//! Synthesis Handler (Phase 5)
//!
//! HTTP endpoints for knowledge synthesis features:
//! - Entity linking
//! - Inference
//! - Reasoning
//! - Summarization

use actix_web::{web, HttpRequest, HttpResponse};
use serde::{Deserialize, Serialize};
use tracing::{debug, error, info};

use crate::http_server::AppState;
use crate::query::{
    EntityLinker, MentionLink, AliasSuggestion, MergeSuggestion, CoreferenceCluster,
    InferenceEngine, InferenceRule, InferredFact, ReasoningPath, TransitiveClosure,
    QueryReasoner, SubQuery, Constraint, QuestionType, ReasonedAnswer,
    Summarizer, SummarizationStrategy, Summary, KeyFact,
};

/// Request to link entities
#[derive(Debug, Deserialize)]
pub struct LinkEntitiesRequest {
    /// Project ID
    pub project: String,
    /// Text to link entities in
    pub text: String,
}

/// Response from entity linking
#[derive(Debug, Serialize)]
pub struct LinkEntitiesResponse {
    /// Linked mentions
    pub links: Vec<MentionLink>,
    /// Unlinked mention texts
    pub unlinked: Vec<String>,
    /// Total mentions found
    pub total_mentions: usize,
    /// Link success rate
    pub link_rate: f32,
    /// Processing time in ms
    pub process_time_ms: u128,
}

/// Request to detect aliases
#[derive(Debug, Deserialize)]
pub struct DetectAliasesRequest {
    /// Project ID
    pub project: String,
    /// Entity ID
    pub entity_id: String,
    /// Entity name (canonical)
    pub entity_name: String,
    /// Text samples to analyze
    pub text_samples: Vec<String>,
}

/// Response from alias detection
#[derive(Debug, Serialize)]
pub struct DetectAliasesResponse {
    pub entity_id: String,
    pub entity_name: String,
    pub aliases: Vec<AliasSuggestion>,
    pub alias_count: usize,
    pub process_time_ms: u128,
}

/// Request to suggest merges
#[derive(Debug, Deserialize)]
pub struct SuggestMergesRequest {
    /// Project ID
    pub project: String,
    /// Minimum similarity threshold (0.0-1.0, default 0.8)
    #[serde(default = "default_merge_threshold")]
    pub similarity_threshold: f32,
}

/// Response from merge suggestion
#[derive(Debug, Serialize)]
pub struct SuggestMergesResponse {
    pub project: String,
    pub suggestions: Vec<MergeSuggestion>,
    pub suggestion_count: usize,
    pub process_time_ms: u128,
}

/// Request to detect coreferences
#[derive(Debug, Deserialize)]
pub struct DetectCoreferencesRequest {
    /// Project ID
    pub project: String,
    /// Text samples
    pub texts: Vec<String>,
}

/// Response from coreference detection
#[derive(Debug, Serialize)]
pub struct DetectCoreferencesResponse {
    pub project: String,
    pub clusters: Vec<CoreferenceCluster>,
    pub cluster_count: usize,
    pub total_mentions: usize,
    pub process_time_ms: u128,
}

fn default_merge_threshold() -> f32 { 0.8 }

/// POST /memory/synthesis/link-entities - Link mentions to entities
pub async fn link_entities_handler(
    req: HttpRequest,
    body: web::Json<LinkEntitiesRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    // Validate JWT + rate limit
    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 100
    ) {
        return response;
    }

    // Validate input
    if body.text.is_empty() || body.text.len() > 10000 {
        return crate::handlers::response_builder::bad_request(
            "Text must be 1-10000 characters"
        );
    }

    debug!("Entity linking: project='{}', text_len={}", body.project, body.text.len());

    // Create entity linker
    let linker = EntityLinker::new(state.pool.clone());

