use crate::ExtensionManifest;
use crate::{extension_manifest::ExtensionLibraryKind, GrammarManifestEntry};
use anyhow::{anyhow, bail, Context as _, Result};
use async_compression::futures::bufread::GzipDecoder;
use async_tar::Archive;
use futures::io::BufReader;
use futures::AsyncReadExt;
use serde::Deserialize;
use std::mem;
use std::{
    env, fs,
    path::{Path, PathBuf},
    process::{Command, Stdio},
    sync::Arc,
};
use util::http::{self, AsyncBody, HttpClient};
use wasm_encoder::{ComponentSectionId, Encode as _, RawSection, Section as _};
use wasmparser::Parser;
use wit_component::ComponentEncoder;

/// Currently, we compile with Rust's `wasm32-wasi` target, which works with WASI `preview1`.
/// But the WASM component model is based on WASI `preview2`. So we need an 'adapter' WASM
/// module, which implements the `preview1` interface in terms of `preview2`.
///
/// Once Rust 1.78 is released, there will be a `wasm32-wasip2` target available, so we will
/// not need the adapter anymore.
const RUST_TARGET: &str = "wasm32-wasi";
const WASI_ADAPTER_URL: &str =
    "https://github.com/bytecodealliance/wasmtime/releases/download/v18.0.2/wasi_snapshot_preview1.reactor.wasm";

/// Compiling Tree-sitter parsers from C to WASM requires Clang 17, and a WASM build of libc
/// and clang's runtime library. The `wasi-sdk` provides these binaries.
///
/// Once Clang 17 and its wasm target are available via system package managers, we won't need
/// to download this.
const WASI_SDK_URL: &str = "https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-21/";
const WASI_SDK_ASSET_NAME: Option<&str> = if cfg!(target_os = "macos") {
    Some("wasi-sdk-21.0-macos.tar.gz")
} else if cfg!(target_os = "linux") {
    Some("wasi-sdk-21.0-linux.tar.gz")
} else {
    None
};

pub struct ExtensionBuilder {
    cache_dir: PathBuf,
    pub http: Arc<dyn HttpClient>,
}

pub struct CompileExtensionOptions {
    pub release: bool,
}

#[derive(Deserialize)]
struct CargoToml {
    package: CargoTomlPackage,
}

#[derive(Deserialize)]
struct CargoTomlPackage {
    name: String,
}

impl ExtensionBuilder {
    pub fn new(cache_dir: PathBuf) -> Self {
        Self {
            cache_dir,
            http: http::client(),
        }
    }

    pub async fn compile_extension(
        &self,
        extension_dir: &Path,
        options: CompileExtensionOptions,
    ) -> Result<()> {
        fs::create_dir_all(&self.cache_dir)?;
        let extension_toml_path = extension_dir.join("extension.toml");
        let extension_toml_content = fs::read_to_string(&extension_toml_path)?;
        let extension_toml: ExtensionManifest = toml::from_str(&extension_toml_content)?;

        let cargo_toml_path = extension_dir.join("Cargo.toml");
        if extension_toml.lib.kind == Some(ExtensionLibraryKind::Rust)
            || fs::metadata(&cargo_toml_path)?.is_file()
        {
            self.compile_rust_extension(extension_dir, options).await?;
        }

        for (grammar_name, grammar_metadata) in extension_toml.grammars {
            self.compile_grammar(extension_dir, grammar_name, grammar_metadata)
                .await?;
        }

        log::info!("finished compiling extension {}", extension_dir.display());
        Ok(())
    }

    async fn compile_rust_extension(
        &self,
        extension_dir: &Path,
        options: CompileExtensionOptions,
    ) -> Result<(), anyhow::Error> {
        self.install_rust_wasm_target_if_needed()?;
        let adapter_bytes = self.install_wasi_preview1_adapter_if_needed().await?;

        let cargo_toml_content = fs::read_to_string(&extension_dir.join("Cargo.toml"))?;
        let cargo_toml: CargoToml = toml::from_str(&cargo_toml_content)?;

        log::info!("compiling rust extension {}", extension_dir.display());
        let output = Command::new("cargo")
            .args(["build", "--target", RUST_TARGET])
            .args(options.release.then_some("--release"))
            .arg("--target-dir")
            .arg(extension_dir.join("target"))
            .current_dir(&extension_dir)
            .output()
            .context("failed to run `cargo`")?;
        if !output.status.success() {
            bail!(
                "failed to build extension {}",
                String::from_utf8_lossy(&output.stderr)
            );
        }

        let mut wasm_path = PathBuf::from(extension_dir);
        wasm_path.extend([
            "target",
            RUST_TARGET,
            if options.release { "release" } else { "debug" },
            cargo_toml.package.name.as_str(),
        ]);
        wasm_path.set_extension("wasm");

        let wasm_bytes = fs::read(&wasm_path)
            .with_context(|| format!("failed to read output module `{}`", wasm_path.display()))?;

        let encoder = ComponentEncoder::default()
            .module(&wasm_bytes)?
            .adapter("wasi_snapshot_preview1", &adapter_bytes)
            .context("failed to load adapter module")?
            .validate(true);

        let component_bytes = encoder
            .encode()
            .context("failed to encode wasm component")?;

        let component_bytes = self
            .strip_custom_sections(&component_bytes)
            .context("failed to strip debug sections from wasm component")?;

        fs::write(extension_dir.join("extension.wasm"), &component_bytes)
            .context("failed to write extension.wasm")?;

