// training.rs — Memory importance scoring via prompt logprobs
//
// Drops each memory from the context one at a time, runs prompt_logprobs
// to see how the model's confidence in its responses changes. Produces
// a divergence matrix: memories × responses.
//
// Row sums = memory importance (for graph weight updates)
// Column sums = response memory-dependence (training candidates)

use crate::agent::api::ApiClient;
use crate::agent::types::*;
use crate::agent::ui_channel::UiSender;

/// 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 (maps response_idx → entry_idx)
    pub response_entry_indices: Vec<usize>,
}

impl MemoryScore {
    /// Get the most important memories for a given conversation entry index.
    /// Returns (memory_key, divergence_score) sorted by importance.
    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.
///
/// For each Memory entry in the context, builds a version without it
/// and checks how the model's logprobs change for assistant responses.
pub async fn score_memories(
    context: &ContextState,
    client: &ApiClient,
    ui_tx: &UiSender,
) -> anyhow::Result<MemoryScore> {
    use crate::agent::ui_channel::UiMessage;

    // Identify memory entries and assistant response positions
    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() {
        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::Debug(format!(
        "[training] scoring {} memories × {} responses",
        memories.len(), response_indices.len(),
    )));

    // Shared HTTP client for connection reuse across all scoring calls
    let http = reqwest::Client::builder()
        .pool_max_idle_per_host(2)
        .build()
        .unwrap_or_default();

    // Baseline: logprobs with all memories present
    let baseline = get_response_logprobs(context, &context.entries, client, &http, ui_tx).await?;

    let _ = ui_tx.send(UiMessage::Debug(format!(
        "[training] baseline: {} response tokens scored",
        baseline.iter().map(|r| r.len()).sum::<usize>(),
    )));

    // 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();

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

        // Build entries without this memory
        let filtered: Vec<ConversationEntry> = context.entries.iter().enumerate()
            .filter(|(i, _)| *i != *entry_idx)
            .map(|(_, e)| e.clone())
            .collect();

        let without = get_response_logprobs(context, &filtered, client, &http, ui_tx).await?;

        // Compute per-response divergence
        let mut row = Vec::new();
        for (_resp_idx, (base_lps, without_lps)) in baseline.iter().zip(without.iter()).enumerate() {
            // Sum of logprob drops across tokens in this response
            // Positive = memory helped (logprob was higher with it)
            let divergence: f64 = base_lps.iter().zip(without_lps.iter())
                .map(|(b, w)| b - w) // positive when baseline was more confident
                .filter(|d| *d > 0.0) // only count where memory helped
                .sum();
            row.push(divergence);
        }
        matrix.push(row);
    }

    // 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::Activity(String::new()));

    // Log summary per memory
    for (key, score) in &memory_weights {
        let _ = ui_tx.send(UiMessage::Debug(format!(
            "[training] {} → importance {:.1}", key, score,
        )));
    }

    // Log per-response breakdown for the most important memories
    let mut sorted_mems: Vec<(usize, &str, f64)> = memory_keys.iter().enumerate()
        .map(|(i, k)| (i, k.as_str(), memory_weights[i].1))
        .collect();
    sorted_mems.sort_by(|a, b| b.2.partial_cmp(&a.2).unwrap_or(std::cmp::Ordering::Equal));

    for (mem_i, key, total) in sorted_mems.iter().take(5) {
        if *total <= 0.0 { continue; }
        let row = &matrix[*mem_i];
        let top_responses: Vec<String> = row.iter().enumerate()
            .filter(|(_, v)| **v > 0.1)
            .map(|(j, v)| format!("resp[{}]={:.1}", j, v))
            .collect();
        if !top_responses.is_empty() {
            let _ = ui_tx.send(UiMessage::Debug(format!(
                "[training]   {} ({:.1}): {}", key, total, top_responses.join(", "),
            )));
        }
    }

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

/// Rough token estimate: ~4 chars per token.
const CHARS_PER_TOKEN: usize = 4;

/// Get logprobs for all assistant response tokens in a conversation.
/// Returns a Vec<Vec<f64>> — one inner vec per assistant response,
/// containing logprobs for each token in that response.
///
/// Chunks the conversation into ~50K token segments (rounded to
/// assistant message boundaries) to avoid OOM from the logprobs
/// tensor allocation.
async fn get_response_logprobs(
    context: &ContextState,
    entries: &[ConversationEntry],
    client: &ApiClient,
    http: &reqwest::Client,
    ui_tx: &UiSender,
) -> anyhow::Result<Vec<Vec<f64>>> {
    // Build the fixed prefix (system prompt + personality)
    let mut prefix = Vec::new();
    prefix.push(Message::system(&context.system_prompt));
    let ctx = context.render_context_message();
    if !ctx.is_empty() {
        prefix.push(Message::user(ctx));
    }
    let prefix_chars: usize = prefix.iter()
        .map(|m| m.content_text().len())
        .sum();