    // Link entities
    let (links, unlinked) = match linker.link_mentions(&body.text, &body.project).await {
        Ok((links, unlinked)) => (links, unlinked),
        Err(e) => {
            error!("Entity linking failed: {}", e);
            return crate::handlers::response_builder::internal_error(
                &format!("Linking failed: {}", e)
            );
        }
    };

    let total = links.len() + unlinked.len();
    let link_rate = if total > 0 {
        (links.len() as f32 / total as f32)
    } else {
        0.0
    };

    let elapsed = start_time.elapsed().as_millis();
    info!("Entity linking completed: {}/{} linked in {}ms", links.len(), total, elapsed);

    let response = LinkEntitiesResponse {
        links,
        unlinked,
        total_mentions: total,
        link_rate,
        process_time_ms: elapsed,
    };

    crate::handlers::response_builder::success_response(response)
}

/// POST /memory/synthesis/detect-aliases - Detect aliases for entity
pub async fn detect_aliases_handler(
    req: HttpRequest,
    body: web::Json<DetectAliasesRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    // Validate JWT + rate limit
    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 100
    ) {
        return response;
    }

    // Validate input
    if body.entity_id.is_empty() || body.entity_name.is_empty() {
        return crate::handlers::response_builder::bad_request(
            "entity_id and entity_name required"
        );
    }

    if body.text_samples.is_empty() {
        return crate::handlers::response_builder::bad_request(
            "text_samples cannot be empty"
        );
    }

    debug!("Alias detection: entity='{}', samples={}", body.entity_name, body.text_samples.len());

    let linker = EntityLinker::new(state.pool.clone());

    let aliases = match linker.detect_aliases(
        &body.entity_id,
        &body.entity_name,
        &body.text_samples,
    ).await {
        Ok(aliases) => aliases,
        Err(e) => {
            error!("Alias detection failed: {}", e);
            return crate::handlers::response_builder::internal_error(
                &format!("Detection failed: {}", e)
            );
        }
    };

    let elapsed = start_time.elapsed().as_millis();
    let alias_count = aliases.len();
    info!("Alias detection completed: {} aliases found in {}ms", alias_count, elapsed);

    let response = DetectAliasesResponse {
        entity_id: body.entity_id.clone(),
        entity_name: body.entity_name.clone(),
        aliases,
        alias_count,
        process_time_ms: elapsed,
    };

    crate::handlers::response_builder::success_response(response)
}

/// POST /memory/synthesis/suggest-merges - Suggest entity merges
pub async fn suggest_merges_handler(
    req: HttpRequest,
    body: web::Json<SuggestMergesRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    // Validate JWT + rate limit
    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 50
    ) {
        return response;
    }

    // Validate threshold
    if body.similarity_threshold < 0.0 || body.similarity_threshold > 1.0 {
        return crate::handlers::response_builder::bad_request(
            "similarity_threshold must be 0.0-1.0"
        );
    }

    debug!("Merge suggestion: project='{}', threshold={}", body.project, body.similarity_threshold);

    let linker = EntityLinker::new(state.pool.clone());

    let suggestions = match linker.suggest_merges(&body.project, body.similarity_threshold).await {
        Ok(suggestions) => suggestions,
        Err(e) => {
            error!("Merge suggestion failed: {}", e);
            return crate::handlers::response_builder::internal_error(
                &format!("Suggestion failed: {}", e)
            );
        }
    };

    let elapsed = start_time.elapsed().as_millis();
    let suggestion_count = suggestions.len();
    info!("Merge suggestion completed: {} suggestions in {}ms", suggestion_count, elapsed);

    let response = SuggestMergesResponse {
        project: body.project.clone(),
        suggestions,
        suggestion_count,
        process_time_ms: elapsed,
    };

    crate::handlers::response_builder::success_response(response)
}

/// POST /memory/synthesis/detect-coreferences - Detect entity coreferences
pub async fn detect_coreferences_handler(
    req: HttpRequest,
    body: web::Json<DetectCoreferencesRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    // Validate JWT + rate limit
    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 100
    ) {
        return response;
    }

