use std::fs;
use std::path::{Component, Path, PathBuf};

use anyhow::Result;
use axum::body::Body;
use axum::extract::{OriginalUri, Path as AxumPath, State};
use axum::http::{StatusCode, header};
use axum::response::{IntoResponse, Redirect, Response};
use include_dir::{Dir, include_dir};

use crate::generate::{MANIFEST_FILE, STATE_FILE, STYLESHEET};
use crate::render::encode_path;

use super::{AppState, WebResult, internal, x_accel};

/// Bundle first: `cd web && deno task build`.
static WEB_DIST: Dir<'_> = include_dir!("$CARGO_MANIFEST_DIR/web/dist");
static FONTS: Dir<'_> = include_dir!("$CARGO_MANIFEST_DIR/assets/fonts");

pub(super) fn stage_assets(cache: &Path) -> Result<()> {
    // Embedded assets are served via X-Accel like everything else, so nginx
    // provides ETag/Last-Modified/304s. Write only on change to keep the
    // mtime-derived ETags stable across restarts.
    write_asset(&cache.join("css/style.css"), STYLESHEET.as_bytes())?;
    write_embedded_dir(&WEB_DIST, &cache.join("js"))?;
    write_embedded_dir(&FONTS, &cache.join("fonts"))
}

fn write_embedded_dir(dir: &Dir<'_>, out: &Path) -> Result<()> {
    for file in dir.files() {
        write_asset(&out.join(file.path()), file.contents())?;
    }
    for child in dir.dirs() {
        write_embedded_dir(child, out)?;
    }
    Ok(())
}

fn write_asset(path: &Path, content: &[u8]) -> Result<()> {
    if fs::read(path).ok().as_deref() != Some(content) {
        fs::create_dir_all(path.parent().expect("asset path has a parent"))?;
        fs::write(path, content)?;
    }
    Ok(())
}

pub(super) async fn index(State(state): State<AppState>) -> Response {
    let html = state.snapshot.load().catalog_html.clone();
    (
        [(header::CONTENT_TYPE, "text/html; charset=utf-8")],
        Body::from(html),
    )
        .into_response()
}

pub(super) async fn stylesheet(State(state): State<AppState>) -> WebResult<Response> {
    serve_cache_path(&state, "css/style.css")
}

pub(super) async fn js_asset(
    State(state): State<AppState>,
    AxumPath(path): AxumPath<String>,
) -> WebResult<Response> {
    embedded_asset(&state, &WEB_DIST, "js", &path)
}

pub(super) async fn font_asset(
    State(state): State<AppState>,
    AxumPath(path): AxumPath<String>,
) -> WebResult<Response> {
    embedded_asset(&state, &FONTS, "fonts", &path)
}

fn embedded_asset(
    state: &AppState,
    dir: &Dir<'_>,
    prefix: &str,
    path: &str,
) -> WebResult<Response> {
    if dir.get_file(path).is_none() {
        return Err((StatusCode::NOT_FOUND, "not found".into()));
    }
    serve_cache_path(state, &format!("{prefix}/{}", encode_path(path)))
}

pub(super) async fn add_trailing_slash(OriginalUri(uri): OriginalUri) -> Redirect {
    Redirect::permanent(&format!("{}/", uri.path()))
}

pub(super) async fn repo_root(
    State(state): State<AppState>,
    OriginalUri(uri): OriginalUri,
    AxumPath((user, repo)): AxumPath<(String, String)>,
) -> WebResult<Response> {
    serve_repo(state, user, repo, String::new(), uri.path().to_owned()).await
}

pub(super) async fn repo_path(
    State(state): State<AppState>,
    OriginalUri(uri): OriginalUri,
    AxumPath((user, repo, path)): AxumPath<(String, String, String)>,
) -> WebResult<Response> {
    serve_repo(state, user, repo, path, uri.path().to_owned()).await
}

async fn serve_repo(
    state: AppState,
    user: String,
    name: String,
    path: String,
    request_path: String,
) -> WebResult<Response> {
    let entry = state.resolve(&user, &name)?;
    let relative = requested_file(&path)?;
    let output = state.config.repo_cache(&entry.repository);
    if !output.join(STATE_FILE).is_file() {
        state.build(&entry).await.map_err(internal)?;
    }

    let target = output.join(&relative);
    if target.is_dir() {
        return Ok(Redirect::permanent(&format!("{request_path}/")).into_response());
    }
    if !target.is_file() {
        return Err((StatusCode::NOT_FOUND, "page not found".into()));
    }

    serve_cache_path(
        &state,
        &format!(
            "{}/{}/{}",
            encode_path(&entry.repository.user),
            encode_path(&entry.repository.name),
            encode_path(&relative.to_string_lossy()),
        ),
    )
}

fn serve_cache_path(state: &AppState, encoded_path: &str) -> WebResult<Response> {
    x_accel(&state.config.internal_prefix, encoded_path)
}

fn requested_file(path: &str) -> WebResult<PathBuf> {
    if path.is_empty() {
        return Ok(PathBuf::from("index.html"));
    }
    if path == STATE_FILE || path == MANIFEST_FILE {
        return Err((StatusCode::NOT_FOUND, "page not found".into()));
    }
    let directory = path.ends_with('/');
    let path = Path::new(path);
    if path
        .components()
        .any(|component| !matches!(component, Component::Normal(_)))
    {
        return Err((StatusCode::BAD_REQUEST, "invalid path".into()));
    }
    Ok(if directory {
        path.join("index.html")
    } else {
        path.to_owned()
    })
}

#[cfg(test)]
mod tests {
    use crate::generate::{MANIFEST_FILE, STATE_FILE};

    use super::requested_file;

    #[test]
    fn generator_metadata_is_private() {
        assert!(requested_file(STATE_FILE).is_err());
        assert!(requested_file(MANIFEST_FILE).is_err());
    }
}