use std::path::PathBuf;

use time::{OffsetDateTime, PrimitiveDateTime, UtcDateTime, UtcOffset};
use tracing::info;
use typst::{
    Library, LibraryExt, World,
    diag::{FileError, FileResult, PackageError, PackageResult, SourceDiagnostic},
    foundations::{Bytes, Datetime, Dict, Duration, Value},
    syntax::{FileId, RootedPath, Source, VirtualPath, VirtualRoot, package::PackageSpec},
    text::{Font, FontBook},
    utils::LazyHash,
};
use typst_html::HtmlOptions;
use typst_kit::fonts::FontStore;

use crate::AppConfig;

pub struct TypstContext {
    config: AppConfig,
    library: LazyHash<Library>,
    fonts: FontStore,
}

impl TypstContext {
    pub fn new(config: AppConfig) -> Self {
        let mut inputs = Dict::new();
        if config.syntax_root.is_some() {
            inputs.insert(
                "highlight".into(),
                Value::Func(crate::syntax::highlight_func()),
            );
        }
        let library = Library::builder()
            .with_inputs(inputs)
            .with_features([typst::Feature::Html].into_iter().collect())
            .build();
        let library = LazyHash::new(library);
        let fonts = FontStore::new();

        Self {
            config,
            library,
            fonts,
        }
    }

    // TODO: Better return error
    pub fn compile_document(&self, path: VirtualPath) -> Result<String, Vec<SourceDiagnostic>> {
        info!("Compiling {:?}", &path);
        let world = DocumentWorld::new(path, self);
        let compiled = typst::compile(&world);

        let html_options = HtmlOptions::default();

        // TODO: Log warnings

        // TODO: Log errors
        compiled
            .output
            .and_then(|doc| typst_html::html(&doc, &html_options))
            .map_err(|err| err.into_iter().collect())
    }
}

struct DocumentWorld<'a> {
    main: FileId,
    now: UtcDateTime,
    context: &'a TypstContext,
}

impl<'a> World for DocumentWorld<'a> {
    fn library(&self) -> &LazyHash<Library> {
        &self.context.library
    }

    fn book(&self) -> &LazyHash<FontBook> {
        self.context.fonts.book()
    }

    fn main(&self) -> FileId {
        self.main
    }

    fn source(&self, id: FileId) -> FileResult<Source> {
        self.resolve_file(id).and_then(|path| {
            let text = std::fs::read_to_string(&path).map_err(|e| FileError::from_io(e, &path))?;
            Ok(Source::new(id, text))
        })
    }

    fn file(&self, id: FileId) -> FileResult<Bytes> {
        self.resolve_file(id).and_then(|path| {
            let bytes = std::fs::read(&path).map_err(|e| FileError::from_io(e, &path))?;
            Ok(Bytes::new(bytes))
        })
    }

    fn font(&self, index: usize) -> Option<Font> {
        self.context.fonts.font(index)
    }

    fn today(&self, offset: Option<Duration>) -> Option<Datetime> {
        let offset = offset
            .map(|v| v.seconds() as i32)
            .and_then(|v| UtcOffset::from_whole_seconds(v).ok())
            .unwrap_or(UtcOffset::UTC);
        let datetime = OffsetDateTime::from(self.now).replace_offset(offset);
        let datetime = PrimitiveDateTime::new(datetime.date(), datetime.time());
        Some(Datetime::Datetime(datetime))
    }
}

impl<'a> DocumentWorld<'a> {
    fn new(path: VirtualPath, context: &'a TypstContext) -> Self {
        let main = FileId::new(RootedPath::new(VirtualRoot::Project, path));
        let now = UtcDateTime::now();

        Self { main, now, context }
    }

    fn resolve_file(&self, id: FileId) -> FileResult<PathBuf> {
        let path = id.vpath();
        match id.root() {
            VirtualRoot::Project => self.resolve_project_file(path),
            VirtualRoot::Package(package_spec) => self.resolve_package_file(path, package_spec),
        }
    }

    fn resolve_project_file(&self, path: &VirtualPath) -> FileResult<PathBuf> {
        path.realize(&self.context.config.content_root)
            .map_err(FileError::Realize)
    }

    fn resolve_package_file(&self, path: &VirtualPath, spec: &PackageSpec) -> FileResult<PathBuf> {
        match spec.namespace.as_str() {
            "common" => self.resolve_common_file(path, spec),
            "preview" => self.resolve_preview_file(path, spec),
            _ => unimplemented!(),
        }
    }

    fn resolve_common_file(&self, path: &VirtualPath, spec: &PackageSpec) -> FileResult<PathBuf> {
        let path = get_package_path(path, spec);
        path.realize(&self.context.config.get_full_common_path())
            .map_err(FileError::Realize)
    }

    fn resolve_preview_file(&self, path: &VirtualPath, spec: &PackageSpec) -> FileResult<PathBuf> {
        let package_path = self.get_package(spec)?;
        path.realize(&package_path).map_err(FileError::Realize)
    }

    fn get_package(&self, spec: &PackageSpec) -> PackageResult<PathBuf> {
        let path = get_package_path(
            &VirtualPath::new("").expect("Failed to create empty virtual path"),
            spec,
        );
        let path = path
            .realize(&self.context.config.packages_root)
            .map_err(|_| PackageError::NotFound(spec.clone()))?;

        if path.exists() {
            return Ok(path);
        }

        let url = format!(
            "https://packages.typst.org/preview/{}-{}.tar.gz",
            spec.name, spec.version
        );

        info!("Downloading package from {}", url);

        let response = ureq::get(&url)
            .call()
            .map_err(|err| err.to_string())
            .and_then(|res| {
                if res.status().is_success() {
                    Ok(res)
                } else {
                    Err(format!("Received status code {}", res.status()))
                }
            })
            .map_err(|err| PackageError::NetworkFailed(Some(err.into())))?;

        let archive = response.into_body().into_reader();
        let archive = flate2::read::GzDecoder::new(archive);
        let mut archive = tar::Archive::new(archive);
        archive.unpack(&path).map_err(|err| {
            // let _ = std::fs::remove_dir_all(path.clone());
            PackageError::MalformedArchive(Some(err.to_string().into()))
        })?;

        Ok(path)
    }
}

fn get_package_path(file_path: &VirtualPath, spec: &PackageSpec) -> VirtualPath {
    let package_path = VirtualPath::new(format!("{}/{}", spec.name, spec.version))
        .expect("Failed to create virtual path representing package path.");
    package_path
        .join(file_path.get_without_slash())
        .expect("Failed to join file path into package path.")
}