//! Inference pipeline — orchestrates routing + generation via Sential Engine.
//!
//! 1. Pipeline pre-processes: hashtags, language detection, KB cache lookup
//! 2. Router classifies the query (keyword + hashtag matching)
//! 3. Engine (llama.cpp) generates with or without LoRA adapter
//! 4. Chat history maintained for context

use anyhow::Result;

use crate::config::Config;
use crate::engine::{Engine, KvCacheConfig};
use crate::pipeline::{ConversationTurn, Pipeline, PipelineResult};
use llama_cpp_2::context::params::KvCacheType;

/// Chat message types
#[derive(Debug, Clone)]
pub enum Message {
    User(String),
    Assistant(String),
}

/// Inference engine: routes queries, generates with LoRA adapters.
#[allow(dead_code)]
pub struct InferenceEngine {
    engine: Engine,
    pipeline: Pipeline,
    config: Config,
    active_expert: String,
    conversation: Vec<Message>,
    /// Accumulated pipeline stats
    total_queries: u64,
    total_cache_hits: u64,
}

impl InferenceEngine {
    /// Initialise: load base model into Engine, register adapters, set up pipeline.
    pub fn new(config: Config) -> Result<Self> {
        tracing::info!("Initialising Sential engine with llama.cpp backend");

        // Offload most layers to GPU (20/25 for Qwen3.5-0.8B, leaves headroom for compute buffers on 6 GB VRAM)
        let n_gpu_layers: u32 = 20;
        let n_ctx: u32 = config.max_seq_len as u32;

        // Build KV-cache config from Config
        let kv_config = KvCacheConfig {
            cache_type_k: parse_cache_type(&config.kv_cache_type_k),
            cache_type_v: parse_cache_type(&config.kv_cache_type_v),
            offload_kqv: config.kv_offload_kqv,
            defrag_thold: config.kv_defrag_thold,
        };

        // Initialise Rust-native engine with KV-cache optimizations
        let engine =
            Engine::new_with_kv_config(&config.base_model_path, n_gpu_layers, n_ctx, kv_config)?;

        // Register all LoRA adapters
        for expert in &config.experts {
            if let Some(adapter_file) = &expert.adapter_file {
                // Support both .gguf (new) and .safetensors (legacy) extensions
                let gguf_path = if adapter_file.ends_with(".gguf") {
                    config.adapters_dir.join(adapter_file)
                } else {
                    let stem = adapter_file.trim_end_matches(".safetensors");
                    config.adapters_dir.join(format!("{stem}.gguf"))
                };

                if !gguf_path.exists() {
                    tracing::warn!(
                        "Adapter GGUF not found: {}. Skipping expert '{}'.",
                        gguf_path.display(),
                        expert.name,
                    );
                    continue;
                }

                let scale: f32 = 1.0; // Standard LoRA scale
                engine.register_adapter(&expert.name, &gguf_path, scale)?;
                tracing::info!(
                    "  Registered adapter '{}' -> {}",
                    expert.name,
                    gguf_path.display()
                );
            }
        }

        // Initialise pipeline (with KB cache)
        let kb_path = config.kb_path.clone();
        let pipeline = Pipeline::new(config.clone(), kb_path)?;
        tracing::info!(
            "Pipeline initialised: KB entries={}, translate={}, cache={}",
            pipeline.kb_len(),
            true,
            pipeline.has_kb(),
        );

        Ok(Self {
            engine,
            pipeline,
            active_expert: "general".to_string(),
            conversation: Vec::new(),
            config,
            total_queries: 0,
            total_cache_hits: 0,
        })
    }

    /// Process a user query (auto-route).
    pub fn process_query(&mut self, query: &str) -> Result<String> {
        self.process_query_with_expert(query, None)
    }

    /// Process a query with an optional expert override.
    pub fn process_query_with_expert(
        &mut self,
        query: &str,
        expert_override: Option<&str>,
    ) -> Result<String> {
        self.total_queries += 1;
        tracing::info!("Processing query through pipeline...");

        // Run the full pipeline (preprocess → KB lookup → route → generate)
        let history: Vec<ConversationTurn> = self.build_conversation_turns();
        let result: PipelineResult =
            self.pipeline
                .run(query, &mut self.engine, expert_override, &history)?;

        // Track cache hits
        if result.from_cache {
            self.total_cache_hits += 1;
        }

