use std::cell::RefCell;
use std::collections::HashSet;
use std::rc::Rc;
use std::sync::Arc;

use avril_runtime::caps::{Capabilities, Initial};
use avril_runtime::config_edit::{self, Addition, Change};
use avril_runtime::import_map::ImportMap;
use avril_runtime::package_config;
use avril_runtime::registry::{
    Options, PackageStore, ProgressEvent, ProgressSink, npm::resolution::NpmResolver,
    parse_jsr_request,
};
use futures::executor::block_on;

use crate::{cli, cli::ParseError};
use avril_runtime::modules::ModuleGraph;

pub struct Args {
    config: Option<String>,
    pre: bool,
    offline: bool,
    automatic_types: bool,
    jsr_registry: url::Url,
    npm_registry: url::Url,
    cache_dir: Option<String>,
    values: Vec<String>,
}

/// `avril add` argument parsing failed.
#[derive(Debug, thiserror::Error)]
pub enum AddParseError {
    #[error(transparent)]
    Generic(#[from] ParseError),
    #[error("Expected one config path")]
    DuplicateConfig,
    #[error("{0}")]
    Url(#[from] url::ParseError),
}

pub fn parse(args: &[String]) -> std::result::Result<Args, AddParseError> {
    let command = cli::command("add").ok_or_else(|| ParseError::Usage(cli::usage()))?;
    let mut parsed = Args {
        config: None,
        pre: false,
        offline: false,
        automatic_types: true,
        jsr_registry: url::Url::parse("https://jsr.io/").unwrap(),
        npm_registry: url::Url::parse("https://registry.npmjs.org/").unwrap(),
        cache_dir: None,
        values: Vec::new(),
    };
    for arg in args {
        if arg.starts_with('-') {
            command.check(arg).map_err(ParseError::Check)?;
        }
        match arg.as_str() {
            "--pre" => parsed.pre = true,
            "--offline" => parsed.offline = true,
            "--no-types-packages" => parsed.automatic_types = false,
            _ if arg.starts_with('-') => {
                let (flag, value) = match arg.split_once('=') {
                    Some((flag, value)) if !value.is_empty() => {
                        (flag.strip_prefix("--").unwrap_or(flag).to_owned(), value)
                    }
                    Some((flag, _)) => {
                        return Err(ParseError::MissingValue {
                            flag: flag.strip_prefix("--").unwrap_or(flag).to_owned(),
                            equals: "=",
                        }
                        .into());
                    }
                    None => {
                        return Err(ParseError::MissingValue {
                            flag: arg.strip_prefix("--").unwrap_or(arg).to_owned(),
                            equals: "",
                        }
                        .into());
                    }
                };
                match flag.as_str() {
                    "config" => {
                        if parsed.config.replace(value.to_owned()).is_some() {
                            return Err(AddParseError::DuplicateConfig);
                        }
                    }
                    "jsr-registry" => parsed.jsr_registry = url::Url::parse(value)?,
                    "npm-registry" => parsed.npm_registry = url::Url::parse(value)?,
                    "cache-dir" => parsed.cache_dir = Some(value.to_owned()),
                    _ => return Err(ParseError::UnexpectedValue { flag }.into()),
                }
            }
            _ => parsed.values.push(arg.clone()),
        }
    }
    Ok(parsed)
}

