use crate::elm;
use crate::reporting::{CompilerError, InterpreterError, Problem, SetupError, TypeError};
use crate::PortableHash;
use deno_core::futures::StreamExt;
use elm_project_utils::ChecksumConstraint;
use os_pipe::dup_stderr;
use serde::{Deserialize, Serialize};
use sqlx::sqlite::SqlitePool;
use sqlx::Row;
use std::cell::RefCell;
use std::fs::{self, canonicalize};
use std::hash::Hasher;
use std::io::{self, Read, Write};
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};
use std::sync::Arc;
use std::time::Instant;
use tokio;
use tracing::{info_span, Instrument};

mod fixtures;

#[derive(Serialize)]
#[serde(tag = "$")]
pub(crate) enum ElmResult<T, E> {
    Ok { a: T },
    Err { a: E },
}

impl<T, E> ElmResult<T, E> {
    fn ok(a: T) -> Self {
        Self::Ok { a }
    }

    fn err(a: E) -> Self {
        Self::Err { a }
    }
}

pub(crate) fn exec(
    file: PathBuf,
    debug: bool,
    function: String,
    input_source: Option<PathBuf>,
    output: Option<PathBuf>,
    verbosity: u64,
    sqlite_path: Option<PathBuf>,
) -> Result<(), Problem> {
    // Our first elm make call is where we build the users program. There is a pretty good chance
    // this won't work.
    elm::make(&file, debug, verbosity)?;

    // Step 2, find the elm.json and elm-stuff directory
    let elm_project_dir =
        elm::find_project_root("elm.json", "./").map_err(CompilerError::MissingElmJson)?;

    let elm_cache_dir = elm_project_dir.join("elm-stuff").join("0.19.1");

    if !elm_cache_dir.is_dir() {
        return Err(CompilerError::MissingElmStuff(elm_cache_dir).into());
    }

    let data = std::fs::read(&file)
        .map_err(|io_err| CompilerError::ReadInputFailed(io_err, file.clone()))?;

    let mut hasher = PortableHash::new();
    hasher.write_all(&data).unwrap();
    // also include the function name in the checksum so users can run multiple functions
    // from the same file but still get caching if the file does not change.
    hasher.write_all(function.as_bytes()).unwrap();
    let source_checksum = hasher.finish();

    // step 2.5 get the module name out of the file.

    let entrypoint = elmi::Global(
        elmi::ModuleNameCanonical {
            package: elmi::PackageName::new("author", "project"),
            module: elm::parse_module_name(&data)?,
        },
        elmi::Name(function.clone()),
    );

    // step 3 find all the filepaths in the elm-stuff/0.19.1/* folder
    let interfaces = elm::load_interfaces(&elm_cache_dir)?;

    // Step 5, check for the desired function
    let span = info_span!("resolved target function");
    let timing_guard = span.enter();
    let (input_type, output_type) = match interfaces.get(&entrypoint.0) {
        Some(interface) => match interface.values.get(&entrypoint.1) {
            Some(annotation) => {
                let elmi::CannonicalAnnotation(_free_vars, tipe) = annotation;

                resolve_function_type(tipe)?
            }
            None => return Err(CompilerError::BadImport(entrypoint).into()),
        },
        None => return Err(CompilerError::MissingModuleTypeInformation(entrypoint.0).into()),
    };
    drop(timing_guard);

    // step 6 create our private project
    let generator_dir = setup_generator_project(verbosity, elm_project_dir.clone())?;

    // step 7 create an Elm fixture file to run our function
    let span = info_span!("create Elm fixture files");
    let timing_guard = span.enter();
    let (gen_module_name, source) = fixtures::scripting::generate(
        source_checksum,
        entrypoint.0.module.clone(),
        entrypoint.1.clone(),
        input_type,
        output_type,
    );

    let mut source_filename = generator_dir.join("src").join(&gen_module_name);
    source_filename.set_extension("elm");

    let span = info_span!("file writes");
    let file_write_timing_guard = span.enter();
    fs::File::create(&source_filename)
        .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, source_filename.clone()))?
        .write_all(source.as_bytes())
        .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, source_filename.clone()))?;
    drop(file_write_timing_guard);
    drop(timing_guard);

