// training.rs — Memory importance scoring via /v1/score
//
// Three scoring modes, all built on the same call_score() primitive:
//
// score_memories()  — Full N×M matrix (memories × responses) for the
//                     debug screen. Expensive: N+1 API calls.
//
// memory_score()    — Single memory importance. Scores the 50 messages
//                     after it was surfaced, with/without that memory.
//                     2 API calls.
//
// finetune_score()  — Identifies training candidates. Scores recent
//                     messages with all memories stripped. Responses
//                     with high divergence depend on memories the model
//                     hasn't internalized. 2 API calls.

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

const SCORE_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(120);

// ── Message building ────────────────────────────────────────────

/// What to filter when building the message array for scoring.
enum Filter<'a> {
    None,
    SkipIndex(usize),
    SkipKey(&'a str),
    SkipAllMemories,
}

/// Build the messages array for a scoring call.
///
/// Always includes system prompt + context message as prefix, then
/// entries from `range` filtered by `filter`.
fn build_messages(
    context: &ContextState,
    range: std::ops::Range<usize>,
    filter: Filter,
) -> Vec<serde_json::Value> {
    let mut msgs = vec![
        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 in range {
        let entry = &context.entries[i];
        let skip = match &filter {
            Filter::None => false,
            Filter::SkipIndex(idx) => i == *idx,
            Filter::SkipKey(key) => matches!(entry, ConversationEntry::Memory { key: k, .. } if k == key),
            Filter::SkipAllMemories => entry.is_memory(),
        };
        if skip { continue; }
        let m = entry.api_message();
        msgs.push(serde_json::json!({
            "role": m.role_str(),
            "content": m.content_text(),
        }));
    }
    msgs
}

// ── Score API ───────────────────────────────────────────────────

#[derive(serde::Deserialize)]
struct ScoreResult {
    total_logprob: f64,
}

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

fn http_client() -> reqwest::Client {
    reqwest::Client::builder()
        .timeout(SCORE_TIMEOUT)
        .pool_max_idle_per_host(2)
        .build()
        .unwrap_or_default()
}

async fn call_score(
    http: &reqwest::Client,
    client: &ApiClient,
    messages: &[serde_json::Value],
) -> anyhow::Result<Vec<ScoreResult>> {
    let response = http
        .post(format!("{}/score", client.base_url()))
        .header("Content-Type", "application/json")
        .header("Authorization", format!("Bearer {}", client.api_key()))
        .json(&serde_json::json!({
            "model": client.model,
            "messages": messages,
            "logprobs": 1,
        }))
        .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);
    }
    if let Some(err) = body.get("error").and_then(|e| e.as_str()) {
        anyhow::bail!("score API error: {}", err);
    }

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

/// Compute per-position logprob divergence: how much worse the model
/// scores each response without something vs with it.
fn divergence(baseline: &[ScoreResult], without: &[ScoreResult]) -> Vec<f64> {
    baseline.iter().enumerate()
        .map(|(i, base)| {
            let without_lp = without.get(i).map(|s| s.total_logprob).unwrap_or(base.total_logprob);
            (base.total_logprob - without_lp).max(0.0)
        })
        .collect()
}

/// Score two message sets and return total divergence.
async fn score_divergence(
    http: &reqwest::Client,
    client: &ApiClient,
    context: &ContextState,
    range: std::ops::Range<usize>,
    filter: Filter<'_>,
) -> anyhow::Result<(Vec<f64>, Vec<ScoreResult>)> {
    let baseline = call_score(http, client, &build_messages(context, range.clone(), Filter::None)).await?;
    let without = call_score(http, client, &build_messages(context, range, filter)).await?;
    let divs = divergence(&baseline, &without);
    Ok((divs, baseline))
}

// ── Full matrix scoring (debug screen) ──────────────────────────

/// Result of scoring one conversation's memory usage.
pub struct MemoryScore {
    pub memory_weights: Vec<(String, f64)>,
    pub response_scores: Vec<f64>,
    /// Full matrix: divergence[memory_idx][response_idx]
    pub matrix: Vec<Vec<f64>>,
    pub memory_keys: Vec<String>,
    pub response_entry_indices: Vec<usize>,
}

impl MemoryScore {
    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 (full matrix).
pub async fn score_memories(
    context: &ContextState,
    client: &ApiClient,
    ui_tx: &UiSender,
) -> anyhow::Result<MemoryScore> {
    let mut memory_keys: Vec<String> = context.entries.iter()
        .filter_map(|e| match e {
            ConversationEntry::Memory { key, .. } => Some(key.clone()),
            _ => None,
        })
        .collect();
    memory_keys.dedup();

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

    if memory_keys.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::Info(format!(
        "[scoring {} memories × {} responses]", memory_keys.len(), response_indices.len(),
    )));

    let http = http_client();
    let range = 0..context.entries.len();

    let _ = ui_tx.send(UiMessage::Activity("scoring baseline...".into()));
    let baseline = call_score(&http, client, &build_messages(context, range.clone(), Filter::None)).await?;

    let total = memory_keys.len();
    let mut matrix: Vec<Vec<f64>> = Vec::new();

    for (mem_idx, key) in memory_keys.iter().enumerate() {
        let _ = ui_tx.send(UiMessage::Activity(format!(
            "scoring {}/{}: {}...", mem_idx + 1, total, key,
        )));
        let msgs = build_messages(context, range.clone(), Filter::SkipKey(key));
        match call_score(&http, client, &msgs).await {
            Ok(without) => matrix.push(divergence(&baseline, &without)),
            Err(e) => {
                let _ = ui_tx.send(UiMessage::Debug(format!(
                    "[training] {} FAILED: {:#}", key, e,
                )));
                matrix.push(vec![0.0; baseline.len()]);
            }
        }
    }

