use deno_core::OpState;
use deno_core::ToV8;
use deno_core::op2;
use nix_compat::nixhash::HashAlgo;
use nix_compat::nixhash::NixHash;
use tracing::{debug, info, warn};

use crate::store::Store as _;

mod archive;
pub(crate) mod cache;
mod download;
mod git;
mod metadata_cache;

pub use cache::FetcherCache;
pub use download::Downloader;
pub use metadata_cache::MetadataCache;

use crate::nar;

#[derive(ToV8)]
pub struct FetchUrlResult {
    pub store_path: String,
    pub hash: String,
}

#[derive(ToV8)]
pub struct FetchTarballResult {
    pub store_path: String,
    pub nar_hash: String,
}

#[derive(ToV8)]
pub struct FetchGitResult {
    pub out_path: String,
    pub rev: String,
    pub short_rev: String,
    pub rev_count: u64,
    pub last_modified: u64,
    pub last_modified_date: String,
    pub submodules: bool,
    pub nar_hash: Option<String>,
}

#[op2]
pub fn op_fetch_url<Ctx: RuntimeContext>(
    state: &mut OpState,
    #[string] url: String,
    #[string] expected_hash: Option<String>,
    #[string] name: Option<String>,
    executable: bool,
) -> Result<FetchUrlResult, NixRuntimeError> {
    let _span = tracing::info_span!("op_fetch_url", url = %url).entered();
    info!("fetchurl started");

    let file_name =
        name.unwrap_or_else(|| url.rsplit('/').next().unwrap_or("download").to_string());

    let metadata_cache =
        MetadataCache::new(3600).map_err(|e| NixRuntimeError::from(e.to_string()))?;

    let input = serde_json::json!({
        "type": "file",
        "url": url,
        "name": file_name,
        "executable": executable,
    });

    if let Some(cached_entry) = metadata_cache
        .lookup(&input)
        .map_err(|e| NixRuntimeError::from(e.to_string()))?
    {
        let cached_hash = cached_entry
            .info
            .get("hash")
            .and_then(|v| v.as_str())
            .unwrap_or("");

        if let Some(ref expected) = expected_hash {
            let normalized_expected = normalize_hash(expected);
            if cached_hash != normalized_expected {
                warn!("Cached hash mismatch, re-fetching");
            } else {
                info!("Cache hit");
                return Ok(FetchUrlResult {
                    store_path: cached_entry.store_path.clone(),
                    hash: cached_hash.to_string(),
                });
            }
        } else {
            info!("Cache hit (no hash check)");
            return Ok(FetchUrlResult {
                store_path: cached_entry.store_path.clone(),
                hash: cached_hash.to_string(),
            });
        }
    }

    info!("Cache miss, downloading");
    let downloader = Downloader::new();
    let data = downloader
        .download(&url)
        .map_err(|e| NixRuntimeError::from(e.to_string()))?;

    info!(bytes = data.len(), "Download complete");

    let hash = crate::nix_utils::sha256_hex(&data);

    if let Some(ref expected) = expected_hash {
        let normalized_expected = normalize_hash(expected);
        if hash != normalized_expected {
            return Err(NixRuntimeError::from(format!(
                "hash mismatch for '{}': expected {}, got {}",
                url, normalized_expected, hash
            )));
        }
    }

    let ctx: &Ctx = state.get_ctx();
    let store = ctx.get_store();
    let store_path = store
        .add_to_store(&file_name, &data, false, vec![])
        .map_err(|e| NixRuntimeError::from(e.to_string()))?;

    info!(store_path = %store_path, "Added to store");

    #[cfg(unix)]
    if executable {
        use std::os::unix::fs::PermissionsExt;
        if let Ok(metadata) = std::fs::metadata(&store_path) {
            let mut perms = metadata.permissions();
            perms.set_mode(0o755);
            let _ = std::fs::set_permissions(&store_path, perms);
        }
    }

    let info = serde_json::json!({
        "hash": hash,
        "url": url,
    });

    metadata_cache
        .add(&input, &info, &store_path, true)
        .map_err(|e| NixRuntimeError::from(e.to_string()))?;

