//! Skill index middleware — injects a lightweight skill index into the system prompt.
//!
//! Instead of embedding full skill descriptions (which can consume ~2000 tokens for 70+ skills),
//! this middleware injects only skill IDs and one-line triggers (~600 tokens). The LLM can then
//! call the `skill_load` tool on demand to retrieve full skill details when needed.

use async_trait::async_trait;
use zclaw_types::Result;
use crate::middleware::{AgentMiddleware, MiddlewareContext, MiddlewareDecision};
use crate::tool::{SkillIndexEntry, SkillExecutor};
use std::sync::Arc;

/// Middleware that injects a lightweight skill index into the system prompt.
///
/// The index format is compact:
/// ```text
/// ## Skills (index — use skill_load for details)
/// - finance-tracker: 财务分析、财报解读 [数据分析]
/// - senior-developer: 代码开发、架构设计 [开发工程]
/// ```
pub struct SkillIndexMiddleware {
    /// Pre-built skill index entries, constructed at chain creation time.
    entries: Vec<SkillIndexEntry>,
}

impl SkillIndexMiddleware {
    pub fn new(entries: Vec<SkillIndexEntry>) -> Self {
        Self { entries }
    }

    /// Build index entries from a skill executor that supports listing.
    pub fn from_executor(executor: &Arc<dyn SkillExecutor>) -> Self {
        Self {
            entries: executor.list_skill_index(),
        }
    }
}

#[async_trait]
impl AgentMiddleware for SkillIndexMiddleware {
    fn name(&self) -> &str { "skill_index" }
    fn priority(&self) -> i32 { 200 }

    async fn before_completion(&self, ctx: &mut MiddlewareContext) -> Result<MiddlewareDecision> {
        if self.entries.is_empty() {
            return Ok(MiddlewareDecision::Continue);
        }

        let mut index = String::from("\n\n## Skills (index — call skill_load for details)\n\n");
        for entry in &self.entries {
            let triggers = if entry.triggers.is_empty() {
                String::new()
            } else {
                format!(" — {}", entry.triggers.join(", "))
            };
            index.push_str(&format!("- **{}**: {}{}\n", entry.id, entry.description, triggers));
        }

        ctx.system_prompt.push_str(&index);
        Ok(MiddlewareDecision::Continue)
    }
}