// Episodic digest generation: daily, weekly, monthly, auto
//
// Three digest levels form a temporal hierarchy: daily digests summarize
// journal entries, weekly digests summarize dailies, monthly digests
// summarize weeklies. All three share the same generate/auto-detect
// pipeline, parameterized by DigestLevel.

use crate::llm::{call_sonnet, semantic_keys};
use crate::store::{self, Store, new_relation};
use crate::neuro;
use crate::util::memory_subdir;

use chrono::{Datelike, Duration, Local, NaiveDate};
use regex::Regex;
use std::collections::{BTreeMap, BTreeSet};
use std::fs;
use std::path::{Path, PathBuf};

// --- Digest level descriptors ---

struct DigestLevel {
    name: &'static str,       // lowercase, used for filenames and display
    title: &'static str,      // capitalized, used in prompts
    period: &'static str,     // "Date", "Week", "Month"
    input_title: &'static str,
    timeout: u64,
    journal_input: bool,      // true for daily (journal entries), false for child digests
    gather: fn(&Store, &str) -> Result<(String, Vec<(String, String)>), String>,
    find_args: fn(&[String], &str) -> Vec<String>,
}

const DAILY: DigestLevel = DigestLevel {
    name: "daily",
    title: "Daily",
    period: "Date",
    input_title: "Journal entries",
    timeout: 300,
    journal_input: true,
    gather: gather_daily,
    find_args: find_daily_args,
};

const WEEKLY: DigestLevel = DigestLevel {
    name: "weekly",
    title: "Weekly",
    period: "Week",
    input_title: "Daily digests",
    timeout: 300,
    journal_input: false,
    gather: gather_weekly,
    find_args: find_weekly_args,
};

const MONTHLY: DigestLevel = DigestLevel {
    name: "monthly",
    title: "Monthly",
    period: "Month",
    input_title: "Weekly digests",
    timeout: 600,
    journal_input: false,
    gather: gather_monthly,
    find_args: find_monthly_args,
};

// --- Input gathering ---

/// Load child digest files from the episodic directory.
fn load_child_digests(prefix: &str, labels: &[String]) -> Result<Vec<(String, String)>, String> {
    let dir = memory_subdir("episodic")?;
    let mut digests = Vec::new();
    for label in labels {
        let path = dir.join(format!("{}-{}.md", prefix, label));
        if let Ok(content) = fs::read_to_string(&path) {
            digests.push((label.clone(), content));
        }
    }
    Ok(digests)
}

fn find_daily_args(dates: &[String], today: &str) -> Vec<String> {
    dates.iter()
        .filter(|d| d.as_str() != today)
        .cloned()
        .collect()
}

fn find_weekly_args(dates: &[String], today: &str) -> Vec<String> {
    let mut weeks: BTreeMap<String, String> = BTreeMap::new();
    for date in dates {
        if let Ok((wl, _)) = week_dates(date) {
            weeks.entry(wl).or_insert_with(|| date.clone());
        }
    }
    weeks.into_values()
        .filter(|date| {
            week_dates(date).map_or(false, |(_, days)|
                days.last().unwrap() < &today.to_string())
        })
        .collect()
}

fn find_monthly_args(dates: &[String], _today: &str) -> Vec<String> {
    let now = Local::now();
    let cur = (now.year(), now.month());
    let mut months: BTreeSet<(i32, u32)> = BTreeSet::new();
    for date in dates {
        if let Ok(nd) = NaiveDate::parse_from_str(date, "%Y-%m-%d") {
            months.insert((nd.year(), nd.month()));
        }
    }
    months.into_iter()
        .filter(|ym| *ym < cur)
        .map(|(y, m)| format!("{}-{:02}", y, m))
        .collect()
}