    // step 8 compile the fixture
    let mut intermediate_file = generator_dir.join("obj").join(&gen_module_name);
    intermediate_file.set_extension("js");

    let mut command = Command::new("elm");

    command
        .arg("make")
        .arg("--output")
        .arg(&intermediate_file)
        .current_dir(&generator_dir)
        .stdin(Stdio::null())
        .stderr(Stdio::piped());
    if verbosity < 1 {
        command.stdout(Stdio::piped());
    } else {
        let pipe = dup_stderr()
            .map_err(|io_err| CompilerError::ReadInputFailed(io_err, "stdout".into()))?;
        command.stdout(pipe);
    }

    if debug {
        command.arg("--debug");
    }
    command.arg(&source_filename);

    let span = info_span!("elm make fixture file");
    let timing_guard = span.enter();
    match command.output() {
        Ok(output) => {
            if !output.status.success() {
                return Err(CompilerError::FailedBuildingFixture.into());
            }
        }
        Err(_) => {
            return Err(CompilerError::FailedBuildingFixture.into());
        }
    }
    drop(timing_guard);

    // Step 9 fixup the compiled script to run in Deno

    let data = fs::read_to_string(&intermediate_file)
        .map_err(|io_err| CompilerError::ReadInputFailed(io_err, intermediate_file.clone()))?;

    // TODO figure out how to replace multiple substrings in a single pass. One neat trick
    // might be to allocate enough space in our starting buffer to write the new code by
    // having a really large replace block. For example if we are replacing a string
    // `"REPLACE_ME" + "abc" * 2000` we would have over 6k bytes to write out the new code. We
    // will have to do some extra book keeping to make sure the buffer space is big enough
    // for the replacement code.
    let span = info_span!("munge fixture javascript");
    let timing_guard = span.enter();
    let final_script = (|| {
        let mut final_script = data
            .replace("'REPLACE_ME_WITH_JSON_STRINGIFY'", "JSON.stringify(x)")
            .replace(
                "$elm$json$Json$Decode$fail('REPLACE_ME_WITH_BYTES_DECODER');",
                r#" _Json_decodePrim(function(value) {
        return (typeof value === 'object' && value instanceof DataView)
            ? $elm$core$Result$Ok(value)
                : _Json_expecting('a DataView', value);
    });"#,
            )
            .replace(";}(this));", ";}(globalThis));");

        if sqlite_path.is_some() {
            final_script = final_script
                .replace(
                    "var $author$project$Astrid$Query$execute = function (query) {\n\treturn $author$project$Astrid$Query$dummyExecute;\n};",
                    include_str!("fixtures/sql-client-integration.js"),
                )
                .replace(
                    "var $author$project$Astrid$Query$fetch = F3(\n\tfunction (sql, parameters, decoder) {\n\t\treturn $author$project$Astrid$Query$Dummy;\n\t});",
                    "var $author$project$Astrid$Query$fetch = _Query_fetchAll;",
                )
                .replace(
                    "var $author$project$Astrid$Query$fetchOne = F3(\n\tfunction (sql, parameters, decoder) {\n\t\treturn $author$project$Astrid$Query$Dummy;\n\t});",
                    "var $author$project$Astrid$Query$fetchOne = _Query_fetchOne;",
                )
                .replace(
                    "var $author$project$Astrid$Query$map3 = F4(\n\tfunction (f, a, b, c) {\n\t\treturn $author$project$Astrid$Query$Dummy;\n\t});",
                    r#"var $author$project$Astrid$Query$map3 = _Query_map3;"#,
                )
                .replace(
                    "var $author$project$Astrid$Query$map2 = F3(\n\tfunction (f, a, b) {\n\t\treturn $author$project$Astrid$Query$Dummy;\n\t});",
                    r#"var $author$project$Astrid$Query$map2 = _Query_map2;"#,
                )
                .replace(
                    "var $author$project$Astrid$Query$map = F2(\n\tfunction (f, a) {\n\t\treturn $author$project$Astrid$Query$Dummy;\n\t});",
                    r#"var $author$project$Astrid$Query$map = _Query_map1;"#,
                )
                .replace(
                    "var $author$project$Astrid$Query$andThen = F2(\n\tfunction (f, q) {\n\t\treturn $author$project$Astrid$Query$Dummy;\n\t});",
                    r#"var $author$project$Astrid$Query$andThen = _Query_andThen;"#,
                );