    // Validate input
    if body.texts.is_empty() {
        return crate::handlers::response_builder::bad_request(
            "texts cannot be empty"
        );
    }

    debug!("Coreference detection: project='{}', texts={}", body.project, body.texts.len());

    let linker = EntityLinker::new(state.pool.clone());

    let clusters = match linker.detect_coreferences(&body.texts, &body.project).await {
        Ok(clusters) => clusters,
        Err(e) => {
            error!("Coreference detection failed: {}", e);
            return crate::handlers::response_builder::internal_error(
                &format!("Detection failed: {}", e)
            );
        }
    };

    let total_mentions: usize = clusters.iter().map(|c| c.mention_count).sum();
    let elapsed = start_time.elapsed().as_millis();
    let cluster_count = clusters.len();

    info!("Coreference detection completed: {} clusters ({} mentions) in {}ms", 
          cluster_count, total_mentions, elapsed);

    let response = DetectCoreferencesResponse {
        project: body.project.clone(),
        clusters,
        cluster_count,
        total_mentions,
        process_time_ms: elapsed,
    };

    crate::handlers::response_builder::success_response(response)
}

/// Request for inference
#[derive(Debug, Deserialize)]
pub struct InferenceRequest {
    pub project: String,
    pub entity_id: String,
    pub rules: Vec<InferenceRule>,
    #[serde(default = "default_max_hops")]
    pub max_hops: usize,
}

/// Response from inference
#[derive(Debug, Serialize)]
pub struct InferenceResponse {
    pub entity_id: String,
    pub inferred_facts: Vec<InferredFact>,
    pub fact_count: usize,
    pub process_time_ms: u128,
}

/// Request for transitive closure
#[derive(Debug, Deserialize)]
pub struct TransitiveClosureRequest {
    pub project: String,
    pub entity_id: String,
    pub relation_type: Option<String>,
    #[serde(default = "default_max_hops")]
    pub max_hops: usize,
}

/// Response from transitive closure
#[derive(Debug, Serialize)]
pub struct TransitiveClosureResponse {
    pub source_entity: String,
    pub closure: TransitiveClosure,
    pub process_time_ms: u128,
}

/// Request for reasoning paths
#[derive(Debug, Deserialize)]
pub struct ReasoningPathsRequest {
    pub project: String,
    pub source_id: String,
    pub target_id: String,
    #[serde(default = "default_max_hops")]
    pub max_hops: usize,
}

/// Response from reasoning paths
#[derive(Debug, Serialize)]
pub struct ReasoningPathsResponse {
    pub source_id: String,
    pub target_id: String,
    pub paths: Vec<ReasoningPath>,
    pub path_count: usize,
    pub process_time_ms: u128,
}

fn default_max_hops() -> usize { 3 }

/// POST /memory/synthesis/infer - Apply inference rules
pub async fn infer_facts_handler(
    req: HttpRequest,
    body: web::Json<InferenceRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 50
    ) {
        return response;
    }

    if body.entity_id.is_empty() {
        return crate::handlers::response_builder::bad_request("entity_id required");
    }

    if body.max_hops == 0 || body.max_hops > 5 {
        return crate::handlers::response_builder::bad_request("max_hops must be 1-5");
    }

    debug!("Inference: entity='{}', hops={}", body.entity_id, body.max_hops);

    let engine = InferenceEngine::new(state.pool.clone(), body.rules.clone());
    let inferred = match engine.infer_facts(&body.project, &body.entity_id, body.max_hops).await {
        Ok(f) => f,
        Err(e) => {
            error!("Inference failed: {}", e);
            return crate::handlers::response_builder::internal_error(&format!("Failed: {}", e));
        }
    };

    let elapsed = start_time.elapsed().as_millis();
    info!("Inference: {} facts in {}ms", inferred.len(), elapsed);

    crate::handlers::response_builder::success_response(InferenceResponse {
        entity_id: body.entity_id.clone(),
        inferred_facts: inferred.clone(),
        fact_count: inferred.len(),
        process_time_ms: elapsed,
    })
}

