//! M3.7.4 — `/memory/context` endpoint
//!
//! Three-tier context lookup for failure diagnosis:
//! 1. Exact signature match (failure_signature table)
//! 2. Vector search on symptoms + text
//! 3. Reference corpus fallback
//!
//! Returns: {"tier": 1|2|3, "lessons": [...], "skills": [...], "budget": {...}}

use anyhow::Result;
use serde::{Deserialize, Serialize};
use std::sync::Arc;

/// Request to the context endpoint
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ContextRequest {
    /// Tool name (e.g., "github-actions", "docker", "kubectl")
    pub tool: Option<String>,
    
    /// Task or operation name
    pub task: Option<String>,
    
    /// Raw error/log output for signature extraction
    pub signature_source: Option<String>,
    
    /// Project ID (defaults to "all" for federation)
    pub project: Option<String>,
    
    /// Scope: "project" or "all-projects"
    pub scope: Option<String>,
    
    /// Token budget for response (default: 6000)
    pub budget: Option<usize>,
}

/// A retrieved lesson with tier information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TieredLesson {
    pub tier: u8,  // 1, 2, or 3
    pub level: String,  // L0, L1, L2, R
    pub score: Option<f32>,  // Similarity score (tier 2+)
    pub seen_count: Option<i32>,  // How many times we've seen this (tier 1)
    pub last_seen: Option<String>,  // When we last saw this (tier 1)
    pub matched_kind: Option<String>,  // "symptom" or "text" for tier 2
    pub text: String,  // Content
    pub parents: Option<Vec<serde_json::Value>>,  // Provenance chain
}

/// A skill recommendation
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SkillRecommendation {
    pub name: String,
    pub score: f32,
    pub description: Option<String>,
}

/// Budget tracking
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BudgetInfo {
    pub limit: usize,
    pub used: usize,
    pub dropped: Vec<String>,  // What was dropped to stay in budget
}

/// Response from the context endpoint
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ContextResponse {
    pub tier: u8,  // Highest tier that has results (1, 2, or 3)
    pub lessons: Vec<TieredLesson>,
    pub skills: Vec<SkillRecommendation>,
    pub budget: BudgetInfo,
    pub degraded: Option<bool>,  // If some leg failed (skills timeout, etc.)
}

impl Default for ContextResponse {
    fn default() -> Self {
        Self {
            tier: 0,
            lessons: vec![],
            skills: vec![],
            budget: BudgetInfo {
                limit: 6000,
                used: 0,
                dropped: vec![],
            },
            degraded: None,
        }
    }
}

/// Context lookup orchestrator
pub struct ContextLookup {
    pub budget_limit: usize,
    pub project: String,
    pub scope: String,
}

impl ContextLookup {
    pub fn new(budget_limit: usize, project: String, scope: String) -> Self {
        Self {
            budget_limit,
            project,
            scope,
        }
    }

    /// Execute three-tier context lookup
    pub async fn lookup(&self, req: ContextRequest) -> Result<ContextResponse> {
        let mut response = ContextResponse {
            budget: BudgetInfo {
                limit: req.budget.unwrap_or(6000),
                used: 0,
                dropped: vec![],
            },
            ..Default::default()
        };

        // Validate that at least one input is provided
        if req.tool.is_none() && req.task.is_none() && req.signature_source.is_none() {
            anyhow::bail!("At least one of tool, task, or signature_source is required");
        }

        // Tier 1: Exact signature match
        if let Some(sig_source) = &req.signature_source {
            // Extract signature from raw log (M3.7.7)
            // TODO: Call signature extractor
            tracing::debug!("Tier 1: Looking up signature");
        }

        // Tier 2: Vector search (concurrent)
        if response.lessons.is_empty() {
            tracing::debug!("Tier 2: Vector search on symptoms");
            // TODO: Search pgvector for similar symptoms
            // TODO: Search for related text
            // TODO: Merge and rerank
        }

        // Tier 3: Reference corpus fallback
        if response.budget.used < response.budget.limit {
            tracing::debug!("Tier 3: Fallback to reference corpus");
            // TODO: Query Obsidian reference docs
        }

        // Concurrent: Skills recommendations
        // TODO: Call skills endpoint with timeout
        response.skills = vec![];

        // Set response tier (highest tier with results)
        response.tier = if !response.lessons.is_empty() {
            response
                .lessons
                .iter()
                .map(|l| l.tier)
                .max()
                .unwrap_or(0)
        } else {
            0
        };

        tracing::info!(
            tier = response.tier,
            lesson_count = response.lessons.len(),
            skill_count = response.skills.len(),
            budget_used = response.budget.used,
            "context lookup complete"
        );

        Ok(response)
    }
}

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

    #[test]
    fn test_context_response_default() {
        let resp = ContextResponse::default();
        assert_eq!(resp.tier, 0);
        assert_eq!(resp.lessons.len(), 0);
        assert_eq!(resp.budget.limit, 6000);
    }

    #[test]
    fn test_context_request_validation() {
        let req = ContextRequest {
            tool: None,
            task: None,
            signature_source: None,
            project: None,
            scope: None,
            budget: None,
        };

        // Should require at least one input
        assert!(req.tool.is_none());
    }

    #[test]
    fn test_tiered_lesson_creation() {
        let lesson = TieredLesson {
            tier: 1,
            level: "L1".to_string(),
            score: None,
            seen_count: Some(3),
            last_seen: Some("2024-01-15".to_string()),
            matched_kind: None,
            text: "npm ci --legacy-peer-deps".to_string(),
            parents: None,
        };

        assert_eq!(lesson.tier, 1);
        assert_eq!(lesson.seen_count, Some(3));
    }

    #[test]
    fn test_budget_info_default() {
        let budget = BudgetInfo {
            limit: 6000,
            used: 2140,
            dropped: vec!["reference".to_string()],
        };

        assert_eq!(budget.limit - budget.used, 3860);
    }

    #[tokio::test]
    async fn test_context_lookup_empty_request() {
        let lookup = ContextLookup::new(6000, "test".to_string(), "project".to_string());
        let req = ContextRequest {
            tool: None,
            task: None,
            signature_source: None,
            project: None,
            scope: None,
            budget: None,
        };

        let result = lookup.lookup(req).await;
        assert!(result.is_err());
    }

    #[tokio::test]
    async fn test_context_lookup_with_tool() {
        let lookup = ContextLookup::new(6000, "test".to_string(), "project".to_string());
        let req = ContextRequest {
            tool: Some("github-actions".to_string()),
            task: None,
            signature_source: None,
            project: Some("test".to_string()),
            scope: None,
            budget: Some(6000),
        };

        let result = lookup.lookup(req).await;
        assert!(result.is_ok());
        let resp = result.unwrap();
        assert_eq!(resp.budget.limit, 6000);
    }

    #[test]
    fn test_skill_recommendation() {
        let skill = SkillRecommendation {
            name: "ci-triage".to_string(),
            score: 0.77,
            description: Some("CI troubleshooting".to_string()),
        };

        assert_eq!(skill.name, "ci-triage");
        assert!(skill.score > 0.7);
    }
}