            // final_script.replace("var $author$project$Astrid$Query$run = ", "JSON.stringify(x)");
            final_script.push_str("\n\n");
            //final_script.push_str(r#"
            //    Deno.core.print(JSON.stringify(
            //        Deno.core.opSync(
            //            'op_starmelon_batch_queries',
            //            [ [true, "select json_object('id', id, 'foo', foo) from foobar", []]
            //            , [false, "select json_object('id', id, 'foo', foo) from foobar", []]
            //            ]
            //        )
            //    ))
            //"#);
        }

        final_script.push_str("\n\n");
        // I think that when I set this script to be the main module, I am skipping the
        // deno/runtime/js/99_main.js script that sets up a bunch of global variables. If I
        // manually add the timer related code below then setTimeout works again.
        // NB. there are 706 lines of setup code that add a bunch of apis to the global window
        // scope. Figure out if I need to include all of them. For example, starmelon does not need
        // to perform http calls right now, but I eventually want to.
        final_script.push_str("const { setTimeout } = globalThis.__bootstrap.timers;\n");
        final_script.push_str(
            "Deno.core.setMacrotaskCallback(globalThis.__bootstrap.timers.handleTimerMacrotask);\n",
        );
        final_script.push_str("globalThis.setTimeout = setTimeout;\n");

        final_script.push_str(&format!("var worker = Elm.{}.init();\n", &gen_module_name));
        // add a shortcut for invoking the function so I don't have to traverse so many object
        // lookups using the rust v8 API.
        match input_type {
            None => {
                final_script.push_str(
                    "globalThis.runOnInput = function() { worker.ports.onInput.send(null) };\n",
                );
            }
            Some(InputType::Value) => {
                final_script
                    .push_str("globalThis.runOnInput = function(data) { worker.ports.onInput.send(JSON.parse(data)) };\n");
            }
            Some(InputType::String) => {
                final_script.push_str(
                    "globalThis.runOnInput = function(data) { worker.ports.onInput.send(data) };",
                );
            }
            Some(InputType::Bytes) => {
                final_script.push_str(
                    r#"
    globalThis.runOnInput = function(data) {
        const dv = new DataView(data.buffer)
        worker.ports.onInput.send(dv)
    };"#,
                );
            }
        }

        match output_type {
            OutputType::Value => {
                final_script.push_str(
                    r#"
                    worker.ports.onOutput.subscribe(function(output){
                        if (output.ctor === "Ok") {
                            const json = JSON.stringify(output.a);
                            Deno.core.opSync('op_starmelon_string_output', output);
                        } else {
                            Deno.core.opSync('op_starmelon_problem', output.a);
                        }
                    });
                "#,
                );
            }
            OutputType::Bytes => {
                final_script.push_str(
                    r#"
                    // Elm will send a DataView
                    worker.ports.onOutput.subscribe(function(output){
                        if (output.ctor === "Ok") {
                            const ui8 = new Uint8Array(output.a.buffer);
                            Deno.core.opSync('op_starmelon_bytes_output', ui8);
                        } else {
                            Deno.core.opSync('op_starmelon_problem', output.a);
                        }
                    });
                "#,
                );
            }
            OutputType::String | OutputType::Html => {
                final_script.push_str(
                    r#"
                    worker.ports.onOutput.subscribe(function(output){
                        if (output.ctor === "Ok") {
                            Deno.core.opSync('op_starmelon_string_output', output.a);
                        } else {
                            Deno.core.opSync('op_starmelon_problem', output.a);
                        }
                    });
                "#,
                );
            }
        }

        final_script
    })();
    drop(timing_guard);

    let mut final_file = generator_dir.join("bin").join(&gen_module_name);
    final_file.set_extension("js");
    let span = info_span!("file writes");
    let timing_guard = span.enter();
    std::fs::write(&final_file, final_script)
        .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, final_file.clone()))?;
    drop(timing_guard);

    // Create a tokio runtime before registering ops so we can block on futures inside sync ops
    let span = info_span!("create tokio runtime");
    let timing_guard = span.enter();
    let sys = tokio::runtime::Builder::new_current_thread()
        // The default number of additional threads for running blocking FnOnce is 512.
        .max_blocking_threads(1)
        .enable_all()
        .build()
        .unwrap();
    drop(timing_guard);

    // step 10 create a v8 isolate. We need to register a different callback depending on
    // the output type (string, or bytes)

    let span = info_span!("create v8 isolate");
    let timing_guard = span.enter();
    let (mut worker, main_module) = runtime::setup_worker(&final_file.to_string_lossy())
        .map_err(|err| InterpreterError::EventLoop(err))?;
    drop(timing_guard);

    let span = info_span!("register private api");
    let timing_guard = span.enter();
    let mailbox: Arc<RefCell<Option<Result<Vec<u8>, String>>>> = Arc::new(RefCell::new(None));

    let mailbox_clone = Arc::clone(&mailbox);
    worker.js_runtime.register_op(
        "op_starmelon_bytes_output",
        deno_core::op_sync(move |_state, msg: deno_core::ZeroCopyBuf, _: ()| {
            let slice: &[u8] = &msg;
            eprintln!("got message from v8 runtime {:?}", slice.to_owned());
            if let Ok(mut mailbox) = mailbox_clone.try_borrow_mut() {
                mailbox.replace(Ok(slice.to_owned()));
            }
            Ok(())
        }),
    );

