zig-core 0.9.0

use std::path::{Path, PathBuf};

use crate::error::ZigError;

/// Return the global workflows directory derived from a given home directory.
pub fn global_workflows_dir_from(home: &Path) -> PathBuf {
    home.join(".zig").join("workflows")
}

/// Return the global workflows directory: `~/.zig/workflows/`.
/// Returns `None` if the HOME environment variable is not set.
pub fn global_workflows_dir() -> Option<PathBuf> {
    std::env::var("HOME")
        .ok()
        .map(|home| global_workflows_dir_from(Path::new(&home)))
}

/// Ensure the global workflows directory exists, creating it if necessary.
pub fn ensure_global_workflows_dir() -> Result<PathBuf, ZigError> {
    let dir = global_workflows_dir()
        .ok_or_else(|| ZigError::Io("HOME environment variable not set".into()))?;
    if !dir.exists() {
        std::fs::create_dir_all(&dir)
            .map_err(|e| ZigError::Io(format!("failed to create {}: {e}", dir.display())))?;
    }
    Ok(dir)
}

// =====================================================================
// Local (project-level) workflow directories.
//
// Layout: `<git-root>/.zig/workflows/` — discovered by walking up from
// the current working directory to the git root, matching the convention
// used by resources and memory.
// =====================================================================

/// Walk up from `start` looking for a `.zig/workflows` directory. Stops at the
/// containing git repository root, or returns the directory in `start` itself
/// if it exists.
pub fn cwd_workflows_dir_from(start: &Path) -> Option<PathBuf> {
    let mut current = start;
    let stop = find_git_root(start);

    loop {
        let candidate = current.join(".zig").join("workflows");
        if candidate.is_dir() {
            return Some(candidate);
        }
        if let Some(ref root) = stop {
            if current == root.as_path() {
                return None;
            }
        }
        match current.parent() {
            Some(p) => current = p,
            None => return None,
        }
    }
}

/// Walk up from the process's current working directory looking for a
/// `.zig/workflows` directory. See [`cwd_workflows_dir_from`].
pub fn cwd_workflows_dir() -> Option<PathBuf> {
    let cwd = std::env::current_dir().ok()?;
    cwd_workflows_dir_from(&cwd)
}

// =====================================================================
// Resource directories.
//
// Layout under the global base directory:
//
//   ~/.zig/
//     resources/
//       _shared/                    files advertised to every workflow
//       <workflow-name>/            files advertised to a single named workflow
//
// Project-local resources live under `<git-root>/.zig/resources/` and are
// discovered by walking up from the current working directory until a git
// root is found (matching the convention used for session storage).
// =====================================================================

/// Return the global resources directory derived from a given home directory.
pub fn global_resources_dir_from(home: &Path) -> PathBuf {
    home.join(".zig").join("resources")
}

/// Return the global resources directory: `~/.zig/resources/`.
/// Returns `None` if the HOME environment variable is not set.
pub fn global_resources_dir() -> Option<PathBuf> {
    std::env::var("HOME")
        .ok()
        .map(|h| global_resources_dir_from(Path::new(&h)))
}

/// Return the per-workflow global resources directory: `~/.zig/resources/<name>/`.
pub fn global_resources_for(workflow: &str) -> Option<PathBuf> {
    global_resources_dir().map(|d| d.join(workflow))
}

/// Return the shared global resources directory: `~/.zig/resources/_shared/`.
///
/// Files placed here are advertised to every workflow regardless of name.
pub fn global_shared_resources_dir() -> Option<PathBuf> {
    global_resources_dir().map(|d| d.join("_shared"))
}

/// Ensure the global resources directory (or a child of it) exists.
pub fn ensure_global_resources_dir(child: Option<&str>) -> Result<PathBuf, ZigError> {
    let mut dir = global_resources_dir()
        .ok_or_else(|| ZigError::Io("HOME environment variable not set".into()))?;
    if let Some(c) = child {
        dir = dir.join(c);
    }
    if !dir.exists() {
        std::fs::create_dir_all(&dir)
            .map_err(|e| ZigError::Io(format!("failed to create {}: {e}", dir.display())))?;
    }
    Ok(dir)
}

/// Walk up from `start` looking for a `.zig/resources` directory. Stops at the
/// containing git repository root (matching `find_git_root`'s discovery
/// boundary), or returns the directory in `start` itself if it exists.
///
/// Returns `None` if no such directory is found before hitting the git root
/// or the filesystem root.
pub fn cwd_resources_dir_from(start: &Path) -> Option<PathBuf> {
    let mut current = start;
    let stop = find_git_root(start);

    loop {
        let candidate = current.join(".zig").join("resources");
        if candidate.is_dir() {
            return Some(candidate);
        }
        if let Some(ref root) = stop {
            if current == root.as_path() {
                return None;
            }
        }
        match current.parent() {
            Some(p) => current = p,
            None => return None,
        }
    }
}

