use crate::using::errors::UsingError;
use crate::using::policy::UsingPolicy;
use crate::using::spec::{PackageKind, UsingPackage};
use std::collections::HashMap;

/// Populate using context vectors from nyash.toml (if present).
/// Keeps behavior aligned with existing runner pipeline:
///  - Adds [using.paths] entries to `using_paths`
///  - Flattens [modules] into (name, path) pairs appended to `pending_modules`
///  - Reads optional [aliases] table (k -> v)
pub fn populate_from_toml(
    using_paths: &mut Vec<String>,
    pending_modules: &mut Vec<(String, String)>,
    aliases: &mut HashMap<String, String>,
    packages: &mut HashMap<String, UsingPackage>,
) -> Result<UsingPolicy, UsingError> {
    let mut policy = UsingPolicy::default();
    // Prefer CWD nyash.toml; if missing, honor NYASH_ROOT/nyash.toml for tools that run from subdirs
    let (text, toml_path) = {
        let path = std::path::Path::new("nyash.toml");
        if path.exists() {
            (
                std::fs::read_to_string(path)
                    .map_err(|e| UsingError::ReadToml(e.to_string()))?,
                path.to_path_buf(),
            )
        } else if let Ok(root) = std::env::var("NYASH_ROOT") {
            let alt = std::path::Path::new(&root).join("nyash.toml");
            if alt.exists() {
                (
                    std::fs::read_to_string(&alt)
                        .map_err(|e| UsingError::ReadToml(e.to_string()))?,
                    alt,
                )
            } else {
                return Ok(policy);
            }
        } else {
            return Ok(policy);
        }
    };
    let doc = toml::from_str::<toml::Value>(&text)
        .map_err(|e| UsingError::ParseToml(e.to_string()))?;
    let toml_dir = toml_path
        .parent()
        .map(|p| p.to_path_buf())
        .unwrap_or_else(|| std::path::PathBuf::from("."));

    // [modules] table flatten: supports nested namespaces (a.b.c = "path")
    if let Some(mods) = doc.get("modules").and_then(|v| v.as_table()) {
        fn visit(prefix: &str, tbl: &toml::value::Table, out: &mut Vec<(String, String)>) {
            for (k, v) in tbl.iter() {
                let name = if prefix.is_empty() { k.to_string() } else { format!("{}.{}", prefix, k) };
                if let Some(s) = v.as_str() {
                    out.push((name, s.to_string()));
                } else if let Some(t) = v.as_table() {
                    visit(&name, t, out);
                }
            }
        }
        visit("", mods, pending_modules);
        if let Some(workspace_tbl) = mods.get("workspace").and_then(|v| v.as_table()) {
            load_workspace_modules(&toml_dir, workspace_tbl, pending_modules, aliases)?;
        }
    }

    // [using.paths] array
    if let Some(using_tbl) = doc.get("using").and_then(|v| v.as_table()) {
        // paths
        if let Some(paths_arr) = using_tbl.get("paths").and_then(|v| v.as_array()) {
            for p in paths_arr {
                if let Some(s) = p.as_str() {
                    let s = s.trim();
                    if !s.is_empty() {
                        using_paths.push(s.to_string());
                        policy.search_paths.push(s.to_string());
                    }
                }
            }
        }
        // aliases
        if let Some(alias_tbl) = using_tbl.get("aliases").and_then(|v| v.as_table()) {
            for (k, v) in alias_tbl.iter() {
                if let Some(target) = v.as_str() {
                    aliases.insert(k.to_string(), target.to_string());
                }
            }
        }
        // named packages: any subtable not paths/aliases is a package
        for (k, v) in using_tbl.iter() {
            if k == "paths" || k == "aliases" { continue; }
            if let Some(tbl) = v.as_table() {
                let kind = tbl.get("kind").and_then(|x| x.as_str()).map(PackageKind::from_str).unwrap_or(PackageKind::Package);
                // path is required
                if let Some(path_s) = tbl.get("path").and_then(|x| x.as_str()) {
                    let path = path_s.to_string();
                    let main = tbl.get("main").and_then(|x| x.as_str()).map(|s| s.to_string());
                    let bid = tbl.get("bid").and_then(|x| x.as_str()).map(|s| s.to_string());
                    packages.insert(k.to_string(), UsingPackage { kind, path, main, bid });
                }
            }
        }
    }

    // legacy top-level [aliases] also accepted (migration)
    if let Some(alias_tbl) = doc.get("aliases").and_then(|v| v.as_table()) {
        for (k, v) in alias_tbl.iter() {
            if let Some(target) = v.as_str() {
                aliases.insert(k.to_string(), target.to_string());
            }
        }
    }

    Ok(policy)
}

fn load_workspace_modules(
    nyash_dir: &std::path::Path,
    workspace_tbl: &toml::value::Table,
    pending_modules: &mut Vec<(String, String)>,
    aliases: &mut HashMap<String, String>,
) -> Result<(), UsingError> {
    let members = workspace_tbl
        .get("members")
        .and_then(|v| v.as_array())
        .ok_or_else(|| UsingError::ParseWorkspaceModule("modules.workspace".into(), "expected members array".into()))?;

    for entry in members {
        let raw_path = entry
            .as_str()
            .ok_or_else(|| UsingError::ParseWorkspaceModule("modules.workspace".into(), "members must be string paths".into()))?;
        let module_path = if std::path::Path::new(raw_path).is_absolute() {
            std::path::PathBuf::from(raw_path)
        } else {
            nyash_dir.join(raw_path)
        };
        let module_dir = module_path
            .parent()
            .map(|p| p.to_path_buf())
            .unwrap_or_else(|| nyash_dir.to_path_buf());
        let module_text = std::fs::read_to_string(&module_path).map_err(|e| {
            UsingError::ReadWorkspaceModule(module_path.to_string_lossy().to_string(), e.to_string())
        })?;
        let module_doc = toml::from_str::<toml::Value>(&module_text).map_err(|e| {
            UsingError::ParseWorkspaceModule(module_path.to_string_lossy().to_string(), e.to_string())
        })?;
        let module_name = module_doc
            .get("module")
            .and_then(|v| v.get("name"))
            .and_then(|v| v.as_str())
            .ok_or_else(|| {
                UsingError::WorkspaceModuleMissingName(module_path.to_string_lossy().to_string())
            })?;
        if let Some(exports_tbl) = module_doc.get("exports").and_then(|v| v.as_table()) {
            for (export_key, export_value) in exports_tbl {
                if let Some(rel_path) = export_value.as_str() {
                    let mut full_name = module_name.to_string();
                    if !export_key.is_empty() {
                        full_name.push('.');
                        full_name.push_str(export_key);
                    }
                    if pending_modules.iter().any(|(name, _)| name == &full_name) {
                        continue;
                    }
                    let resolved_path = module_dir.join(rel_path);
                    let resolved_str = resolved_path
                        .canonicalize()
                        .unwrap_or(resolved_path)
                        .to_string_lossy()
                        .to_string();
                    pending_modules.push((full_name, resolved_str));
                }
            }
        }
        if let Some(alias_tbl) = module_doc.get("aliases").and_then(|v| v.as_table()) {
            for (alias, target) in alias_tbl {
                if let Some(target_str) = target.as_str() {
                    aliases.insert(alias.to_string(), target_str.to_string());
                }
            }
        }
    }

    Ok(())
}