    let mailbox_clone = Arc::clone(&mailbox);
    worker.js_runtime.register_op(
        "op_starmelon_string_output",
        deno_core::op_sync(move |_state, msg: String, _: ()| {
            if let Ok(mut mailbox) = mailbox_clone.try_borrow_mut() {
                mailbox.replace(Ok(msg.into_bytes()));
            }
            Ok(())
        }),
    );

    let mailbox_clone = Arc::clone(&mailbox);
    worker.js_runtime.register_op(
        "op_starmelon_problem",
        deno_core::op_sync(move |_state, msg: String, _: ()| {
            eprintln!("got problem from v8 runtime {:?}", &msg);
            if let Ok(mut mailbox) = mailbox_clone.try_borrow_mut() {
                mailbox.replace(Err(msg));
            }
            Ok(())
        }),
    );

    // Step 10.B  setup the sqlite database feature
    let sql_background_thread_handle = if let Some(database_url) = sqlite_path {
        // I want to construct the connection in the initial thread so I can tell if the connection
        // failed
        let db_pool = sys
            .block_on(async { SqlitePool::connect(&database_url.to_string_lossy()).await })
            .unwrap();

        let (worker_mailbox, rx) = std::sync::mpsc::channel::<(
            oneshot::Sender<ElmResult<_, _>>,
            Vec<(bool, String, Vec<String>)>,
        )>();

        let sql_worker_thread = std::thread::spawn(move || {
            let worker = tokio::runtime::Builder::new_current_thread()
                .enable_all()
                .build()
                .unwrap();
            loop {
                if let Ok((response, queries)) = rx.recv() {
                    // I am not sure if I should only work on one database task at a time, or
                    // submit as many takes as possible.  Just spawning the future onto this
                    // exectutor does not seem to work, even though the docs say the thread pool
                    // will poll the future until it completes.
                    let db_pool_clone = db_pool.clone();
                    let span = info_span!("inside sql queries futures");
                    let f = async move {
                        let _start = Instant::now();
                        let db_pool = db_pool_clone;
                        let mut result: Vec<Vec<String>> = vec![];
                        for (fetch_all, sql, _args) in queries {
                            let mut acc = Vec::new();
                            if fetch_all {
                                let mut stream = sqlx::query(&sql).fetch(&db_pool);
                                loop {
                                    match stream.next().await {
                                        None => break,
                                        Some(Ok(row)) => {
                                            match row.try_get::<String, _>(0) {
                                                Ok(s) => acc.push(s),
                                                // TODO set an error flag before returning this one
                                                Err(_) => break,
                                            };
                                        }
                                        Some(Err(err)) => {
                                            eprintln!("got fetch_all sql error {:?}", err);
                                            break;
                                        }
                                    }
                                }
                                result.push(acc);
                            } else {
                                let s = sqlx::query(&sql)
                                    .fetch_one(&db_pool)
                                    .await
                                    .and_then(|row| row.try_get::<String, _>(0))
                                    .unwrap();
                                result.push(vec![s]);
                            }
                        }
                        response.send(ElmResult::ok(result))
                    };

                    // I found it interesting that the runtime of the future from the viewpoint of
                    // tracing was around 230us for a trivial select 2 rows query, but walltime I
                    // measured was around 700us. So polling the future or waiting for file IO is
                    // more expensive than I thought.
                    worker.block_on(f.instrument(span)).unwrap();
                } else {
                    break;
                }
            }
        });
        let worker_mailbox_clone = worker_mailbox.clone();

        worker.js_runtime.register_op(
            "op_starmelon_batch_queries",
            deno_core::op_sync(
                move |_state, queries: Vec<(bool, String, Vec<String>)>, _: ()| {
                    let worker_mailbox = worker_mailbox_clone.clone();
                    let (sender, receiver) =
                        oneshot::channel::<ElmResult<Vec<Vec<String>>, String>>();

                    let span = info_span!("run sql");
                    let timing_guard = span.enter();

                    worker_mailbox.send((sender, queries)).unwrap();
                    let elm_result = receiver.recv().unwrap();

                    drop(timing_guard);

                    Ok(elm_result)
                },
            ),
        );

        Some((worker_mailbox, sql_worker_thread))
    } else {
        None
    };

    worker.js_runtime.sync_ops_cache();
    drop(timing_guard);

