use std::collections::BTreeMap;

use decodal_core::{
    Data, Diagnostic, DiagnosticKind, EmptyLoader, Engine, LoadedSource, SourceLoader, Span,
};
use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn evaluate(source: &str) -> String {
    encode_result(evaluate_inner(source))
}

#[wasm_bindgen(js_name = evaluateProject)]
pub fn evaluate_project(entry: &str, files_json: &str) -> String {
    encode_result(evaluate_project_inner(entry, files_json))
}

fn encode_result(result: Result<String, String>) -> String {
    match result {
        Ok(output) => format!("{{\"ok\":true,\"output\":{}}}", json_string(&output)),
        Err(error) => format!("{{\"ok\":false,\"error\":{}}}", json_string(&error)),
    }
}

fn evaluate_inner(source: &str) -> Result<String, String> {
    let mut engine = Engine::new(EmptyLoader);
    let module = engine
        .add_root_source("playground", "playground", source)
        .map_err(format_diagnostic)?;
    let value = engine.eval_module(module).map_err(format_diagnostic)?;
    let data = engine.materialize(&value).map_err(format_diagnostic)?;
    Ok(format_data(&data, 0))
}

fn evaluate_project_inner(entry: &str, files_json: &str) -> Result<String, String> {
    let raw_files: BTreeMap<String, String> = serde_json::from_str(files_json)
        .map_err(|error| format!("failed to read playground files: {error}"))?;
    let mut files = BTreeMap::new();
    for (path, source) in raw_files {
        let path = normalize_path(&path).ok_or_else(|| format!("invalid file path `{path}`"))?;
        files.insert(path, source);
    }

    let entry = normalize_path(entry).ok_or_else(|| format!("invalid entry path `{entry}`"))?;
    let source = files
        .get(&entry)
        .cloned()
        .ok_or_else(|| format!("entry file `{entry}` was not found"))?;

    let mut engine = Engine::new(VirtualLoader { files });
    let module = engine
        .add_root_source(entry.clone(), entry.clone(), &source)
        .map_err(format_diagnostic)?;
    let value = engine.eval_module(module).map_err(format_diagnostic)?;
    let data = engine.materialize(&value).map_err(format_diagnostic)?;
    Ok(format_data(&data, 0))
}

#[derive(Debug, Clone)]
struct VirtualLoader {
    files: BTreeMap<String, String>,
}

impl SourceLoader for VirtualLoader {
    fn load(
        &mut self,
        current_key: Option<&str>,
        specifier: &str,
    ) -> decodal_core::Result<LoadedSource> {
        let key = resolve_import(current_key, specifier).ok_or_else(|| {
            Diagnostic::new(
                DiagnosticKind::Import,
                Span::default(),
                format!("invalid import path `{specifier}`"),
            )
        })?;
        let source = self.files.get(&key).cloned().ok_or_else(|| {
            Diagnostic::new(
                DiagnosticKind::Import,
                Span::default(),
                format!("import `{specifier}` resolved to `{key}`, but that file does not exist"),
            )
        })?;
        Ok(LoadedSource {
            key: key.clone(),
            name: key,
            source,
        })
    }
}

fn resolve_import(current_key: Option<&str>, specifier: &str) -> Option<String> {
    if specifier.starts_with('/') {
        return normalize_path(specifier);
    }

    let mut base = String::new();
    if let Some(current_key) = current_key {
        if let Some((parent, _file)) = current_key.rsplit_once('/') {
            base.push_str(parent);
            base.push('/');
        }
    }
    base.push_str(specifier);
    normalize_path(&base)
}

fn normalize_path(path: &str) -> Option<String> {
    let mut parts = Vec::new();
    let normalized = path.replace('\\', "/");
    for part in normalized.split('/') {
        match part {
            "" | "." => {}
            ".." => {
                parts.pop()?;
            }
            part => parts.push(part),
        }
    }
    if parts.is_empty() {
        None
    } else {
        Some(parts.join("/"))
    }
}

fn format_diagnostic(diagnostic: decodal_core::Diagnostic) -> String {
    format!(
        "{:?} at {}:{}..{}: {}",
        diagnostic.kind,
        diagnostic.span.source.0,
        diagnostic.span.start,
        diagnostic.span.end,
        diagnostic.message,
    )
}

fn format_data(data: &Data, indent: usize) -> String {
    match data {
        Data::String(value) => json_string(value),
        Data::Int(value) => value.to_string(),
        Data::Float(value) => value.to_string(),
        Data::Bool(value) => value.to_string(),
        Data::Array(items) => {
            if items.is_empty() {
                return String::from("[]");
            }
            let mut out = String::from("[\n");
            for (index, item) in items.iter().enumerate() {
                out.push_str(&" ".repeat(indent + 2));
                out.push_str(&format_data(item, indent + 2));
                if index + 1 != items.len() {
                    out.push(',');
                }
                out.push('\n');
            }
            out.push_str(&" ".repeat(indent));
            out.push(']');
            out
        }
        Data::Object(fields) => {
            if fields.is_empty() {
                return String::from("{}");
            }
            let mut out = String::from("{\n");
            for (index, field) in fields.iter().enumerate() {
                out.push_str(&" ".repeat(indent + 2));
                out.push_str(&json_string(&field.name));
                out.push_str(": ");
                out.push_str(&format_data(&field.value, indent + 2));
                if index + 1 != fields.len() {
                    out.push(',');
                }
                out.push('\n');
            }
            out.push_str(&" ".repeat(indent));
            out.push('}');
            out
        }
    }
}

fn json_string(value: &str) -> String {
    let mut out = String::from("\"");
    for ch in value.chars() {
        match ch {
            '"' => out.push_str("\\\""),
            '\\' => out.push_str("\\\\"),
            '\n' => out.push_str("\\n"),
            '\r' => out.push_str("\\r"),
            '\t' => out.push_str("\\t"),
            ch if ch.is_control() => {
                use core::fmt::Write;
                let _ = write!(out, "\\u{:04x}", ch as u32);
            }
            ch => out.push(ch),
        }
    }
    out.push('"');
    out
}

#[cfg(test)]
mod tests {
    use super::{evaluate_project_inner, normalize_path, resolve_import};

    #[test]
    fn normalizes_virtual_paths() {
        assert_eq!(
            normalize_path("/schemas/../main.dcdl"),
            Some("main.dcdl".into())
        );
        assert_eq!(normalize_path("../main.dcdl"), None);
    }

    #[test]
    fn resolves_imports_relative_to_current_file() {
        assert_eq!(
            resolve_import(Some("schemas/service.dcdl"), "./types.dcdl"),
            Some("schemas/types.dcdl".into())
        );
    }

    #[test]
    fn evaluates_project_imports() {
        let files = r#"{
            "main.dcdl":"let dep = import \"./schemas/service.dcdl\"; in dep.Service & { port = 9443; }",
            "schemas/service.dcdl":"Service = { name = String default \"api\"; port = Int & > 443 default 8443; }"
        }"#;
        let output = evaluate_project_inner("main.dcdl", files).unwrap();
        assert!(output.contains("\"port\": 9443"));
    }
}