fn gather_daily(store: &Store, date: &str) -> Result<(String, Vec<(String, String)>), String> {
    let date_re = Regex::new(&format!(
        r"^journal\.md#j-{}", regex::escape(date)
    )).unwrap();
    let mut entries: Vec<_> = store.nodes.values()
        .filter(|n| date_re.is_match(&n.key))
        .map(|n| {
            let label = n.key.strip_prefix("journal.md#j-").unwrap_or(&n.key);
            (label.to_string(), n.content.clone())
        })
        .collect();
    entries.sort_by(|a, b| a.0.cmp(&b.0));
    Ok((date.to_string(), entries))
}

fn gather_weekly(_store: &Store, date: &str) -> Result<(String, Vec<(String, String)>), String> {
    let (week_label, dates) = week_dates(date)?;
    let inputs = load_child_digests("daily", &dates)?;
    Ok((week_label, inputs))
}

fn gather_monthly(_store: &Store, arg: &str) -> Result<(String, Vec<(String, String)>), String> {
    let (year, month) = if arg.is_empty() {
        let now = Local::now();
        (now.year(), now.month())
    } else {
        let d = NaiveDate::parse_from_str(&format!("{}-01", arg), "%Y-%m-%d")
            .map_err(|e| format!("bad month '{}': {} (expected YYYY-MM)", arg, e))?;
        (d.year(), d.month())
    };
    let label = format!("{}-{:02}", year, month);
    let child_labels = weeks_in_month(year, month);
    let inputs = load_child_digests("weekly", &child_labels)?;
    Ok((label, inputs))
}

// --- Unified generator ---

fn format_inputs(inputs: &[(String, String)], daily: bool) -> String {
    let mut text = String::new();
    for (label, content) in inputs {
        if daily {
            text.push_str(&format!("\n### {}\n\n{}\n", label, content));
        } else {
            text.push_str(&format!("\n---\n## {}\n{}\n", label, content));
        }
    }
    text
}

fn generate_digest(
    store: &mut Store,
    level: &DigestLevel,
    label: &str,
    inputs: &[(String, String)],
) -> Result<(), String> {
    println!("Generating {} digest for {}...", level.name, label);

    if inputs.is_empty() {
        println!("  No inputs found for {}", label);
        return Ok(());
    }
    println!("  {} inputs", inputs.len());

    let keys = semantic_keys(store);
    let keys_text = keys.iter()
        .map(|k| format!("  - {}", k))
        .collect::<Vec<_>>()
        .join("\n");

    let content = format_inputs(inputs, level.journal_input);
    let covered = inputs.iter()
        .map(|(l, _)| l.as_str())
        .collect::<Vec<_>>()
        .join(", ");

    let prompt = neuro::load_prompt("digest", &[
        ("{{LEVEL}}", level.title),
        ("{{PERIOD}}", level.period),
        ("{{INPUT_TITLE}}", level.input_title),
        ("{{LABEL}}", label),
        ("{{CONTENT}}", &content),
        ("{{COVERED}}", &covered),
        ("{{KEYS}}", &keys_text),
    ])?;
    println!("  Prompt: {} chars (~{} tokens)", prompt.len(), prompt.len() / 4);

    println!("  Calling Sonnet...");
    let digest = call_sonnet(&prompt, level.timeout)?;

    let output_path = memory_subdir("episodic")?
        .join(format!("{}-{}.md", level.name, label));
    fs::write(&output_path, &digest)
        .map_err(|e| format!("write {}: {}", output_path.display(), e))?;
    println!("  Written: {}", output_path.display());

    store.import_file(&output_path)?;
    store.save()?;

    println!("  Done: {} lines", digest.lines().count());
    Ok(())
}

// --- Public API ---

pub fn generate_daily(store: &mut Store, date: &str) -> Result<(), String> {
    let (label, inputs) = (DAILY.gather)(store, date)?;
    generate_digest(store, &DAILY, &label, &inputs)
}

pub fn generate_weekly(store: &mut Store, date: &str) -> Result<(), String> {
    let (label, inputs) = (WEEKLY.gather)(store, date)?;
    generate_digest(store, &WEEKLY, &label, &inputs)
}

pub fn generate_monthly(store: &mut Store, month_arg: &str) -> Result<(), String> {
    let (label, inputs) = (MONTHLY.gather)(store, month_arg)?;
    generate_digest(store, &MONTHLY, &label, &inputs)
}