/// POST /memory/synthesis/transitive-closure - Compute transitive closure
pub async fn transitive_closure_handler(
    req: HttpRequest,
    body: web::Json<TransitiveClosureRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 50
    ) {
        return response;
    }

    if body.entity_id.is_empty() {
        return crate::handlers::response_builder::bad_request("entity_id required");
    }

    if body.max_hops == 0 || body.max_hops > 5 {
        return crate::handlers::response_builder::bad_request("max_hops must be 1-5");
    }

    debug!("Transitive closure: entity='{}'", body.entity_id);

    let engine = InferenceEngine::new(state.pool.clone(), vec![]);
    let closure = match engine.transitive_closure(
        &body.entity_id, &body.project,
        body.relation_type.as_deref(), body.max_hops
    ).await {
        Ok(c) => c,
        Err(e) => {
            error!("Closure failed: {}", e);
            return crate::handlers::response_builder::internal_error(&format!("Failed: {}", e));
        }
    };

    let elapsed = start_time.elapsed().as_millis();
    info!("Closure: {} entities in {}ms", closure.entity_count, elapsed);

    crate::handlers::response_builder::success_response(TransitiveClosureResponse {
        source_entity: body.entity_id.clone(),
        closure,
        process_time_ms: elapsed,
    })
}

/// POST /memory/synthesis/reasoning-paths - Find reasoning paths
pub async fn reasoning_paths_handler(
    req: HttpRequest,
    body: web::Json<ReasoningPathsRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 100
    ) {
        return response;
    }

    if body.source_id.is_empty() || body.target_id.is_empty() {
        return crate::handlers::response_builder::bad_request("source_id and target_id required");
    }

    if body.max_hops == 0 || body.max_hops > 5 {
        return crate::handlers::response_builder::bad_request("max_hops must be 1-5");
    }

    debug!("Reasoning paths: {} → {}", body.source_id, body.target_id);

    let engine = InferenceEngine::new(state.pool.clone(), vec![]);
    let paths = match engine.find_reasoning_paths(
        &body.source_id, &body.target_id,
        &body.project, body.max_hops
    ).await {
        Ok(p) => p,
        Err(e) => {
            error!("Path finding failed: {}", e);
            return crate::handlers::response_builder::internal_error(&format!("Failed: {}", e));
        }
    };

    let elapsed = start_time.elapsed().as_millis();
    info!("Paths: {} found in {}ms", paths.len(), elapsed);

    crate::handlers::response_builder::success_response(ReasoningPathsResponse {
        source_id: body.source_id.clone(),
        target_id: body.target_id.clone(),
        paths,
        path_count: paths.len(),
        process_time_ms: elapsed,
    })
}

/// Request for query reasoning
#[derive(Debug, Deserialize)]
pub struct ReasonQueryRequest {
    pub project: String,
    pub question: String,
}

/// Response from query reasoning
#[derive(Debug, Serialize)]
pub struct ReasonQueryResponse {
    pub question: String,
    pub answers: Vec<String>,
    pub confidence: f32,
    pub reasoning_steps: Vec<ReasoningStepResponse>,
    pub explanation: String,
    pub process_time_ms: u128,
}

/// Reasoning step in response
#[derive(Debug, Serialize)]
pub struct ReasoningStepResponse {
    pub step_id: usize,
    pub question: String,
    pub results: Vec<String>,
    pub confidence: f32,
}

/// POST /memory/synthesis/reason - Answer complex questions via reasoning
pub async fn reason_query_handler(
    req: HttpRequest,
    body: web::Json<ReasonQueryRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 50
    ) {
        return response;
    }

    if body.question.is_empty() || body.question.len() > 1000 {
        return crate::handlers::response_builder::bad_request(
            "Question must be 1-1000 characters"
        );
    }

    debug!("Query reasoning: '{}'", body.question);

    let reasoner = QueryReasoner::new(state.pool.clone());

