// training.rs — Memory importance scoring via /v1/score
//
// Drops each memory from the context one at a time, calls the vLLM
// /v1/score endpoint to get logprobs for assistant responses.
// Produces a divergence matrix: memories × responses.
//
// Row sums = memory importance (for graph weight updates)
// Column sums = response memory-dependence (training candidates)

use std::time::Instant;

use super::api::ApiClient;
use crate::agent::api::types::*;
use crate::agent::context::{ConversationEntry, ContextState};
use crate::user::ui_channel::{UiMessage, UiSender};

/// Timeout for individual /v1/score API calls.
const SCORE_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(120);

/// Result of scoring one conversation's memory usage.
pub struct MemoryScore {
    /// memory_key → importance score (sum of divergence across all responses)
    pub memory_weights: Vec<(String, f64)>,
    /// response_index → memory-dependence score (sum of divergence across all memories)
    pub response_scores: Vec<f64>,
    /// Full matrix: divergence[memory_idx][response_idx]
    pub matrix: Vec<Vec<f64>>,
    /// Keys of memories that were scored
    pub memory_keys: Vec<String>,
    /// Conversation entry indices of the assistant responses
    pub response_entry_indices: Vec<usize>,
}

impl MemoryScore {
    /// Get the most important memories for a given conversation entry index.
    pub fn important_memories_for_entry(&self, entry_idx: usize) -> Vec<(&str, f64)> {
        let Some(resp_idx) = self.response_entry_indices.iter().position(|&i| i == entry_idx)
        else { return Vec::new() };

        let mut result: Vec<(&str, f64)> = self.memory_keys.iter()
            .zip(self.matrix.iter())
            .filter_map(|(key, row)| {
                let score = row.get(resp_idx).copied().unwrap_or(0.0);
                if score > 0.01 { Some((key.as_str(), score)) } else { None }
            })
            .collect();
        result.sort_by(|a, b| b.1.partial_cmp(&a.1).unwrap_or(std::cmp::Ordering::Equal));
        result
    }
}

/// Score how important each memory is to the conversation.
pub async fn score_memories(
    context: &ContextState,
    client: &ApiClient,
    ui_tx: &UiSender,
) -> anyhow::Result<MemoryScore> {
    let _ = ui_tx.send(UiMessage::Debug(format!(
        "[training] in score_memories"
    )));

    let memories: Vec<(usize, String)> = context.entries.iter().enumerate()
        .filter_map(|(i, e)| match e {
            ConversationEntry::Memory { key, .. } => Some((i, key.clone())),
            _ => None,
        })
        .collect();

    let response_indices: Vec<usize> = context.entries.iter().enumerate()
        .filter(|(_, e)| e.message().role == Role::Assistant)
        .map(|(i, _)| i)
        .collect();

    if memories.is_empty() || response_indices.is_empty() {
        let _ = ui_tx.send(UiMessage::Debug(
            "[training] nothing to score (no memories or no responses)".into()
        ));
        return Ok(MemoryScore {
            memory_weights: Vec::new(),
            response_scores: Vec::new(),
            matrix: Vec::new(),
            memory_keys: Vec::new(),
            response_entry_indices: Vec::new(),
        });
    }

    let _ = ui_tx.send(UiMessage::Info(format!(
        "[scoring {} memories × {} responses]",
        memories.len(), response_indices.len(),
    )));

    let http = reqwest::Client::builder()
        .timeout(SCORE_TIMEOUT)
        .pool_max_idle_per_host(2)
        .build()
        .unwrap_or_default();

    let all_messages = build_messages(context);

    let _ = ui_tx.send(UiMessage::Debug(format!(
        "[training] {} messages in context",
        all_messages.len(),
    )));

    // Baseline: score with all memories present
    let _ = ui_tx.send(UiMessage::Debug("[training] serializing payload...".into()));
    let payload_size = serde_json::to_string(&all_messages)
        .map(|s| s.len()).unwrap_or(0);
    let _ = ui_tx.send(UiMessage::Debug(format!(
        "[training] payload size: {}KB",
        payload_size / 1024,
    )));
    let _ = ui_tx.send(UiMessage::Activity("scoring baseline...".into()));
    let start = Instant::now();
    let baseline = call_score(&http, client, &all_messages).await?;
    let _ = ui_tx.send(UiMessage::Debug(format!(
        "[training] baseline: {} responses scored in {:.1}s",
        baseline.len(), start.elapsed().as_secs_f64(),
    )));