        Ok(())
    }

    async fn compile_grammar(
        &self,
        extension_dir: &Path,
        grammar_name: Arc<str>,
        grammar_metadata: GrammarManifestEntry,
    ) -> Result<()> {
        let clang_path = self.install_wasi_sdk_if_needed().await?;

        let mut grammar_repo_dir = extension_dir.to_path_buf();
        grammar_repo_dir.extend(["grammars", grammar_name.as_ref()]);

        let mut grammar_wasm_path = grammar_repo_dir.clone();
        grammar_wasm_path.set_extension("wasm");

        log::info!("checking out {grammar_name} parser");
        self.checkout_repo(
            &grammar_repo_dir,
            &grammar_metadata.repository,
            &grammar_metadata.rev,
        )?;

        let src_path = grammar_repo_dir.join("src");
        let parser_path = src_path.join("parser.c");
        let scanner_path = src_path.join("scanner.c");

        log::info!("compiling {grammar_name} parser");
        let clang_output = Command::new(&clang_path)
            .args(["-fPIC", "-shared", "-Os"])
            .arg(format!("-Wl,--export=tree_sitter_{grammar_name}"))
            .arg("-o")
            .arg(&grammar_wasm_path)
            .arg("-I")
            .arg(&src_path)
            .arg(&parser_path)
            .args(scanner_path.exists().then_some(scanner_path))
            .output()
            .context("failed to run clang")?;
        if !clang_output.status.success() {
            bail!(
                "failed to compile {} parser with clang: {}",
                grammar_name,
                String::from_utf8_lossy(&clang_output.stderr),
            );
        }

        Ok(())
    }

    fn checkout_repo(&self, directory: &Path, url: &str, rev: &str) -> Result<()> {
        let git_dir = directory.join(".git");

        if directory.exists() {
            let remotes_output = Command::new("git")
                .arg("--git-dir")
                .arg(&git_dir)
                .args(["remote", "-v"])
                .output()?;
            let has_remote = remotes_output.status.success()
                && String::from_utf8_lossy(&remotes_output.stdout)
                    .lines()
                    .any(|line| {
                        let mut parts = line.split(|c: char| c.is_whitespace());
                        parts.next() == Some("origin") && parts.any(|part| part == url)
                    });
            if !has_remote {
                bail!(
                    "grammar directory '{}' already exists, but is not a git clone of '{}'",
                    directory.display(),
                    url
                );
            }
        } else {
            fs::create_dir_all(&directory).with_context(|| {
                format!("failed to create grammar directory {}", directory.display(),)
            })?;
            let init_output = Command::new("git")
                .arg("init")
                .current_dir(&directory)
                .output()?;
            if !init_output.status.success() {
                bail!(
                    "failed to run `git init` in directory '{}'",
                    directory.display()
                );
            }

            let remote_add_output = Command::new("git")
                .arg("--git-dir")
                .arg(&git_dir)
                .args(["remote", "add", "origin", url])
                .output()
                .context("failed to execute `git remote add`")?;
            if !remote_add_output.status.success() {
                bail!(
                    "failed to add remote {url} for git repository {}",
                    git_dir.display()
                );
            }
        }

        let fetch_output = Command::new("git")
            .arg("--git-dir")
            .arg(&git_dir)
            .args(["fetch", "--depth", "1", "origin", &rev])
            .output()
            .context("failed to execute `git fetch`")?;

        let checkout_output = Command::new("git")
            .arg("--git-dir")
            .arg(&git_dir)
            .args(["checkout", &rev])
            .current_dir(&directory)
            .output()
            .context("failed to execute `git checkout`")?;
        if !checkout_output.status.success() {
            if !fetch_output.status.success() {
                bail!(
                    "failed to fetch revision {} in directory '{}'",
                    rev,
                    directory.display()
                );
            }
            bail!(
                "failed to checkout revision {} in directory '{}'",
                rev,
                directory.display()
            );
        }

        Ok(())
    }

    fn install_rust_wasm_target_if_needed(&self) -> Result<()> {
        let rustc_output = Command::new("rustc")
            .arg("--print")
            .arg("sysroot")
            .output()
            .context("failed to run rustc")?;
        if !rustc_output.status.success() {
            bail!(
                "failed to retrieve rust sysroot: {}",
                String::from_utf8_lossy(&rustc_output.stderr)
            );
        }

        let sysroot = PathBuf::from(String::from_utf8(rustc_output.stdout)?.trim());
        if sysroot.join("lib/rustlib").join(RUST_TARGET).exists() {
            return Ok(());
        }

        let output = Command::new("rustup")
            .args(["target", "add", RUST_TARGET])
            .stderr(Stdio::inherit())
            .stdout(Stdio::inherit())
            .output()
            .context("failed to run `rustup target add`")?;
        if !output.status.success() {
            bail!("failed to install the `{RUST_TARGET}` target");
        }

