use std::path::Component;
use std::path::Path;
use std::path::PathBuf;

use crate::config::Config;
use crate::error::CustomError;
use crate::types::GlobalSettings;
use crate::types::RenderBlogPostPage;

use super::BlogPost;
use super::BlogPostPage;

pub(crate) fn convert_blog_post_page_to_render_context<D: AsRef<Path>, F: AsRef<Path>>(
    config: &Config,
    output_directory: D,
    output_file: F,
    _post: &BlogPost,
    page: &BlogPostPage,
) -> Result<RenderBlogPostPage, CustomError> {
    let output_directory = output_directory.as_ref();
    let output_file = output_file.as_ref();
    let css_files = vec![get_web_path(
        config,
        output_directory,
        output_file,
        "main.css",
    )?];
    let js_files = vec![get_web_path(
        config,
        output_directory,
        output_file,
        "blog_post.js",
    )?];
    let global_settings = GlobalSettings::new(page.title.clone(), css_files, js_files);
    let link_to_blog_post = get_web_path(
        config,
        output_directory,
        output_file,
        output_file.strip_prefix(output_directory)?,
    )?;

    let ret = RenderBlogPostPage::new(global_settings, page.title.clone(), Some(link_to_blog_post));
    Ok(ret)
}

fn get_web_path<D: AsRef<Path>, F: AsRef<Path>, P: AsRef<Path>>(
    config: &Config,
    output_directory: D,
    containing_file: F,
    path_from_web_root: P,
) -> Result<String, CustomError> {
    let path_from_web_root = path_from_web_root.as_ref();
    if config.use_relative_paths() {
        let output_directory = output_directory.as_ref();
        let containing_file = containing_file.as_ref();
        let containing_file_relative_to_output_directory =
            containing_file.strip_prefix(output_directory)?;
        let shared_stem = get_shared_steps(
            containing_file_relative_to_output_directory
                .parent()
                .ok_or("File should exist in a folder.")?,
            path_from_web_root
                .parent()
                .ok_or("File should exist in a folder.")?,
        )
        .collect::<PathBuf>();
        // Subtracting 1 from the depth to "remove" the file name.
        let depth_from_shared_stem = containing_file_relative_to_output_directory
            .strip_prefix(&shared_stem)?
            .components()
            .count()
            - 1;
        let final_path = PathBuf::from("../".repeat(depth_from_shared_stem))
            .join(path_from_web_root.strip_prefix(shared_stem)?);
        let final_string = final_path
            .as_path()
            .to_str()
            .map(str::to_string)
            .ok_or("Path should be valid utf-8.")?;
        Ok(final_string)
    } else {
        let web_root = config
            .get_web_root()
            .ok_or("Must either use_relative_paths or set the web_root in the config.")?;
        let final_path = PathBuf::from(web_root).join(path_from_web_root);
        let final_string = final_path
            .as_path()
            .to_str()
            .map(str::to_string)
            .ok_or("Path should be valid utf-8.")?;
        Ok(final_string)
    }
}

fn get_shared_steps<'a>(left: &'a Path, right: &'a Path) -> impl Iterator<Item = Component<'a>> {
    let shared_stem = left
        .components()
        .zip(right.components())
        .take_while(|(l, r)| l == r)
        .map(|(l, _r)| l);
    shared_stem
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_get_shared_steps() {
        assert_eq!(
            get_shared_steps(Path::new(""), Path::new("")).collect::<PathBuf>(),
            PathBuf::from("")
        );
        assert_eq!(
            get_shared_steps(Path::new("foo.txt"), Path::new("foo.txt")).collect::<PathBuf>(),
            PathBuf::from("foo.txt")
        );
        assert_eq!(
            get_shared_steps(Path::new("cat/foo.txt"), Path::new("dog/foo.txt"))
                .collect::<PathBuf>(),
            PathBuf::from("")
        );
        assert_eq!(
            get_shared_steps(
                Path::new("foo/bar/baz/lorem.txt"),
                Path::new("foo/bar/ipsum/dolar.txt")
            )
            .collect::<PathBuf>(),
            PathBuf::from("foo/bar")
        );
    }
}