use serde::Deserialize;
use std::path::Path;

#[derive(Debug, Clone, Deserialize)]
pub struct ProjectConfig {
    #[serde(default)]
    pub component: Vec<ComponentConfig>,
    pub agent: Option<AgentConfig>,
}

#[derive(Debug, Clone, Deserialize)]
pub struct ComponentConfig {
    pub name: String,
    #[serde(default = "default_path")]
    pub path: String,
    #[serde(default)]
    pub setup: Vec<String>,
    #[serde(default)]
    pub teardown: Vec<String>,
}

#[derive(Debug, Clone, Deserialize)]
pub struct AgentConfig {
    #[serde(default = "default_agent_command")]
    pub command: String,
    #[serde(default)]
    pub args: Vec<String>,
    #[serde(default = "default_agent_prompt")]
    pub prompt: String,
}

fn default_path() -> String {
    ".".to_string()
}

fn default_agent_command() -> String {
    "claude".to_string()
}

fn default_agent_prompt() -> String {
    "Read .story_kit/README.md, then pick up story {{story_id}}".to_string()
}

impl Default for ProjectConfig {
    fn default() -> Self {
        Self {
            component: Vec::new(),
            agent: Some(AgentConfig {
                command: default_agent_command(),
                args: vec![],
                prompt: default_agent_prompt(),
            }),
        }
    }
}

impl ProjectConfig {
    /// Load from `.story_kit/project.toml` relative to the given root.
    /// Falls back to sensible defaults if the file doesn't exist.
    pub fn load(project_root: &Path) -> Result<Self, String> {
        let config_path = project_root.join(".story_kit/project.toml");
        if !config_path.exists() {
            return Ok(Self::default());
        }
        let content =
            std::fs::read_to_string(&config_path).map_err(|e| format!("Read config: {e}"))?;
        toml::from_str(&content).map_err(|e| format!("Parse config: {e}"))
    }

    /// Render template variables in agent args and prompt.
    pub fn render_agent_args(
        &self,
        worktree_path: &str,
        story_id: &str,
    ) -> Option<(String, Vec<String>, String)> {
        let agent = self.agent.as_ref()?;
        let render = |s: &str| {
            s.replace("{{worktree_path}}", worktree_path)
                .replace("{{story_id}}", story_id)
        };
        let command = render(&agent.command);
        let args: Vec<String> = agent.args.iter().map(|a| render(a)).collect();
        let prompt = render(&agent.prompt);
        Some((command, args, prompt))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs;

    #[test]
    fn default_config_when_missing() {
        let tmp = tempfile::tempdir().unwrap();
        let config = ProjectConfig::load(tmp.path()).unwrap();
        assert!(config.agent.is_some());
        assert!(config.component.is_empty());
    }

    #[test]
    fn parse_project_toml() {
        let tmp = tempfile::tempdir().unwrap();
        let sk = tmp.path().join(".story_kit");
        fs::create_dir_all(&sk).unwrap();
        fs::write(
            sk.join("project.toml"),
            r#"
[[component]]
name = "server"
path = "."
setup = ["cargo check"]
teardown = []

[[component]]
name = "frontend"
path = "frontend"
setup = ["pnpm install"]

[agent]
command = "claude"
args = ["--print", "--directory", "{{worktree_path}}"]
prompt = "Pick up story {{story_id}}"
"#,
        )
        .unwrap();

        let config = ProjectConfig::load(tmp.path()).unwrap();
        assert_eq!(config.component.len(), 2);
        assert_eq!(config.component[0].name, "server");
        assert_eq!(config.component[1].setup, vec!["pnpm install"]);

        let agent = config.agent.unwrap();
        assert_eq!(agent.command, "claude");
    }

    #[test]
    fn render_template_vars() {
        let config = ProjectConfig::default();
        let (cmd, args, prompt) = config.render_agent_args("/tmp/wt", "42_foo").unwrap();
        assert_eq!(cmd, "claude");
        assert!(args.is_empty());
        assert!(prompt.contains("42_foo"));
    }
}