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

/// Return the Composer home directory, respecting `COMPOSER_HOME` and
/// falling back to the platform default (`~/.config/composer` on Unix,
/// `%APPDATA%/Composer` on Windows).
pub(crate) fn composer_home() -> String {
    if let Ok(home) = std::env::var("COMPOSER_HOME") {
        return home;
    }

    #[cfg(target_os = "windows")]
    {
        std::env::var("APPDATA")
            .map(|p| format!("{p}/Composer"))
            .unwrap_or_else(|_| "C:/ProgramData/ComposerSetup/bin".to_string())
    }

    #[cfg(not(target_os = "windows"))]
    {
        if let Ok(xdg) = std::env::var("XDG_CONFIG_HOME") {
            format!("{xdg}/composer")
        } else {
            std::env::var("HOME")
                .map(|h| format!("{h}/.config/composer"))
                .unwrap_or_else(|_| "/tmp/composer".to_string())
        }
    }
}

/// Build the working directory path, preferring `--working-dir` over `cwd`.
pub(crate) fn working_dir(cli: &super::Cli) -> anyhow::Result<PathBuf> {
    match &cli.working_dir {
        Some(d) => Ok(PathBuf::from(d)),
        None => Ok(std::env::current_dir()?),
    }
}

/// Read a JSON file as `serde_json::Value`.
/// If the file does not exist, return a default skeleton:
/// `{"config": {}}` for global files, `{}` for local.
pub(crate) fn read_json_file(path: &Path, is_global: bool) -> anyhow::Result<serde_json::Value> {
    if !path.exists() {
        if is_global {
            return Ok(serde_json::json!({"config": {}}));
        }
        return Ok(serde_json::json!({}));
    }
    let content = std::fs::read_to_string(path)?;
    let value: serde_json::Value = serde_json::from_str(&content)
        .map_err(|e| anyhow!("Failed to parse JSON from {}: {}", path.display(), e))?;
    Ok(value)
}

/// Write a `serde_json::Value` back to a file with 4-space indentation + trailing newline.
pub(crate) fn write_json_file(path: &Path, value: &serde_json::Value) -> anyhow::Result<()> {
    if let Some(parent) = path.parent()
        && !parent.as_os_str().is_empty()
    {
        std::fs::create_dir_all(parent)?;
    }
    mozart_core::package::write_to_file(value, path)?;
    Ok(())
}

/// Add a repository entry to the `repositories` array in json.
/// If `append` is true, push to end; otherwise insert at beginning.
/// Removes any existing entry with the same name first.
pub(crate) fn add_repository(
    json: &mut serde_json::Value,
    name: &str,
    config: serde_json::Value,
    append: bool,
) {
    if !json["repositories"].is_array() {
        json["repositories"] = serde_json::json!([]);
    }

    remove_repository(json, name);

    let repos = json["repositories"].as_array_mut().unwrap();
    if append {
        repos.push(config);
    } else {
        repos.insert(0, config);
    }
}

/// Remove a repository entry by name from the `repositories` array.
pub(crate) fn remove_repository(json: &mut serde_json::Value, name: &str) {
    if let Some(repos) = json["repositories"].as_array_mut() {
        repos.retain(|entry| {
            if let Some(entry_name) = entry.get("name").and_then(|n| n.as_str()) {
                entry_name != name
            } else {
                let disabled_key_matches = entry
                    .as_object()
                    .map(|obj| obj.contains_key(name))
                    .unwrap_or(false);
                !disabled_key_matches
            }
        });
    }
}

/// Insert a repository entry before or after a named repository.
/// Returns an error if the target repository is not found.
pub(crate) fn insert_repository(
    json: &mut serde_json::Value,
    name: &str,
    config: serde_json::Value,
    target: &str,
    before: bool,
) -> anyhow::Result<()> {
    if !json["repositories"].is_array() {
        json["repositories"] = serde_json::json!([]);
    }

    remove_repository(json, name);

    let repos = json["repositories"].as_array_mut().unwrap();

    let pos = repos
        .iter()
        .position(|entry| {
            entry.get("name").and_then(|n| n.as_str()) == Some(target)
                || entry
                    .as_object()
                    .map(|obj| obj.contains_key(target))
                    .unwrap_or(false)
        })
        .ok_or_else(|| anyhow!("Repository \"{target}\" not found"))?;

    let insert_pos = if before { pos } else { pos + 1 };
    repos.insert(insert_pos, config);
    Ok(())
}

/// Render a `serde_json::Value` as a human-readable string suitable for
/// single-line display (matching Composer's behaviour).
pub(crate) fn render_value(v: &serde_json::Value) -> String {
    match v {
        serde_json::Value::Null => "null".to_string(),
        serde_json::Value::Bool(b) => if *b { "true" } else { "false" }.to_string(),
        serde_json::Value::Number(n) => n.to_string(),
        serde_json::Value::String(s) => s.clone(),
        serde_json::Value::Array(_) => {
            serde_json::to_string(v).unwrap_or_else(|_| "[]".to_string())
        }
        serde_json::Value::Object(obj) => {
            if obj.is_empty() {
                "{}".to_string()
            } else {
                serde_json::to_string(v).unwrap_or_else(|_| "{}".to_string())
            }
        }
    }
}