    // step 11 marshal the input into the v8 isolate. If we are reading from an
    // input file load that, if we are reading from stdin read that.
    let input = match input_type {
        None => None,
        Some(input_type) => {
            let buffer = match input_source {
                None => {
                    // read from stdin when input_source was not present
                    let mut stdin = io::stdin();
                    let mut buffer = Vec::new();
                    stdin.read_to_end(&mut buffer).unwrap();
                    buffer
                }
                Some(path) => {
                    let buffer = std::fs::read(&path)
                        .map_err(|io_err| CompilerError::ReadInputFailed(io_err, path.clone()))?;

                    buffer
                }
            };
            match input_type {
                InputType::String => {
                    let s = String::from_utf8(buffer).map_err(|_| CompilerError::BadInput)?;

                    Some(ValidatedInput::String(s))
                }
                InputType::Bytes => Some(ValidatedInput::Bytes(buffer)),
                InputType::Value => {
                    let _: serde_json::Value =
                        serde_json::from_slice(&buffer).map_err(|_| CompilerError::BadInput)?;

                    let s = String::from_utf8(buffer).map_err(|_| CompilerError::BadInput)?;

                    Some(ValidatedInput::Value(s))
                }
            }
        }
    };

    let span = info_span!("eval javascript");
    let timing_guard = span.enter();
    sys.block_on(async move { runtime::xyz(worker, main_module, input).await })?;
    drop(timing_guard);

    // step 13 receive the callback
    // If I understood which combination of run_event_loop was required to execute
    // the javascript to completion then we should have something in our mailbox by
    // now. Another way to do this would be with an Arc. This will panic if the
    // mailbox is currently borrowed
    match mailbox.replace(None) {
        Some(Ok(buffer)) => match output {
            None => {
                io::stdout()
                    .write_all(&buffer)
                    .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, "stdout".into()))?;
            }
            Some(filename) => {
                let mut f = fs::File::create(&filename)
                    .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, filename))?;

                f.write_all(&buffer)
                    .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, "stdout".into()))?;
            }
        },
        Some(Err(problem)) => {
            println!("had a problem {}", problem);
        }
        None => println!("nothing in the mailbox"),
    }

    if let Some((tx, thread_handle)) = sql_background_thread_handle {
        drop(tx);
        thread_handle.join().unwrap();
    }

    Ok(())
}

#[derive(Debug, Copy, Clone)]
pub enum InputType {
    Value,
    String,
    Bytes,
}

pub enum ValidatedInput {
    String(String),
    Value(String),
    Bytes(Vec<u8>),
}

#[derive(Debug, Copy, Clone)]
pub enum OutputType {
    Html,
    String,
    Bytes,
    Value,
}

fn resolve_function_type(tipe: &elmi::Type) -> Result<(Option<InputType>, OutputType), TypeError> {
    match tipe {
        elmi::Type::TLambda(a, b) => {
            // We want to check the output types first because this is where we will figure out if
            // there is more than one argument
            let output_type = resolve_output_type(&**b)?;
            let input_type = resolve_input_type(&**a)?;

            Ok((Some(input_type), output_type))
        }
        elmi::Type::TVar(_) => Err(TypeError::CantEvalGeneric),
        elmi::Type::TType(module_name, name, args) if args.is_empty() => {
            // If our function returns a primitive type
            if module_name == "elm/core/String" && name == "String" {
                return Ok((None, OutputType::String));
            }
            if module_name == "elm/bytes/Bytes" && name == "Bytes" {
                return Ok((None, OutputType::String));
            }

            Err(TypeError::CantEvalType(tipe.clone()))
        }
        elmi::Type::TType(module_name, name, _args) => {
            if module_name == "elm/virtual-dom/VirtualDom" && name == "Node" {
                return Ok((None, OutputType::Html));
            }
            Err(TypeError::CantEvalCustomType)
        }
        elmi::Type::TRecord(_, _) => Err(TypeError::CantEvalRecord),
        elmi::Type::TUnit => Err(TypeError::CantEvalUnit),
        elmi::Type::TTuple(_, _, _) => Err(TypeError::CantEvalTuple),
        elmi::Type::TAlias(_, _, _, ref alias) => {
            match &**alias {
                elmi::AliasType::Filled(tipe) => {
                    // I think the recursion is limited to a single step. I have not tested what
                    // the CannonicalAnnotation would look like for a doubly indirect alias, for
                    // example for `view` below
                    // ```elm
                    // type alias Foo = Int
                    // type alias Bar = String
                    //
                    // type alias Zap = Foo -> Bar
                    //
                    // view : Zap
                    // ```
                    resolve_function_type(tipe)
                }
                elmi::AliasType::Holey(_) => return Err(TypeError::CantEvalHoleyAlias),
            }
        }
    }
}