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

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

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

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

// ── Single memory scoring ───────────────────────────────────────

/// Score how important a single memory is to the conversation.
///
/// Scores the 50 messages after the memory was surfaced — the window
/// where it could have influenced responses. Returns the sum of
/// divergence, or 0.0 if the memory isn't in the conversation.
pub async fn score_memory(
    context: &ContextState,
    key: &str,
    client: &ApiClient,
    ui_tx: &UiSender,
) -> anyhow::Result<f64> {
    const WINDOW: usize = 50;

    let first_pos = match context.entries.iter().position(|e| {
        matches!(e, ConversationEntry::Memory { key: k, .. } if k == key)
    }) {
        Some(p) => p,
        None => return Ok(0.0),
    };

    let range = first_pos..(first_pos + WINDOW).min(context.entries.len());
    if !context.entries[range.clone()].iter().any(|e| e.message().role == Role::Assistant) {
        return Ok(0.0);
    }

    let http = http_client();
    let _ = ui_tx.send(UiMessage::Activity(format!("scoring memory: {}...", key)));
    let (divs, _) = score_divergence(&http, client, context, range, Filter::SkipKey(key)).await?;
    let _ = ui_tx.send(UiMessage::Activity(String::new()));

    Ok(divs.iter().sum())
}

// ── Background memory scoring ───────────────────────────────────

/// Incrementally score memories through the conversation.
///
/// Walks memory entries in conversation order starting from `cursor`.
/// For each memory with a full WINDOW after it, calls score_memory()
/// and yields the result. Stops at the first memory that doesn't have
/// enough messages yet — the conversation needs to grow before we can
/// score it.
///
/// Returns the updated cursor (entry index to resume from next time)
/// and the scores for each memory that was scored this round.
pub async fn score_memories_incremental(
    context: &ContextState,
    cursor: usize,
    client: &ApiClient,
    ui_tx: &UiSender,
) -> anyhow::Result<(usize, Vec<(String, f64)>)> {
    const WINDOW: usize = 50;

    // Collect unique memory keys with their first position, starting from cursor
    let mut seen = std::collections::HashSet::new();
    let mut to_score: Vec<(usize, String)> = Vec::new();

    for (i, entry) in context.entries.iter().enumerate().skip(cursor) {
        if let ConversationEntry::Memory { key, .. } = entry {
            if seen.insert(key.clone()) {
                to_score.push((i, key.clone()));
            }
        }
    }

    let http = http_client();
    let mut new_cursor = cursor;
    let mut results = Vec::new();

    for (pos, key) in &to_score {
        let end = pos + WINDOW;

        // Not enough conversation after this memory yet — stop here
        if end > context.entries.len() {
            break;
        }

        // Need at least one assistant response in the window
        let range = *pos..end;
        if !context.entries[range.clone()].iter().any(|e| e.message().role == Role::Assistant) {
            new_cursor = end;
            continue;
        }

        let _ = ui_tx.send(UiMessage::Activity(format!("scoring memory: {}...", key)));
        match score_divergence(&http, client, context, range, Filter::SkipKey(key)).await {
            Ok((divs, _)) => {
                let importance: f64 = divs.iter().sum();
                let _ = ui_tx.send(UiMessage::Debug(format!(
                    "[scoring] {} → {:.2}", key, importance,
                )));
                results.push((key.clone(), importance));
            }
            Err(e) => {
                let _ = ui_tx.send(UiMessage::Debug(format!(
                    "[scoring] {} FAILED: {:#}", key, e,
                )));
            }
        }
        new_cursor = end;
    }

    let _ = ui_tx.send(UiMessage::Activity(String::new()));
    Ok((new_cursor, results))
}

// ── Fine-tuning scoring ─────────────────────────────────────────

/// Score which recent responses are candidates for fine-tuning.
///
/// Removes all memories and scores the most recent `count` messages.
/// Responses with high divergence depend on memories the model hasn't
/// internalized — these are fine-tuning candidates.
///
/// Returns (entry_index, divergence) pairs, sorted by divergence descending.
pub async fn score_finetune(
    context: &ContextState,
    count: usize,
    client: &ApiClient,
    ui_tx: &UiSender,
) -> anyhow::Result<Vec<(usize, f64)>> {
    let range = context.entries.len().saturating_sub(count)..context.entries.len();

    let response_positions: Vec<usize> = range.clone()
        .filter(|&i| context.entries[i].message().role == Role::Assistant)
        .collect();
    if response_positions.is_empty() {
        return Ok(Vec::new());
    }

    let http = http_client();
    let _ = ui_tx.send(UiMessage::Activity("scoring for fine-tuning...".into()));
    let (divs, _) = score_divergence(&http, client, context, range, Filter::SkipAllMemories).await?;
    let _ = ui_tx.send(UiMessage::Activity(String::new()));

    let mut results: Vec<(usize, f64)> = response_positions.iter()
        .enumerate()
        .map(|(i, &entry_idx)| (entry_idx, divs.get(i).copied().unwrap_or(0.0)))
        .collect();
    results.sort_by(|a, b| b.1.partial_cmp(&a.1).unwrap_or(std::cmp::Ordering::Equal));
    Ok(results)
}