use std::ffi::OsStr;
use std::path::PathBuf;

use include_dir::include_dir;
use include_dir::Dir;

use crate::blog_post::convert_blog_post_to_render_context;
use crate::blog_post::BlogPost;
use crate::error::CustomError;
use crate::render::DusterRenderer;
use crate::render::RendererIntegration;

static MAIN_TEMPLATES: Dir = include_dir!("$CARGO_MANIFEST_DIR/default_environment/templates/html");

pub(crate) struct SiteRenderer {
    output_directory: PathBuf,
    blog_posts: Vec<BlogPost>,
}

impl SiteRenderer {
    pub(crate) fn new<P: Into<PathBuf>>(
        output_directory: P,
        blog_posts: Vec<BlogPost>,
    ) -> SiteRenderer {
        SiteRenderer {
            output_directory: output_directory.into(),
            blog_posts,
        }
    }
    pub(crate) async fn render_blog_posts(&self) -> Result<(), CustomError> {
        let mut renderer_integration = DusterRenderer::new();

        let sources: Vec<_> = MAIN_TEMPLATES
            .files()
            .filter(|f| f.path().extension() == Some(OsStr::new("dust")))
            .collect();
        if sources
            .iter()
            .filter(|f| f.path().file_stem() == Some(OsStr::new("main")))
            .count()
            != 1
        {
            return Err("Expect exactly 1 main.dust template file.".into());
        }

        let decoded_templates = {
            let mut decoded_templates = Vec::with_capacity(sources.len());
            for entry in sources {
                decoded_templates.push(build_name_contents_pairs(entry)?);
            }
            decoded_templates
        };

        for (name, contents) in decoded_templates {
            renderer_integration.load_template(name, contents)?;
        }

        for blog_post in &self.blog_posts {
            let render_context = convert_blog_post_to_render_context(blog_post);
            let rendered_output = renderer_integration.render(render_context)?;
            println!("Rendered: {}", rendered_output);
        }

        Ok(())
    }
}

fn build_name_contents_pairs<'a>(
    entry: &'a include_dir::File<'_>,
) -> Result<(&'a str, &'a str), CustomError> {
    let path = entry.path();
    let name = path
        .file_stem()
        .ok_or("All templates should have a stem.")?
        .to_str()
        .ok_or("All template filenames should be valid utf-8.")?;
    let contents = std::str::from_utf8(entry.contents())?;
    Ok((name, contents))
}