    // Decompose question
    let sub_queries = match reasoner.decompose_question(&body.question) {
        Ok(sq) => sq,
        Err(e) => {
            error!("Question decomposition failed: {}", e);
            return crate::handlers::response_builder::internal_error(
                &format!("Decomposition failed: {}", e)
            );
        }
    };

    // Execute reasoning
    let answer = match reasoner.reason_over_subqueries(sub_queries, &body.project).await {
        Ok(a) => a,
        Err(e) => {
            error!("Reasoning failed: {}", e);
            return crate::handlers::response_builder::internal_error(
                &format!("Reasoning failed: {}", e)
            );
        }
    };

    let elapsed = start_time.elapsed().as_millis();

    // Convert to response
    let steps: Vec<ReasoningStepResponse> = answer.reasoning_steps.iter().map(|step| {
        ReasoningStepResponse {
            step_id: step.step_id,
            question: step.sub_query.question.clone(),
            results: step.results.clone(),
            confidence: step.confidence,
        }
    }).collect();

    info!("Query reasoning completed: {} answers with {} steps in {}ms", 
          answer.answers.len(), answer.reasoning_steps.len(), elapsed);

    crate::handlers::response_builder::success_response(ReasonQueryResponse {
        question: answer.question,
        answers: answer.answers,
        confidence: answer.confidence,
        reasoning_steps: steps,
        explanation: answer.explanation,
        process_time_ms: elapsed,
    })
}

/// Request for content summarization
#[derive(Debug, Deserialize)]
pub struct SummarizeRequest {
    pub project: String,
    pub content: String,
    #[serde(default = "default_max_length")]
    pub max_length: usize,
    #[serde(default = "default_strategy")]
    pub strategy: String,
}

fn default_max_length() -> usize { 200 }
fn default_strategy() -> String { "hybrid".to_string() }

/// Response for summarization
#[derive(Debug, Serialize)]
pub struct SummarizeResponse {
    pub original_length: usize,
    pub summary: String,
    pub summary_length: usize,
    pub compression_ratio: f32,
    pub key_facts: Vec<KeyFactResponse>,
    pub coherence: f32,
    pub process_time_ms: u128,
}

/// Key fact in response
#[derive(Debug, Serialize)]
pub struct KeyFactResponse {
    pub fact: String,
    pub importance: f32,
    pub fact_type: String,
}

/// POST /memory/synthesis/summarize - Summarize and abstract results
pub async fn summarize_handler(
    req: HttpRequest,
    body: web::Json<SummarizeRequest>,
    state: web::Data<AppState>,
) -> HttpResponse {
    let start_time = std::time::Instant::now();

    if let Err(response) = crate::handlers::middleware::validate_and_rate_limit(
        &req, &state, "synthesis", 100
    ) {
        return response;
    }

    if body.content.is_empty() || body.content.len() > 50000 {
        return crate::handlers::response_builder::bad_request(
            "Content must be 1-50000 characters"
        );
    }

    if body.max_length < 50 || body.max_length > 10000 {
        return crate::handlers::response_builder::bad_request(
            "Max length must be 50-10000"
        );
    }

    debug!("Summarizing {} chars to ~{} chars", body.content.len(), body.max_length);

    let strategy = match body.strategy.to_lowercase().as_str() {
        "extractive" => SummarizationStrategy::Extractive,
        "abstractive" => SummarizationStrategy::Abstractive,
        "hybrid" | _ => SummarizationStrategy::Hybrid,
    };

    let summarizer = Summarizer::new();

    let summary = match summarizer.summarize(&body.content, body.max_length, strategy) {
        Ok(s) => s,
        Err(e) => {
            error!("Summarization failed: {}", e);
            return crate::handlers::response_builder::internal_error(
                &format!("Summarization failed: {}", e)
            );
        }
    };

    let elapsed = start_time.elapsed().as_millis();

