use std::os::unix::fs;
use std::path::PathBuf;

use cliclack::{confirm, input, log, note};

use crate::{
    config::types::ScriptEntry,
    error::AppError,
    services::{path_service::CollisionResult, ServiceStore},
    shim::template::write_shim,
};

pub fn run(store: &ServiceStore) -> Result<(), AppError> {
    let config = store.config.load()?;

    // ── 1. Path to the original script ────────────────────────────────────────
    let source_path: String = input("Path to the script")
        .placeholder("~/dotfiles/git/git-config.py")
        .validate(|raw: &String| {
            let expanded = expand_tilde(raw.trim());
            if !expanded.exists() {
                Err("File not found.")
            } else if !expanded.is_file() {
                Err("Path is a directory, not a file.")
            } else {
                Ok(())
            }
        })
        .interact()?;

    let source_path = expand_tilde(source_path.trim());

    // ── 2. Name (shim name, no extension) ─────────────────────────────────────
    // Default to the file stem of the source, without extension
    let default_name = source_path
        .file_stem()
        .and_then(|s| s.to_str())
        .unwrap_or("")
        .to_string();

    let name: String = input("Script name (this becomes the command you call)")
        .placeholder(&default_name)
        .default_input(&default_name)
        .validate(|n: &String| {
            let n = n.trim();
            if n.is_empty() {
                return Err("Name cannot be empty.");
            }
            if n.contains(' ') {
                return Err("Name cannot contain spaces.");
            }
            if n.contains('/') {
                return Err("Name cannot contain slashes.");
            }
            Ok(())
        })
        .interact()?;

    let name = name.trim().to_string();

    // Guard: already registered under this name
    if store.registry.name_exists(&name)? {
        log::error(format!("A script named '{name}' is already registered."))?;
        return Err(AppError::Cancelled);
    }

    // Guard: collision with existing $PATH executable
    match store.path.check_collision(&name) {
        CollisionResult::Collision { path } => {
            note(
                "Name conflict",
                format!(
                    "'{name}' already exists at {}\nYour shim will shadow it on $PATH.",
                    path.display()
                ),
            )?;
            let proceed = confirm("Continue anyway?").interact()?;
            if !proceed {
                return Err(AppError::Cancelled);
            }
        }
        CollisionResult::Clear => {}
    }

    // ── 3. Description ─────────────────────────────────────────────────────────
    let description: String = input("Description")
        .placeholder("One-line summary shown in --help and the script list")
        .validate(|d: &String| {
            if d.trim().is_empty() {
                Err("Description cannot be empty.")
            } else {
                Ok(())
            }
        })
        .interact()?;

    // ── 4. Usage line ──────────────────────────────────────────────────────────
    let default_usage = format!("{name} [options]");
    let usage: String = input("Usage line")
        .placeholder(&default_usage)
        .default_input(&default_usage)
        .interact()?;

    // ── 5. Tags (optional) ─────────────────────────────────────────────────────
    let tags_raw: String = input("Tags (optional, comma-separated)")
        .placeholder("git, config, tools")
        .required(false)
        .interact()?;

    let tags: Vec<String> = tags_raw
        .split(',')
        .map(|t| t.trim().to_string())
        .filter(|t| !t.is_empty())
        .collect();

    // ── 6. Confirm ─────────────────────────────────────────────────────────────
    let symlink_path = store.config.scripts_dir.join(&name);
    let shim_path = config.bin_dir.join(&name);

    note(
        "Summary",
        format!(
            "Name:        {name}\n\
             Source:      {source}\n\
             Symlink:     {symlink}\n\
             Shim:        {shim}\n\
             Description: {description}\n\
             Usage:       {usage}\n\
             Tags:        {tags}",
            source = source_path.display(),
            symlink = symlink_path.display(),
            shim = shim_path.display(),
            tags = if tags.is_empty() { "none".to_string() } else { tags.join(", ") },
        ),
    )?;

    let confirmed = confirm("Register this script?").interact()?;
    if !confirmed {
        return Err(AppError::Cancelled);
    }

    // ── 7. Write symlink, shim, registry entry ─────────────────────────────────

    // Ensure bin_dir exists
    std::fs::create_dir_all(&config.bin_dir)?;

    // Create symlink: scripts_dir/name → source_path
    if symlink_path.exists() || symlink_path.is_symlink() {
        std::fs::remove_file(&symlink_path)?;
    }
    fs::symlink(&source_path, &symlink_path)?;

    // Write the bash shim
    write_shim(
        &shim_path,
        &symlink_path,
        &name,
        &description,
        &usage,
        &config.default_shell,
    )?;

    // Persist to registry
    store.registry.add(ScriptEntry {
        name: name.clone(),
        source_path,
        symlink_path,
        shim_path,
        description,
        usage,
        tags,
    })?;

    log::success(format!("'{name}' registered. You can now call it directly."))?;

    Ok(())
}

/// Expands a leading `~/` to the user's home directory.
/// Returns the path unchanged if it doesn't start with `~/`.
fn expand_tilde(raw: &str) -> PathBuf {
    if let Some(rest) = raw.strip_prefix("~/") {
        if let Ok(home) = std::env::var("HOME") {
            return PathBuf::from(home).join(rest);
        }
    }
    PathBuf::from(raw)
}