fn resolve_input_type(tipe: &elmi::Type) -> Result<InputType, TypeError> {
    match tipe {
        elmi::Type::TLambda(_, _) => Err(TypeError::EvalRequiresSingleArgument(tipe.clone())),
        elmi::Type::TType(module_name, name, args) if args.is_empty() => {
            if module_name == "elm/core/String" && name == "String" {
                Ok(InputType::String)
            } else if module_name == "elm/bytes/Bytes" && name == "Bytes" {
                Ok(InputType::Bytes)
            } else if module_name == "elm/json/Json.Encode" && name == "Value" {
                Ok(InputType::Value)
            } else {
                Err(TypeError::InputTypeNotSupported(tipe.clone()))
            }
        }
        elmi::Type::TAlias(_, _, _, ref alias) => match &**alias {
            elmi::AliasType::Filled(tipe) => resolve_input_type(tipe),
            elmi::AliasType::Holey(_) => Err(TypeError::CantEvalHoleyAlias),
        },
        _ => Err(TypeError::OutputTypeNotSupported(tipe.clone())),
    }
}

fn resolve_output_type(tipe: &elmi::Type) -> Result<OutputType, TypeError> {
    match tipe {
        elmi::Type::TType(module_name, name, _args) => {
            if module_name == "elm/core/String" && name == "String" {
                Ok(OutputType::String)
            } else if module_name == "elm/bytes/Bytes" && name == "Bytes" {
                Ok(OutputType::Bytes)
            } else if module_name == "elm/json/Json.Encode" && name == "Value" {
                Ok(OutputType::Value)
            } else if module_name == "elm/virtual-dom/VirtualDom" && name == "Node" {
                Ok(OutputType::Html)
            } else {
                Err(TypeError::OutputTypeNotSupported(tipe.clone()))
            }
        }
        elmi::Type::TAlias(_, _, _, ref alias) => match &**alias {
            elmi::AliasType::Filled(tipe) => resolve_output_type(tipe),
            elmi::AliasType::Holey(_) => Err(TypeError::CantEvalHoleyAlias),
        },
        _ => Err(TypeError::OutputTypeNotSupported(tipe.clone())),
    }
}

fn setup_generator_project(verbosity: u64, elm_project_dir: PathBuf) -> Result<PathBuf, Problem> {
    // I added a couple of random bytes to the directory name to reduce the risk of
    // collisions with other programs that also use elm-stuff for their scratch space
    let our_temp_dir = elm_project_dir.join("elm-stuff").join("starmelon-5d9ecc");

    if !our_temp_dir.exists() {
        fs::create_dir(&our_temp_dir)
            .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, our_temp_dir.clone()))?;
    }
    let source_dir = our_temp_dir.join("src");
    let bin_dir = our_temp_dir.join("bin");

    // Rather than attempt to modify the elm.json to use the extra libraries, I will invoke
    // elm install. Because the elm install commands take 500ms for a no-op I decided to
    // use a checksum file when the source elm.json changes

    let elm_json_path = elm_project_dir.join("elm.json");

    let mut constraint =
        ChecksumConstraint::new(&elm_json_path, our_temp_dir.join("elm-json-checksum"))?;

    if !constraint.dirty()? {
        return Ok(our_temp_dir);
    }

    let mut data = fs::read(&elm_json_path)
        .map_err(|io_err| CompilerError::ReadInputFailed(io_err, elm_json_path.clone()))?;

    let mut elm_json = serde_json::from_slice::<ElmApplication>(&mut data)
        .map_err(|err| CompilerError::FailedParseElmJson(err))?;

    let mut new_src_directories = Vec::with_capacity(elm_json.source_directories.len() + 1);
    for dirname in elm_json.source_directories.iter() {
        let dir_path = elm_project_dir.join(dirname);
        let dir = canonicalize(&dir_path)
            .map_err(|io_err| CompilerError::ReadInputFailed(io_err, dir_path.clone()))?;
        new_src_directories.push(dir.to_string_lossy().to_string());
    }

    if !source_dir.exists() {
        std::fs::create_dir(&source_dir)
            .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, source_dir.clone()))?;
    }
    if !bin_dir.exists() {
        std::fs::create_dir(&bin_dir)
            .map_err(|io_err| CompilerError::WriteOutputFailed(io_err, bin_dir.clone()))?;
    }

    new_src_directories.push(
        canonicalize(our_temp_dir.join("src"))
            .map_err(|io_err| CompilerError::ReadInputFailed(io_err, our_temp_dir.join("src")))?
            .to_string_lossy()
            .to_string(),
    );
    eprintln!("before json {:?}", elm_json);
    elm_json.source_directories = new_src_directories;

    eprintln!("modified json {:?}", elm_json);