    // Convert key facts to response
    let key_facts: Vec<KeyFactResponse> = summary.key_facts.into_iter().map(|kf| {
        KeyFactResponse {
            fact: kf.fact,
            importance: kf.importance,
            fact_type: kf.fact_type,
        }
    }).collect();

    info!("Summarization completed: {}% compression, {} key facts, coherence {:.2}%",
          (100.0 * summary.compression_ratio) as u32,
          key_facts.len(),
          summary.coherence * 100.0);

    crate::handlers::response_builder::success_response(SummarizeResponse {
        original_length: summary.original_length,
        summary: summary.text,
        summary_length: summary.summary_length,
        compression_ratio: summary.compression_ratio,
        key_facts,
        coherence: summary.coherence,
        process_time_ms: elapsed,
    })
}

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

    #[test]
    fn test_link_entities_request() {
        let req = LinkEntitiesRequest {
            project: "poimen".to_string(),
            text: "Kubernetes is a container orchestrator.".to_string(),
        };
        assert_eq!(req.project, "poimen");
        assert!(!req.text.is_empty());
    }

    #[test]
    fn test_detect_aliases_request() {
        let req = DetectAliasesRequest {
            project: "poimen".to_string(),
            entity_id: "e1".to_string(),
            entity_name: "Kubernetes".to_string(),
            text_samples: vec!["k8s is great".to_string()],
        };
        assert_eq!(req.entity_name, "Kubernetes");
        assert_eq!(req.text_samples.len(), 1);
    }

    #[test]
    fn test_suggest_merges_request() {
        let req = SuggestMergesRequest {
            project: "poimen".to_string(),
            similarity_threshold: 0.85,
        };
        assert_eq!(req.similarity_threshold, 0.85);
    }

    #[test]
    fn test_suggest_merges_default_threshold() {
        let req = SuggestMergesRequest {
            project: "poimen".to_string(),
            similarity_threshold: default_merge_threshold(),
        };
        assert_eq!(req.similarity_threshold, 0.8);
    }

    #[test]
    fn test_detect_coreferences_request() {
        let req = DetectCoreferencesRequest {
            project: "poimen".to_string(),
            texts: vec![
                "Kubernetes is great.".to_string(),
                "k8s makes deployments easy.".to_string(),
            ],
        };
        assert_eq!(req.texts.len(), 2);
    }

    #[test]
    fn test_link_entities_response() {
        let resp = LinkEntitiesResponse {
            links: vec![],
            unlinked: vec![],
            total_mentions: 0,
            link_rate: 0.0,
            process_time_ms: 100,
        };
        assert_eq!(resp.total_mentions, 0);
    }

    #[test]
    fn test_detect_aliases_response() {
        let resp = DetectAliasesResponse {
            entity_id: "e1".to_string(),
            entity_name: "Kubernetes".to_string(),
            aliases: vec![],
            alias_count: 0,
            process_time_ms: 100,
        };
        assert_eq!(resp.alias_count, 0);
    }

    #[test]
    fn test_suggest_merges_response() {
        let resp = SuggestMergesResponse {
            project: "poimen".to_string(),
            suggestions: vec![],
            suggestion_count: 0,
            process_time_ms: 100,
        };
        assert_eq!(resp.suggestion_count, 0);
    }

    #[test]
    fn test_detect_coreferences_response() {
        let resp = DetectCoreferencesResponse {
            project: "poimen".to_string(),
            clusters: vec![],
            cluster_count: 0,
            total_mentions: 0,
            process_time_ms: 100,
        };
        assert_eq!(resp.cluster_count, 0);
    }

    #[test]
    fn test_link_entities_request_serialization() {
        let req = LinkEntitiesRequest {
            project: "test".to_string(),
            text: "Kubernetes".to_string(),
        };
        let json = serde_json::to_string(&req).unwrap();
        assert!(json.contains("test"));
    }

    #[test]
    fn test_link_entities_response_serialization() {
        let resp = LinkEntitiesResponse {
            links: vec![],
            unlinked: vec![],
            total_mentions: 5,
            link_rate: 0.8,
            process_time_ms: 150,
        };
        let json = serde_json::to_string(&resp).unwrap();
        assert!(json.contains("0.8"));
    }
}