        Ok(())
    }

    async fn install_wasi_preview1_adapter_if_needed(&self) -> Result<Vec<u8>> {
        let cache_path = self.cache_dir.join("wasi_snapshot_preview1.reactor.wasm");
        if let Ok(content) = fs::read(&cache_path) {
            if Parser::is_core_wasm(&content) {
                return Ok(content);
            }
        }

        fs::remove_file(&cache_path).ok();

        log::info!(
            "downloading wasi adapter module to {}",
            cache_path.display()
        );
        let mut response = self
            .http
            .get(WASI_ADAPTER_URL, AsyncBody::default(), true)
            .await?;

        let mut content = Vec::new();
        let mut body = BufReader::new(response.body_mut());
        body.read_to_end(&mut content).await?;

        fs::write(&cache_path, &content)
            .with_context(|| format!("failed to save file {}", cache_path.display()))?;

        if !Parser::is_core_wasm(&content) {
            bail!("downloaded wasi adapter is invalid");
        }
        Ok(content)
    }

    async fn install_wasi_sdk_if_needed(&self) -> Result<PathBuf> {
        let url = if let Some(asset_name) = WASI_SDK_ASSET_NAME {
            format!("{WASI_SDK_URL}/{asset_name}")
        } else {
            bail!("wasi-sdk is not available for platform {}", env::consts::OS);
        };

        let wasi_sdk_dir = self.cache_dir.join("wasi-sdk");
        let mut clang_path = wasi_sdk_dir.clone();
        clang_path.extend(["bin", "clang-17"]);

        if fs::metadata(&clang_path).map_or(false, |metadata| metadata.is_file()) {
            return Ok(clang_path);
        }

        let mut tar_out_dir = wasi_sdk_dir.clone();
        tar_out_dir.set_extension("archive");

        fs::remove_dir_all(&wasi_sdk_dir).ok();
        fs::remove_dir_all(&tar_out_dir).ok();

        log::info!("downloading wasi-sdk to {}", wasi_sdk_dir.display());
        let mut response = self.http.get(&url, AsyncBody::default(), true).await?;
        let body = BufReader::new(response.body_mut());
        let body = GzipDecoder::new(body);
        let tar = Archive::new(body);
        tar.unpack(&tar_out_dir)
            .await
            .context("failed to unpack wasi-sdk archive")?;

        let inner_dir = fs::read_dir(&tar_out_dir)?
            .next()
            .ok_or_else(|| anyhow!("no content"))?
            .context("failed to read contents of extracted wasi archive directory")?
            .path();
        fs::rename(&inner_dir, &wasi_sdk_dir).context("failed to move extracted wasi dir")?;
        fs::remove_dir_all(&tar_out_dir).ok();

        Ok(clang_path)
    }

    // This was adapted from:
    // https://github.com/bytecodealliance/wasm-tools/1791a8f139722e9f8679a2bd3d8e423e55132b22/src/bin/wasm-tools/strip.rs
    fn strip_custom_sections(&self, input: &Vec<u8>) -> Result<Vec<u8>> {
        use wasmparser::Payload::*;

        let strip_custom_section = |name: &str| name.starts_with(".debug");

        let mut output = Vec::new();
        let mut stack = Vec::new();

        for payload in Parser::new(0).parse_all(input) {
            let payload = payload?;

            // Track nesting depth, so that we don't mess with inner producer sections:
            match payload {
                Version { encoding, .. } => {
                    output.extend_from_slice(match encoding {
                        wasmparser::Encoding::Component => &wasm_encoder::Component::HEADER,
                        wasmparser::Encoding::Module => &wasm_encoder::Module::HEADER,
                    });
                }
                ModuleSection { .. } | ComponentSection { .. } => {
                    stack.push(mem::take(&mut output));
                    continue;
                }
                End { .. } => {
                    let mut parent = match stack.pop() {
                        Some(c) => c,
                        None => break,
                    };
                    if output.starts_with(&wasm_encoder::Component::HEADER) {
                        parent.push(ComponentSectionId::Component as u8);
                        output.encode(&mut parent);
                    } else {
                        parent.push(ComponentSectionId::CoreModule as u8);
                        output.encode(&mut parent);
                    }
                    output = parent;
                }
                _ => {}
            }

            match &payload {
                CustomSection(c) => {
                    if strip_custom_section(c.name()) {
                        continue;
                    }
                }

                _ => {}
            }

            if let Some((id, range)) = payload.as_section() {
                RawSection {
                    id,
                    data: &input[range],
                }
                .append_to(&mut output);
            }
        }

        Ok(output)
    }
}