        // Log timing
        tracing::info!(
            "Pipeline timing: hash={}µs tr={}µs kb={}µs route={}µs gen={}ms total={}ms | cache={} | expert={}",
            result.timing.hashtag_ms * 1000,
            result.timing.translate_ms * 1000,
            result.timing.kb_lookup_ms * 1000,
            result.timing.routing_ms * 1000,
            result.timing.generation_ms,
            result.timing.total_ms,
            if result.from_cache { "HIT" } else { "MISS" },
            result.expert,
        );

        // Update conversation history
        self.conversation.push(Message::User(query.to_string()));
        self.conversation
            .push(Message::Assistant(result.response.clone()));
        self.active_expert = result.expert.clone();

        tracing::info!("Response ready ({} chars)", result.response.len());
        Ok(result.response)
    }

    /// Convert conversation Message pairs into ConversationTurn slices for the pipeline.
    fn build_conversation_turns(&self) -> Vec<ConversationTurn> {
        let mut turns = Vec::new();
        let mut i = 0;
        while i + 1 < self.conversation.len() {
            if let (Message::User(user), Message::Assistant(assistant)) =
                (&self.conversation[i], &self.conversation[i + 1])
            {
                turns.push(ConversationTurn {
                    user: user.clone(),
                    assistant: assistant.clone(),
                });
            }
            i += 2;
        }
        turns
    }

    /// Reset conversation.
    pub fn reset(&mut self) {
        self.conversation.clear();
        self.active_expert = "general".to_string();
        let _ = self.engine.remove_adapter();
    }

    pub fn active_expert(&self) -> &str {
        &self.active_expert
    }

    pub fn stats(&self) -> serde_json::Value {
        serde_json::json!({
            "active_expert": self.active_expert,
            "conversation_length": self.conversation.len(),
            "gpu_active": self.engine.is_gpu_active(),
            "pipeline": {
                "total_queries": self.total_queries,
                "cache_hits": self.total_cache_hits,
                "cache_hit_rate": if self.total_queries > 0 {
                    format!("{:.1}%", 100.0 * self.total_cache_hits as f64 / self.total_queries as f64)
                } else {
                    "0%".to_string()
                },
                "kb_entries": self.pipeline.kb_len(),
            },
            "engine_stats": {
                "total_prompts": self.engine.stats().total_prompts,
                "total_tokens": self.engine.stats().total_tokens_generated,
                "avg_tokens_per_second": self.engine.stats().avg_tokens_per_second,
            }
        })
    }

    /// Get KV-cache configuration summary
    #[allow(dead_code)]
    pub fn kv_cache_info(&self) -> String {
        format!(
            "KV-cache: K={} V={} offload_kqv={} defrag={:.1}",
            self.config.kv_cache_type_k,
            self.config.kv_cache_type_v,
            self.config.kv_offload_kqv,
            self.config.kv_defrag_thold,
        )
    }

    /// Get pipeline info for display
    pub fn pipeline_info(&self) -> String {
        format!(
            "Pipeline: KB={} entries, Cache hits={}/{}, Hashtag extractor=on, Translator=on",
            self.pipeline.kb_len(),
            self.total_cache_hits,
            self.total_queries,
        )
    }
}

/// Parse KV-cache type string to KvCacheType enum.
fn parse_cache_type(s: &str) -> KvCacheType {
    match s.to_lowercase().as_str() {
        "q4_0" => KvCacheType::Q4_0,
        "q4_1" => KvCacheType::Q4_1,
        "q5_0" => KvCacheType::Q5_0,
        "q5_1" => KvCacheType::Q5_1,
        "q8_0" => KvCacheType::Q8_0,
        "q8_1" => KvCacheType::Q8_1,
        "q2_k" => KvCacheType::Q2_K,
        "q3_k" => KvCacheType::Q3_K,
        "q4_k" => KvCacheType::Q4_K,
        "q5_k" => KvCacheType::Q5_K,
        "q6_k" => KvCacheType::Q6_K,
        "iq4_nl" => KvCacheType::IQ4_NL,
        "f16" => KvCacheType::F16,
        "f32" => KvCacheType::F32,
        _ => {
            tracing::warn!("Unknown KV-cache type '{s}', falling back to Q4_0");
            KvCacheType::Q4_0
        }
    }
}