    // For each memory, drop it and measure divergence
    let mut matrix: Vec<Vec<f64>> = Vec::new();
    let memory_keys: Vec<String> = memories.iter().map(|(_, k)| k.clone()).collect();
    let total = memories.len();

    for (mem_idx, (entry_idx, key)) in memories.iter().enumerate() {
        let _ = ui_tx.send(UiMessage::Activity(format!(
            "scoring {}/{}: {}...", mem_idx + 1, total, key,
        )));

        let start = Instant::now();
        let filtered_messages = build_messages_without(context, *entry_idx);
        let without = call_score(&http, client, &filtered_messages).await;

        match without {
            Ok(without) => {
                let elapsed = start.elapsed().as_secs_f64();
                // Match scores by position (nth scored response),
                // not message_index — indices shift when a memory
                // is removed from the conversation.
                let mut row = Vec::new();
                for (i, base_score) in baseline.iter().enumerate() {
                    let base_lp = base_score.total_logprob;
                    let without_lp = without.get(i)
                        .map(|s| s.total_logprob)
                        .unwrap_or(base_lp);
                    let divergence = (base_lp - without_lp).max(0.0);
                    row.push(divergence);
                }
                let importance: f64 = row.iter().sum();
                let _ = ui_tx.send(UiMessage::Debug(format!(
                    "[training] {}/{} {} → {:.1} ({:.1}s)",
                    mem_idx + 1, total, key, importance, elapsed,
                )));
                matrix.push(row);
            }
            Err(e) => {
                let _ = ui_tx.send(UiMessage::Debug(format!(
                    "[training] {}/{} {} FAILED: {:#}",
                    mem_idx + 1, total, key, e,
                )));
                // Push zero row so matrix stays aligned
                matrix.push(vec![0.0; baseline.len()]);
            }
        }
    }

    let _ = ui_tx.send(UiMessage::Activity(String::new()));

    // Compute scores
    let memory_weights: Vec<(String, f64)> = memory_keys.iter()
        .zip(matrix.iter())
        .map(|(key, row)| (key.clone(), row.iter().sum()))
        .collect();

    let n_responses = response_indices.len();
    let mut response_scores = vec![0.0; n_responses];
    for row in &matrix {
        for (j, &v) in row.iter().enumerate() {
            if j < n_responses {
                response_scores[j] += v;
            }
        }
    }

    let _ = ui_tx.send(UiMessage::Info(format!(
        "[scoring complete: {} memories scored]",
        memory_keys.len(),
    )));

    Ok(MemoryScore {
        memory_weights,
        response_scores,
        matrix,
        memory_keys,
        response_entry_indices: response_indices,
    })
}

/// Score response from the /v1/score endpoint.
#[derive(serde::Deserialize)]
struct ScoreMessageResult {
    #[allow(dead_code)]
    message_index: usize,
    total_logprob: f64,
}

#[derive(serde::Deserialize)]
struct ScoreApiResponse {
    scores: Vec<ScoreMessageResult>,
}

/// Build the messages array for the /v1/score endpoint from ContextState.
fn build_messages(context: &ContextState) -> Vec<serde_json::Value> {
    let mut msgs = Vec::new();
    msgs.push(serde_json::json!({"role": "system", "content": &context.system_prompt}));
    let ctx = context.render_context_message();
    if !ctx.is_empty() {
        msgs.push(serde_json::json!({"role": "user", "content": ctx}));
    }
    for entry in &context.entries {
        let m = entry.api_message();
        msgs.push(serde_json::json!({
            "role": m.role_str(),
            "content": m.content_text(),
        }));
    }
    msgs
}

/// Build messages with one entry removed.
fn build_messages_without(context: &ContextState, skip_idx: usize) -> Vec<serde_json::Value> {
    let mut msgs = Vec::new();
    msgs.push(serde_json::json!({"role": "system", "content": &context.system_prompt}));
    let ctx = context.render_context_message();
    if !ctx.is_empty() {
        msgs.push(serde_json::json!({"role": "user", "content": ctx}));
    }
    for (i, entry) in context.entries.iter().enumerate() {
        if i == skip_idx { continue; }
        let m = entry.api_message();
        msgs.push(serde_json::json!({
            "role": m.role_str(),
            "content": m.content_text(),
        }));
    }
    msgs
}

/// Call the /v1/score endpoint and return per-message logprobs.
async fn call_score(
    http: &reqwest::Client,
    client: &ApiClient,
    messages: &[serde_json::Value],
) -> anyhow::Result<Vec<ScoreMessageResult>> {
    let request = serde_json::json!({
        "model": client.model,
        "messages": messages,
        "logprobs": 1,
    });

    let response = http
        .post(format!("{}/score", client.base_url()))
        .header("Content-Type", "application/json")
        .header("Authorization", format!("Bearer {}", client.api_key()))
        .json(&request)
        .send()
        .await
        .map_err(|e| {
            if e.is_timeout() {
                anyhow::anyhow!("score request timed out after {}s", SCORE_TIMEOUT.as_secs())
            } else {
                anyhow::anyhow!("score request failed: {}", e)
            }
        })?;

    let status = response.status();
    let body: serde_json::Value = response.json().await?;

    if !status.is_success() {
        let msg = body.get("error")
            .and_then(|e| e.as_str())
            .unwrap_or("unknown error");
        anyhow::bail!("score API HTTP {}: {}", status, msg);
    }

    // Check for error in body (score endpoint returns dict on error)
    if let Some(err) = body.get("error").and_then(|e| e.as_str()) {
        anyhow::bail!("score API error: {}", err);
    }

    let result: ScoreApiResponse = serde_json::from_value(body)
        .map_err(|e| anyhow::anyhow!("failed to parse score response: {}", e))?;
    Ok(result.scores)
}