/// Walk up from the process's current working directory looking for a
/// `.zig/resources` directory. See [`cwd_resources_dir_from`].
pub fn cwd_resources_dir() -> Option<PathBuf> {
    let cwd = std::env::current_dir().ok()?;
    cwd_resources_dir_from(&cwd)
}

// =====================================================================
// Memory directories — same tiered layout as resources, under `memory/`.
// =====================================================================

/// Return the global memory directory: `~/.zig/memory/`.
pub fn global_memory_dir() -> Option<PathBuf> {
    std::env::var("HOME")
        .ok()
        .map(|h| Path::new(&h).join(".zig").join("memory"))
}

/// Return the per-workflow global memory directory: `~/.zig/memory/<name>/`.
pub fn global_memory_for(workflow: &str) -> Option<PathBuf> {
    global_memory_dir().map(|d| d.join(workflow))
}

/// Return the shared global memory directory: `~/.zig/memory/_shared/`.
pub fn global_shared_memory_dir() -> Option<PathBuf> {
    global_memory_dir().map(|d| d.join("_shared"))
}

/// Ensure the global memory directory (or a child of it) exists.
pub fn ensure_global_memory_dir(child: Option<&str>) -> Result<PathBuf, ZigError> {
    let mut dir = global_memory_dir()
        .ok_or_else(|| ZigError::Io("HOME environment variable not set".into()))?;
    if let Some(c) = child {
        dir = dir.join(c);
    }
    if !dir.exists() {
        std::fs::create_dir_all(&dir)
            .map_err(|e| ZigError::Io(format!("failed to create {}: {e}", dir.display())))?;
    }
    Ok(dir)
}

/// Walk up from `start` looking for a `.zig/memory` directory. Stops at the
/// containing git repository root, or returns the directory in `start` itself
/// if it exists.
pub fn cwd_memory_dir_from(start: &Path) -> Option<PathBuf> {
    let mut current = start;
    let stop = find_git_root(start);

    loop {
        let candidate = current.join(".zig").join("memory");
        if candidate.is_dir() {
            return Some(candidate);
        }
        if let Some(ref root) = stop {
            if current == root.as_path() {
                return None;
            }
        }
        match current.parent() {
            Some(p) => current = p,
            None => return None,
        }
    }
}

/// Walk up from the process's current working directory looking for a
/// `.zig/memory` directory. See [`cwd_memory_dir_from`].
pub fn cwd_memory_dir() -> Option<PathBuf> {
    let cwd = std::env::current_dir().ok()?;
    cwd_memory_dir_from(&cwd)
}

// =====================================================================
// Example files directory.
// =====================================================================

/// Return the global examples directory: `~/.zig/examples/`.
pub fn global_examples_dir() -> Option<PathBuf> {
    global_base_dir().map(|d| d.join("examples"))
}

/// Ensure the global examples directory exists, creating it if necessary.
pub fn ensure_global_examples_dir() -> Result<PathBuf, ZigError> {
    let dir = global_examples_dir()
        .ok_or_else(|| ZigError::Io("HOME environment variable not set".into()))?;
    if !dir.exists() {
        std::fs::create_dir_all(&dir)
            .map_err(|e| ZigError::Io(format!("failed to create {}: {e}", dir.display())))?;
    }
    Ok(dir)
}

// =====================================================================
// Session storage paths.
//
// Layout mirrors zag (`zag-agent/src/config.rs:183` `resolve_project_dir`):
//
//   ~/.zig/
//     projects/<sanitized-project-path>/logs/
//                                       index.json
//                                       sessions/<id>.jsonl
//     sessions_index.json     (global cross-project index)
//
// Keeping this layout byte-for-byte aligned with `~/.zag/` is intentional
// so future changes to zag's session/listen architecture can be mirrored
// into zig with minimal churn.
// =====================================================================

/// Return the global zig base directory: `~/.zig/`.
pub fn global_base_dir() -> Option<PathBuf> {
    std::env::var("HOME")
        .ok()
        .map(|h| Path::new(&h).join(".zig"))
}

/// Resolve the user's home directory from the environment.
///
/// Checks `HOME` first (the Unix convention zig workflows are written
/// against), then falls back to `USERPROFILE` on Windows where `HOME`
/// is typically not set. Returns `None` if neither variable is set.
pub(crate) fn env_home() -> Option<String> {
    std::env::var("HOME")
        .ok()
        .or_else(|| std::env::var("USERPROFILE").ok())
}