    Ok(FetchUrlResult { store_path, hash })
}

#[op2]
pub fn op_fetch_tarball<Ctx: RuntimeContext>(
    state: &mut OpState,
    #[string] url: String,
    #[string] name: Option<String>,
    #[string] sha256: Option<String>,
) -> Result<FetchTarballResult, NixRuntimeError> {
    let _span = tracing::info_span!("op_fetch_tarball", url = %url).entered();
    info!("fetchTarball started");

    let dir_name = name.unwrap_or_else(|| "source".to_string());
    let metadata_cache =
        MetadataCache::new(3600).map_err(|e| NixRuntimeError::from(e.to_string()))?;

    let input = serde_json::json!({
        "type": "tarball",
        "url": url,
        "name": dir_name,
    });

    let expected_sha256 = sha256
        .map(
            |ref sha256| match NixHash::from_str(sha256, Some(HashAlgo::Sha256)) {
                Ok(NixHash::Sha256(digest)) => Ok(digest),
                _ => Err(format!("fetchTarball: invalid sha256 '{sha256}'")),
            },
        )
        .transpose()?;
    let expected_hex = expected_sha256.map(hex::encode);

    if let Some(cached_entry) = metadata_cache
        .lookup(&input)
        .map_err(|e| NixRuntimeError::from(e.to_string()))?
    {
        let cached_nar_hash = cached_entry
            .info
            .get("nar_hash")
            .and_then(|v| v.as_str())
            .unwrap_or("");

        if let Some(ref hex) = expected_hex {
            if cached_nar_hash == hex {
                info!("Cache hit");
                return Ok(FetchTarballResult {
                    store_path: cached_entry.store_path.clone(),
                    nar_hash: cached_nar_hash.to_string(),
                });
            }
        } else if !cached_entry.is_expired(3600) {
            info!("Cache hit (no hash check)");
            return Ok(FetchTarballResult {
                store_path: cached_entry.store_path.clone(),
                nar_hash: cached_nar_hash.to_string(),
            });
        }
    }

    info!("Cache miss, downloading tarball");
    let downloader = Downloader::new();
    let data = downloader
        .download(&url)
        .map_err(|e| NixRuntimeError::from(e.to_string()))?;

    info!(bytes = data.len(), "Download complete");

    info!("Extracting tarball");
    let (extracted_path, _temp_dir) = archive::extract_tarball_to_temp(&data)
        .map_err(|e| NixRuntimeError::from(e.to_string()))?;

    info!("Computing NAR hash");
    let nar_hash =
        nar::compute_nar_hash(&extracted_path).map_err(|e| NixRuntimeError::from(e.to_string()))?;
    let nar_hash_hex = hex::encode(nar_hash);

    debug!(
        nar_hash = %nar_hash_hex,
        "Hash computation complete"
    );

    if let Some(ref expected) = expected_hex
        && nar_hash_hex != *expected
    {
        return Err(NixRuntimeError::from(format!(
            "Tarball hash mismatch for '{}': expected {}, got {}",
            url, expected, nar_hash_hex
        )));
    }

    info!("Adding to store");
    let ctx: &Ctx = state.get_ctx();
    let store = ctx.get_store();
    let store_path = store
        .add_to_store_from_path(&dir_name, &extracted_path, vec![])
        .map_err(|e| NixRuntimeError::from(e.to_string()))?;

    info!(store_path = %store_path, "Added to store");

    let info = serde_json::json!({
        "nar_hash": nar_hash_hex,
        "url": url,
    });

    let immutable = expected_sha256.is_some();
    metadata_cache
        .add(&input, &info, &store_path, immutable)
        .map_err(|e| NixRuntimeError::from(e.to_string()))?;

    Ok(FetchTarballResult {
        store_path,
        nar_hash: nar_hash_hex,
    })
}

#[op2]
pub fn op_fetch_git<Ctx: RuntimeContext>(
    state: &mut OpState,
    #[string] url: String,
    #[string] git_ref: Option<String>,
    #[string] rev: Option<String>,
    shallow: bool,
    submodules: bool,
    all_refs: bool,
    #[string] name: Option<String>,
) -> Result<FetchGitResult, NixRuntimeError> {
    let _span = tracing::info_span!("op_fetch_git", url = %url).entered();
    info!("fetchGit started");
    let cache = FetcherCache::new().map_err(|e| NixRuntimeError::from(e.to_string()))?;
    let dir_name = name.unwrap_or_else(|| "source".to_string());

    let ctx: &Ctx = state.get_ctx();
    let store = ctx.get_store();

    git::fetch_git(
        &cache,
        store,
        &url,
        git_ref.as_deref(),
        rev.as_deref(),
        shallow,
        submodules,
        all_refs,
        &dir_name,
    )
    .map_err(|e| NixRuntimeError::from(e.to_string()))
}

fn normalize_hash(hash: &str) -> String {
    use base64::prelude::*;
    if hash.starts_with("sha256-")
        && let Some(b64) = hash.strip_prefix("sha256-")
        && let Ok(bytes) = BASE64_STANDARD.decode(b64)
    {
        return hex::encode(bytes);
    }
    hash.to_string()
}