/// `avril add`: pins unversioned targets to the newest release, edits the config, then
/// caches what the new mapping can import, as `avril cache` would.
pub fn run(args: Args) -> Result<(), Box<dyn std::error::Error>> {
    let cwd = std::env::current_dir()?.canonicalize()?;
    let Args {
        config,
        pre,
        offline,
        automatic_types,
        jsr_registry,
        npm_registry,
        cache_dir,
        values,
    } = args;
    let cache = cache_dir
        .map(|dir| cwd.join(dir))
        .unwrap_or_else(|| cli::default_cache(&cwd));
    let config = config.map(|config| cwd.join(config));
    let command = cli::command("add").ok_or_else(cli::usage)?;
    let (alias, target) = match values.as_slice() {
        [target] => (None, target.as_str()),
        [alias, target] => (Some(alias.as_str()), target.as_str()),
        _ => return Err(command.usage().into()),
    };
    let caps = Capabilities::new(Initial::new(false), cwd.clone());
    let authority = avril_runtime::authority::SourceAuthority::execute(caps.clone());
    let config = match config {
        Some(config) => config,
        None => ModuleGraph::project_root_for_add(
            &authority,
            cwd.join("avril.conf")
                .to_str()
                .ok_or("Paths must be UTF-8")?,
        )?
        .join("avril.conf"),
    };
    let directory = config.parent().ok_or("Config needs a parent directory")?;
    let host = avril_host::Host::new()?;
    let store = Arc::new(
        PackageStore::new_with_authority(
            host.handle(),
            Options {
                jsr_registry,
                npm_registry,
                cache,
                lock: directory.join("avril.lock"),
                project_root: directory.to_owned(),
                offline,
                frozen: false,
                update: false,
                ephemeral_lock: false,
                vendor: None,
            },
            authority.clone(),
        )?
        .with_progress(progress_sink()),
    );
    let npm_target = target.starts_with("npm:");
    let target = match config_edit::unversioned(target)? {
        Some(name) => {
            if npm_target {
                if pre {
                    return Err(
                        "--pre does not apply to npm: targets; select a prerelease tag explicitly"
                            .into(),
                    );
                }
                phase(format!("Selecting version for {target:?}..."));
                let version = block_on(store.npm_select_version(target))?;
                config_edit::with_caret(target, &name, &version)
            } else {
                phase(format!("Selecting version for {target:?}..."));
                let version = block_on(store.latest(&name, pre))?.ok_or_else(|| {
                    if pre {
                        format!("{name} has no non-yanked versions")
                    } else {
                        format!(
                            "{name} has no non-yanked stable versions; --pre allows prereleases"
                        )
                    }
                })?;
                config_edit::with_caret(target, &name, &version)
            }
        }
        None if pre => {
            if npm_target {
                return Err(
                    "--pre does not apply to npm: targets; select a prerelease tag explicitly"
                        .into(),
                );
            }
            return Err("--pre only applies to targets without a version".into());
        }
        None => target.to_owned(),
    };
    let package = config_edit::whole_package(&target)?;
    // Packages belong in deps; only an alias for a subpath or prefix needs imports.
    let addition = match alias {
        Some(alias)
            if !config_edit::selects_whole_package(&target)?
                || !package_config::valid_name(alias) =>
        {
            Addition::Import { alias, target: &target }
        }
        name => Addition::Dependency { name, package: &package },
    };
    let binding = addition.binding()?;
    let change = config_edit::add_file(&config, &addition)?;
    report(&change, &binding, addition.target(), &config, &cwd);
    let prefix = match addition {
        Addition::Import { alias, target } if alias.ends_with('/') => {
            Some((alias.to_owned(), target.to_owned()))
        }
        Addition::Import { .. } => None,
        Addition::Dependency { package, .. } => {
            Some((format!("{binding}/"), format!("{package}/")))
        }
    };
    let type_target = target.clone();
    let requests = if npm_target {
        if prefix.is_some() {
            phase(format!("Preparing exports for {target:?}..."));
        }
        npm_add_requests(&store, &target, prefix.as_ref())?
    } else if let Some((alias, target)) = prefix {
        let base = url::Url::from_file_path(&config).map_err(|_| "Paths must be absolute")?;
        let map = ImportMap::parse(
            &format!(
                "imports: {{{}: {}}}",
                serde_json::to_string(&alias)?,
                serde_json::to_string(&target)?
            ),
            &base,
        )?;
        let referrer = base.join(".avril-add.js")?;
        let export =
            |request: &str| parse_jsr_request(request).map(|request| request.export_name());
        phase(format!("Preparing exports for {target:?}..."));
        // The prefix's own normalized subpath, found by probing beneath it.
        let probe = export(&format!("{target}x"))?;
        let prefix = &probe["./".len()..probe.len() - 1];
        let mut requests = Vec::new();
        for key in block_on(store.exports(&target))? {
            // Each export the prefix itself or a suffix beneath it reaches under the
            // runtime's import map rules, which reject escapes and encoded separators.
            // Normalization drops one trailing slash, so a key ending in '/' needs another.
            let suffix = key
                .strip_prefix("./")
                .and_then(|key| key.strip_prefix(prefix));
            let mut suffixes = [String::new()].into_iter().chain(
                suffix
                    .into_iter()
                    .flat_map(|suffix| [suffix.to_owned(), format!("{suffix}/")]),
            );
            if let Some(request) = suffixes.find_map(|suffix| {
                let request = map.resolve(&format!("{alias}{suffix}"), &referrer).ok()??;
                (export(&request).ok()? == key).then_some(request)
            }) {
                requests.push(request);
            }
        }
        requests
    } else {
        vec![target]
    };
    let graph = ModuleGraph::open_shared(authority, store.clone());
    graph.set_automatic_types(automatic_types);
    graph.set_typescript_version(avril_lsp::BACKEND_VERSION)?;
    // Warm through the updated config so joint root contexts match what
    // the runtime prepares: registry-referrer contexts would pin different
    // roots than a frozen run looks up once other deps or peers exist.
    let referrer = if npm_target {
        config.to_str().ok_or("Paths must be UTF-8")?.to_owned()
    } else {
        store.options().jsr_registry.to_string()
    };
    let warn_unsupported = Rc::new({
        let warned = RefCell::new(HashSet::<String>::new());
        move |specifier: &str, referrer: &str| {
            if warned.borrow_mut().insert(specifier.to_owned()) {
                use std::io::Write;
                let _ = writeln!(
                    std::io::stderr(),
                    "Warning: skipping unsupported Node.js builtin import {specifier:?} from {referrer:?}; builtin modules remain unsupported at runtime",
                );
            }
        }
    });
    let type_requests = if requests.is_empty() {
        vec![type_target]
    } else {
        requests.clone()
    };
    for request in requests {
        phase(format!("Caching {request:?}..."));
        block_on(graph.prepare_for_add(request, referrer.clone(), warn_unsupported.clone()))?;
    }
    for request in type_requests {
        phase(format!("Caching types for {request:?}..."));
        block_on(graph.prepare_types_for_request(&request, &referrer))?;
    }
    Ok(())
}