/// Expand `~/` and `$HOME` / `${HOME}` in a path string.
///
/// Handles three forms:
/// - Leading `~/` → replaced with the home directory
/// - `~` alone    → replaced with the home directory
/// - `$HOME` or `${HOME}` anywhere in the string → replaced with the home dir
///
/// The home directory is resolved from `HOME`, falling back to `USERPROFILE`
/// on Windows. Other environment variables and absolute paths are returned
/// unchanged. Returns the input unchanged if no home variable is set.
pub fn expand_path(path: &str) -> String {
    let home = match env_home() {
        Some(h) => h,
        None => return path.to_string(),
    };

    let s = if path == "~" {
        home.clone()
    } else if let Some(rest) = path.strip_prefix("~/") {
        format!("{home}/{rest}")
    } else {
        path.to_string()
    };

    s.replace("${HOME}", &home).replace("$HOME", &home)
}

/// Replace the home directory prefix with `~` for display purposes.
///
/// This is the inverse of [`expand_path`]: given an absolute path like
/// `/Users/alice/.zig/workflows/foo.zwf`, returns `~/.zig/workflows/foo.zwf`.
/// Paths that don't start with the home directory are returned unchanged.
pub fn collapse_home(path: &str) -> String {
    let home = match env_home() {
        Some(h) => h,
        None => return path.to_string(),
    };

    if path == home {
        "~".to_string()
    } else if let Some(rest) = path.strip_prefix(&format!("{home}/")) {
        format!("~/{rest}")
    } else {
        path.to_string()
    }
}

/// Sanitize an absolute path into a directory name.
///
/// Strips leading `/` and replaces remaining `/` with `-`. Mirrors zag's
/// `Config::sanitize_path` (`zag-agent/src/config.rs:179`).
pub fn sanitize_project_path(path: &str) -> String {
    path.trim_start_matches('/').replace('/', "-")
}

/// Find the git repository root containing `start`, walking parents.
fn find_git_root(start: &Path) -> Option<PathBuf> {
    let mut current = start;
    loop {
        if current.join(".git").exists() {
            return Some(current.to_path_buf());
        }
        current = current.parent()?;
    }
}

/// Resolve the project directory for session storage.
///
/// Mirrors zag's `Config::resolve_project_dir` (`zag-agent/src/config.rs:188`):
///   1. If `root` is provided, sanitize it directly.
///   2. Otherwise locate the git repository root containing `cwd`.
///   3. Otherwise fall back to the global base directory (no project subdir).
pub fn project_dir(root: Option<&str>) -> Option<PathBuf> {
    let base = global_base_dir()?;
    if let Some(r) = root {
        return Some(base.join("projects").join(sanitize_project_path(r)));
    }
    let cwd = std::env::current_dir().ok()?;
    if let Some(git_root) = find_git_root(&cwd) {
        let sanitized = sanitize_project_path(&git_root.to_string_lossy());
        return Some(base.join("projects").join(sanitized));
    }
    Some(base)
}

/// Return the per-project logs directory: `<project>/logs/`.
pub fn project_logs_dir(root: Option<&str>) -> Option<PathBuf> {
    project_dir(root).map(|p| p.join("logs"))
}

/// Return the per-project sessions directory: `<project>/logs/sessions/`.
pub fn project_sessions_dir(root: Option<&str>) -> Option<PathBuf> {
    project_logs_dir(root).map(|p| p.join("sessions"))
}

/// Return the per-project index file: `<project>/logs/index.json`.
pub fn project_index_path(root: Option<&str>) -> Option<PathBuf> {
    project_logs_dir(root).map(|p| p.join("index.json"))
}

/// Return the global cross-project session index: `~/.zig/sessions_index.json`.
pub fn global_sessions_index_path() -> Option<PathBuf> {
    global_base_dir().map(|p| p.join("sessions_index.json"))
}

/// Ensure the per-project sessions directory exists, creating it if needed.
pub fn ensure_project_sessions_dir(root: Option<&str>) -> Result<PathBuf, ZigError> {
    let dir = project_sessions_dir(root)
        .ok_or_else(|| ZigError::Io("HOME environment variable not set".into()))?;
    if !dir.exists() {
        std::fs::create_dir_all(&dir)
            .map_err(|e| ZigError::Io(format!("failed to create {}: {e}", dir.display())))?;
    }
    Ok(dir)
}

#[cfg(test)]
#[path = "paths_tests.rs"]
mod tests;