    // Split entries into chunks that fit within the token budget,
    // each ending at an assistant message boundary.
    let max_chunk_chars = crate::config::get().scoring_chunk_tokens * CHARS_PER_TOKEN;
    let budget = max_chunk_chars.saturating_sub(prefix_chars);
    let chunks = chunk_entries(entries, budget);

    let mut all_responses: Vec<Vec<f64>> = Vec::new();

    use crate::agent::ui_channel::UiMessage;
    let _ = ui_tx.send(UiMessage::Debug(format!(
        "[training] {} chunks, prefix={}K chars, budget={}K chars",
        chunks.len(), prefix_chars / 1024, budget / 1024,
    )));

    for (chunk_idx, chunk) in chunks.iter().enumerate() {
        let chunk_chars: usize = chunk.iter()
            .map(|e| e.message().content_text().len())
            .sum();
        let _ = ui_tx.send(UiMessage::Debug(format!(
            "[training] chunk {}/{}: {} entries, {}K chars",
            chunk_idx + 1, chunks.len(), chunk.len(), chunk_chars / 1024,
        )));
    }

    for chunk in &chunks {
        let mut msgs = prefix.clone();
        msgs.extend(chunk.iter().map(|e| e.api_message().clone()));

        let result = call_prompt_logprobs(&msgs, client, http).await?;
        all_responses.extend(result);
    }

    Ok(all_responses)
}

/// Split entries into chunks of approximately `budget_chars` each,
/// ending at assistant message boundaries.
fn chunk_entries(entries: &[ConversationEntry], budget_chars: usize) -> Vec<Vec<ConversationEntry>> {
    let mut chunks = Vec::new();
    let mut current = Vec::new();
    let mut current_chars = 0;

    for entry in entries {
        let entry_chars = entry.message().content_text().len();
        current_chars += entry_chars;
        current.push(entry.clone());

        // If over budget and we just added an assistant message, cut here
        if current_chars >= budget_chars && entry.message().role == Role::Assistant {
            chunks.push(std::mem::take(&mut current));
            current_chars = 0;
        }
    }

    if !current.is_empty() {
        chunks.push(current);
    }

    // If everything fit in one chunk, just return it
    if chunks.is_empty() {
        chunks.push(entries.to_vec());
    }

    chunks
}

/// Make a single prompt_logprobs API call and extract response logprobs.
async fn call_prompt_logprobs(
    msgs: &[Message],
    client: &ApiClient,
    http: &reqwest::Client,
) -> anyhow::Result<Vec<Vec<f64>>> {
    let request = serde_json::json!({
        "model": client.model,
        "messages": msgs,
        "max_tokens": 1,
        "prompt_logprobs": 1,
        "stream": false,
    });

    let response = http
        .post(format!("{}/chat/completions", client.base_url()))
        .header("Content-Type", "application/json")
        .header("Authorization", format!("Bearer {}", client.api_key()))
        .json(&request)
        .send()
        .await?;

    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.get("message"))
            .and_then(|m| m.as_str())
            .unwrap_or("unknown error");
        anyhow::bail!("HTTP {} from logprobs API: {}", status, msg);
    }

    let prompt_logprobs = body.get("prompt_logprobs")
        .and_then(|v| v.as_array())
        .ok_or_else(|| anyhow::anyhow!("no prompt_logprobs in response"))?;

    // Find assistant response boundaries using special tokens
    // Pattern: <|im_start|> assistant \n [<think>...</think>] response <|im_end|>
    let mut responses: Vec<Vec<f64>> = Vec::new();
    let mut in_assistant = false;
    let mut in_think = false;
    let mut current_response: Vec<f64> = Vec::new();

    for entry in prompt_logprobs {
        let Some(obj) = entry.as_object() else { continue };
        let first = obj.values().next();
        let Some(info) = first.and_then(|v| v.as_object()) else { continue };
        let token = info.get("decoded_token").and_then(|v| v.as_str()).unwrap_or("");
        let logprob = info.get("logprob").and_then(|v| v.as_f64()).unwrap_or(0.0);

        match token {
            "<|im_start|>" => {
                in_assistant = false;
                in_think = false;
            }
            "assistant" if !in_assistant => {
                in_assistant = true;
                in_think = false;
                current_response.clear();
            }
            "<think>" if in_assistant => {
                in_think = true;
            }
            "</think>" if in_assistant => {
                in_think = false;
            }
            "<|im_end|>" if in_assistant => {
                if !current_response.is_empty() {
                    responses.push(std::mem::take(&mut current_response));
                }
                in_assistant = false;
            }
            "\n" if in_assistant && current_response.is_empty() => {
                // Skip the newline right after "assistant"
            }
            _ if in_assistant && !in_think => {
                current_response.push(logprob);
            }
            _ => {}
        }
    }

    Ok(responses)
}