    let generator_elm_json_path = our_temp_dir.join("elm.json");
    let mut generator_elm_json_file =
        std::fs::File::create(&generator_elm_json_path).map_err(|io_err| {
            CompilerError::WriteOutputFailed(io_err, generator_elm_json_path.clone())
        })?;

    serde_json::to_writer(&mut generator_elm_json_file, &elm_json).map_err(|io_err| {
        CompilerError::WriteElmJsonFailed(io_err, generator_elm_json_path.clone())
    })?;

    elm_install(verbosity, &our_temp_dir, "ThinkAlexandria/elm-html-in-elm")?;
    elm_install(verbosity, &our_temp_dir, "elm/json")?;
    elm_install(verbosity, &our_temp_dir, "elm/bytes")?;

    constraint.update()?;

    Ok(our_temp_dir)
}

#[derive(Debug, Serialize, Deserialize)]
struct ElmApplication {
    #[serde(rename = "source-directories")]
    source_directories: Vec<String>,
    #[serde(flatten)]
    other_fields: serde_json::Value,
}

fn elm_install<P: AsRef<Path>, S: AsRef<str>>(
    verbosity: u64,
    our_temp_dir: P,
    package: S,
) -> Result<(), Problem> {
    let span = info_span!("elm_install");
    let _ = span.enter();
    let mut command = Command::new("elm");

    command
        .arg("install")
        .arg(package.as_ref())
        .stdin(Stdio::piped())
        .current_dir(&our_temp_dir);

    if verbosity < 1 {
        command.stderr(Stdio::null());
        command.stdout(Stdio::null());
    } else {
        let pipe = dup_stderr()
            .map_err(|io_err| CompilerError::ReadInputFailed(io_err, "stdout".into()))?;
        command.stdout(pipe);
        command.stderr(Stdio::piped());
    }

    let mut child = command.spawn().unwrap();

    let child_stdin = child.stdin.as_mut().unwrap();
    child_stdin.write_all(b"y\n").unwrap();
    drop(child_stdin);

    match child.wait() {
        Ok(exit_status) => {
            if !exit_status.success() {
                return Err(SetupError::InstallDependencyFailed.into());
            }
        }
        Err(_) => {
            return Err(SetupError::InstallDependencyFailed.into());
        }
    }

    Ok(())
}

mod runtime {
    use crate::exec::ValidatedInput;
    use crate::reporting::InterpreterError;
    use deno_core::error::{type_error, AnyError};
    use deno_core::futures::FutureExt;
    use deno_core::{resolve_url, FsModuleLoader, ModuleLoader, ModuleSpecifier};
    use deno_runtime::deno_broadcast_channel::InMemoryBroadcastChannel;
    use deno_runtime::permissions::Permissions;
    use deno_runtime::worker::MainWorker;
    use deno_runtime::worker::WorkerOptions;
    use deno_runtime::BootstrapOptions;
    use deno_web::BlobStore;
    use rusty_v8 as v8;

    use std::convert::TryFrom;
    use std::pin::Pin;
    use std::rc::Rc;
    use std::sync::Arc;

    use tracing::{info_span, Instrument};

    fn get_error_class_name(e: &AnyError) -> &'static str {
        deno_runtime::errors::get_error_class_name(e).unwrap_or("Error")
    }

    pub fn setup_worker(path_str: &str) -> Result<(MainWorker, ModuleSpecifier), AnyError> {
        //let module_loader = Rc::new(EmbeddedModuleLoader("void".to_owned()));
        let module_loader = Rc::new(FsModuleLoader);
        let create_web_worker_cb = Arc::new(|_| {
            todo!("Web workers are not supported in the example");
        });

        let options = WorkerOptions {
            bootstrap: BootstrapOptions {
                args: vec![],
                apply_source_maps: false,
                cpu_count: 1,
                debug_flag: false,
                enable_testing_features: false,
                location: None,
                no_color: false,
                runtime_version: "0.29.0".to_string(),
                ts_version: "2.0.0".to_string(),
                unstable: false,
            },
            extensions: vec![],
            unsafely_ignore_certificate_errors: None,
            root_cert_store: None,
            user_agent: "hello_runtime".to_string(),
            seed: None,
            module_loader,
            create_web_worker_cb,
            js_error_create_fn: None,
            maybe_inspector_server: None,
            should_break_on_first_statement: false,
            get_error_class_fn: Some(&get_error_class_name),
            origin_storage_dir: None,
            blob_store: BlobStore::default(),
            broadcast_channel: InMemoryBroadcastChannel::default(),
            shared_array_buffer_store: None,
            compiled_wasm_module_store: None,
        };

        let main_module = deno_core::resolve_path(path_str)?;
        // note: resolve_url is just calling url::Url::parse and mapping the error type
        // let main_module = resolve_url(SPECIFIER)?;
        let permissions = Permissions::allow_all();

        let worker = MainWorker::from_options(main_module.clone(), permissions, options);
        //worker.bootstrap(&options);