/// Cacheable requests for a whole npm package or the export prefix a
/// prefix target names: exact subpaths resolve as a single request,
/// anything else enumerates ESM exports beneath that scope only.
fn npm_add_requests(
    store: &Arc<PackageStore>,
    target: &str,
    prefix: Option<&(String, String)>,
) -> Result<Vec<String>, Box<dyn std::error::Error>> {
    let Some((_, scope)) = prefix else {
        return Ok(vec![target.to_owned()]);
    };
    let resolver = NpmResolver::new(store.clone());
    Ok(block_on(resolver.export_requests(scope))?)
}

fn phase(message: String) {
    use std::io::Write;
    let message = crate::progress::color_action(message, avril_ext_console::colors(true));
    let _ = writeln!(std::io::stderr(), "{message}");
}

fn progress_sink() -> ProgressSink {
    Arc::new(|event: &ProgressEvent| match event {
        ProgressEvent::NpmMetadata { name } => {
            phase(format!("Fetching npm metadata for {name:?}..."));
        }
        ProgressEvent::NpmArchive { name, version } => {
            phase(format!(
                "Downloading npm archive for {:?}...",
                format!("{name}@{version}"),
            ));
        }
        ProgressEvent::NpmMaterialized { name, version } => {
            phase(format!(
                "Materialized npm package {:?}...",
                format!("{name}@{version}"),
            ));
        }
        ProgressEvent::SourceDownload { .. }
        | ProgressEvent::NpmMaterializing { .. }
        | ProgressEvent::NpmResolving => {}
    })
}

fn report(
    change: &Change,
    alias: &str,
    target: &str,
    config: &std::path::Path,
    cwd: &std::path::Path,
) {
    let paint = |stderr: bool, style: &str, text: &str| {
        if avril_ext_console::colors(stderr) {
            format!("\x1b[{style}m{text}\x1b[0m")
        } else {
            text.to_owned()
        }
    };
    let string = |text: &str| paint(false, "32", &serde_json::to_string(text).unwrap());
    let (status, style, previous) = match change {
        Change::Added => ("Added", "1;32", String::new()),
        Change::Updated { previous } => (
            "Updated",
            "1;33",
            format!("{} → ", previous.as_deref().map_or("null".into(), string)),
        ),
        Change::Unchanged => ("Unchanged", "1", String::new()),
    };
    let mut path = String::new();
    // Paths may contain terminal controls, like the strings escaped as JSON above.
    for ch in config
        .strip_prefix(cwd)
        .unwrap_or(config)
        .to_string_lossy()
        .chars()
    {
        if ch.is_control() {
            path.extend(ch.escape_default());
        } else {
            path.push(ch);
        }
    }
    // The status is decoration on stderr; stdout keeps just the resulting mapping.
    eprint!("{} ", paint(true, style, status));
    println!(
        "{}: {previous}{} in {path}",
        paint(false, "1", &serde_json::to_string(alias).unwrap()),
        string(target),
    );
}