serde_json::Value
        match other.to_any().downcast_ref::<Self>() {
            None => (),
            Some(other_json_value) => match (self, other_json_value) {
                // Non-scalar values not caught in the renderer by the
                // identical-path shortcut are always not equal.
                (serde_json::Value::Array(_), _)
                | (_, serde_json::Value::Array(_))
                | (serde_json::Value::Object(_), _)
                | (_, serde_json::Value::Object(_)) => return false,
                _ => return self == other_json_value,
            },
        }
        // Handle string literals
        match other.to_any().downcast_ref::<String>() {
            None => (),
            Some(other_string) => return self.as_str().map_or(false, |s| s == other_string),
        }
        // Handle numeric literals
        match other.to_any().downcast_ref::<u64>() {
            None => (),
            Some(other_num) => return self.as_u64().map_or(false, |n| n == *other_num),
        }
        false
    }

    fn partial_compare(&self, other: &dyn ContextElement) -> Option<Ordering> {
        // Handle other serde_json::Value
        match other.to_any().downcast_ref::<Self>() {
            None => (),
            Some(other_json_value) => {
                return match (self, other_json_value) {
                    (
                        serde_json::Value::Bool(self_boolean),
                        serde_json::Value::Bool(other_boolean),
                    ) => self_boolean.partial_cmp(other_boolean),
                    (
                        serde_json::Value::Number(self_number),
                        serde_json::Value::Number(other_number),
                    ) => match (
                        self_number.as_f64(),
                        other_number.as_f64(),
                        self_number.as_u64(),
                        other_number.as_u64(),
                        self_number.as_i64(),
                        other_number.as_i64(),
                    ) {
                        (_, _, _, _, Some(self_int), Some(other_int)) => {
                            self_int.partial_cmp(&other_int)
                        }
                        (_, _, Some(self_uint), Some(other_uint), _, _) => {
                            self_uint.partial_cmp(&other_uint)
                        }
                        (_, _, Some(_self_uint), _, _, Some(_other_int)) => {
                            // If the previous matches did not catch
                            // it, then other must be negative and
                            // self must be larger than can be
                            // represented with an i64, therefore self
                            // is greater than other.
                            Some(Ordering::Greater)
                        }
                        (_, _, _, Some(_other_uint), Some(_self_int), _) => {
                            // If the previous matches did not catch
                            // it, then self must be negative and
                            // other must be larger than can be
                            // represented with an i64, therefore
                            // other is greater than self.
                            Some(Ordering::Less)
                        }
                        (Some(self_float), Some(other_float), _, _, _, _) => {
                            self_float.partial_cmp(&other_float)
                        }
                        _ => panic!("This should be impossible since u64 and i64 can both be converted to floats"),
                    },
                    (
                        serde_json::Value::String(self_string),
                        serde_json::Value::String(other_string),
                    ) => self_string.partial_cmp(other_string),
                    (serde_json::Value::Array(self_array), serde_json::Value::Array(other_array)) => convert_vec_to_context_element(self_array).partial_cmp(&convert_vec_to_context_element(other_array)),
                    _ => None,
                };
            }
        }
        // Handle string literals
        match other.to_any().downcast_ref::<String>() {
            None => (),
            Some(other_string) => {
                return self
                    .as_str()
                    .map_or(None, |s| s.partial_cmp(other_string.as_str()))
            }
        }
        // Handle numeric literals
        match other.to_any().downcast_ref::<u64>() {
            None => (),
            Some(other_num) => return self.as_u64().map_or(None, |n| n.partial_cmp(other_num)),
        }
        None
    }
}

/// Create a new vec by of references to the serde_json::Values as
/// ContextElement trait objects so we can use its implementation of
/// PartialOrd.
///
/// You cannot implement a trait you do not define for a type you do
/// not define, so I cannot implement PartialOrd for
/// serde_json::value. Instead, I just re-use the PartialOrd
/// implementation for ContextElement which unfortunately has extra
/// overhead of downcasting. This would be a good spot for
/// optimization.
fn convert_vec_to_context_element(array: &Vec<serde_json::Value>) -> Vec<&dyn ContextElement> {
    array.iter().map(|v| v as _).collect()
}