        Ok((worker, main_module))
    }

    pub async fn xyz(
        mut worker: MainWorker,
        main_module: ModuleSpecifier,
        input: Option<ValidatedInput>,
    ) -> Result<(), InterpreterError> {
        let wait_for_inspector = false;
        // step 10 load the module into our v8 isolate
        worker
            .execute_main_module(&main_module)
            .instrument(info_span!("execute main module"))
            .await?;
        worker
            .run_event_loop(wait_for_inspector)
            .instrument(info_span!("run v8 event loop"))
            .await?;

        {
            let scope = &mut worker.js_runtime.handle_scope();
            let ctx = scope.get_current_context();
            let global = ctx.global(scope);

            let entrypoint = {
                let x = v8::String::new(scope, "runOnInput")
                    .ok_or(InterpreterError::AllocationFailed)?;
                v8::Local::new(scope, x).into()
            };
            let v8_value = global
                .get(scope, entrypoint)
                .ok_or(InterpreterError::ReferenceError)?;

            // step 12 invoke the function
            let function = v8::Local::<v8::Function>::try_from(v8_value)?;

            let this = v8::undefined(scope).into();

            let span = info_span!("dispatch v8 call");
            let timing_guard = span.enter();
            match input {
                None => {
                    function.call(scope, this, &[]);
                }
                Some(ValidatedInput::String(s)) => {
                    let arg1 = {
                        let x =
                            v8::String::new(scope, &s).ok_or(InterpreterError::AllocationFailed)?;
                        v8::Local::new(scope, x).into()
                    };

                    function.call(scope, this, &[arg1]);
                }
                Some(ValidatedInput::Value(v)) => {
                    let arg1 = {
                        let x =
                            v8::String::new(scope, &v).ok_or(InterpreterError::AllocationFailed)?;
                        v8::Local::new(scope, x).into()
                    };

                    function.call(scope, this, &[arg1]);
                }
                Some(ValidatedInput::Bytes(data)) => {
                    let length = data.len();

                    let y = data.into_boxed_slice();
                    let k = v8::ArrayBuffer::new_backing_store_from_boxed_slice(y).make_shared();
                    let x = v8::ArrayBuffer::with_backing_store(scope, &k);

                    let arg1 = v8::Local::new(scope, x).into();

                    let c = v8::Uint8Array::new(scope, arg1, 0, length).unwrap();

                    let arg2 = v8::Local::new(scope, c).into();

                    function.call(scope, this, &[arg2]);
                }
            }
            drop(timing_guard)
        }

        worker
            .run_event_loop(wait_for_inspector)
            .instrument(info_span!("run v8 event loop"))
            .await?;

        Ok(())
    }

    const SPECIFIER: &str = "file://$deno$/bundle.js";

    struct EmbeddedModuleLoader(String);

    impl ModuleLoader for EmbeddedModuleLoader {
        fn resolve(
            &self,
            specifier: &str,
            _referrer: &str,
            _is_main: bool,
        ) -> Result<ModuleSpecifier, AnyError> {
            if let Ok(module_specifier) = resolve_url(specifier) {
                //if get_source_from_data_url(&module_specifier).is_ok()
                //  || specifier == SPECIFIER
                //{
                return Ok(module_specifier);
                //}
            }
            Err(type_error(
                "Self-contained binaries don't support module loading",
            ))
        }

        fn load(
            &self,
            module_specifier: &ModuleSpecifier,
            _maybe_referrer: Option<ModuleSpecifier>,
            _is_dyn_import: bool,
        ) -> Pin<Box<deno_core::ModuleSourceFuture>> {
            let module_specifier = module_specifier.clone();
            //let is_data_uri = get_source_from_data_url(&module_specifier).ok();
            //let code = if let Some((ref source, _)) = is_data_uri {
            //  source.to_string()
            //} else {
            let code = self.0.to_string();
            //};
            async move {
                //if is_data_uri.is_none() && module_specifier.to_string() != SPECIFIER {
                //  return Err(type_error(
                //    "Self-contained binaries don't support module loading",
                //  ));
                //}

                Ok(deno_core::ModuleSource {
                    code,
                    module_url_specified: module_specifier.to_string(),
                    module_url_found: module_specifier.to_string(),
                })
            }
            .boxed_local()
        }
    }
}