// --- Date helpers ---

/// Get ISO week label and the 7 dates (Mon-Sun) for the week containing `date`.
fn week_dates(date: &str) -> Result<(String, Vec<String>), String> {
    let nd = NaiveDate::parse_from_str(date, "%Y-%m-%d")
        .map_err(|e| format!("bad date '{}': {}", date, e))?;
    let iso = nd.iso_week();
    let week_label = format!("{}-W{:02}", iso.year(), iso.week());
    let monday = nd - Duration::days(nd.weekday().num_days_from_monday() as i64);
    let dates = (0..7)
        .map(|i| (monday + Duration::days(i)).format("%Y-%m-%d").to_string())
        .collect();
    Ok((week_label, dates))
}

fn weeks_in_month(year: i32, month: u32) -> Vec<String> {
    let mut weeks = BTreeSet::new();
    let mut d = 1u32;
    while let Some(date) = NaiveDate::from_ymd_opt(year, month, d) {
        if date.month() != month { break; }
        let iso = date.iso_week();
        weeks.insert(format!("{}-W{:02}", iso.year(), iso.week()));
        d += 1;
    }
    weeks.into_iter().collect()
}

// --- Auto-detect and generate missing digests ---

const LEVELS: &[&DigestLevel] = &[&DAILY, &WEEKLY, &MONTHLY];

pub fn digest_auto(store: &mut Store) -> Result<(), String> {
    let today = Local::now().format("%Y-%m-%d").to_string();
    let epi = memory_subdir("episodic")?;

    // Collect all dates with journal entries
    let date_re = Regex::new(r"^\d{4}-\d{2}-\d{2}").unwrap();
    let dates: Vec<String> = store.nodes.keys()
        .filter_map(|key| {
            key.strip_prefix("journal.md#j-")
                .filter(|rest| rest.len() >= 10 && date_re.is_match(rest))
                .map(|rest| rest[..10].to_string())
        })
        .collect::<BTreeSet<_>>()
        .into_iter()
        .collect();

    let mut total = 0u32;

    for level in LEVELS {
        let args = (level.find_args)(&dates, &today);
        let mut generated = 0u32;
        let mut skipped = 0u32;

        for arg in &args {
            let (label, inputs) = (level.gather)(store, arg)?;
            if epi.join(format!("{}-{}.md", level.name, label)).exists() {
                skipped += 1;
                continue;
            }
            if inputs.is_empty() { continue; }
            println!("[auto] Missing {} digest for {}", level.name, label);
            generate_digest(store, level, &label, &inputs)?;
            generated += 1;
        }

        println!("[auto] {}: {} generated, {} existed", level.name, generated, skipped);
        total += generated;
    }

    if total == 0 {
        println!("[auto] All digests up to date.");
    } else {
        println!("[auto] Generated {} total digests.", total);
    }
    Ok(())
}


// --- Digest link parsing ---
// Replaces digest-link-parser.py: parses ## Links sections from digest
// files and applies them to the memory graph.

/// A parsed link from a digest's Links section.
pub struct DigestLink {
    pub source: String,
    pub target: String,
    pub reason: String,
    pub file: String,
}

/// Normalize a raw link target to a poc-memory key.
fn normalize_link_key(raw: &str) -> String {
    let key = raw.trim().trim_matches('`').trim();
    if key.is_empty() { return String::new(); }

    // Self-references
    let lower = key.to_lowercase();
    if lower.starts_with("this ") { return String::new(); }

    let mut key = key.to_string();

    // weekly/2026-W06 → weekly-2026-W06, etc.
    if let Some(pos) = key.find('/') {
        let prefix = &key[..pos];
        if prefix == "daily" || prefix == "weekly" || prefix == "monthly" {
            let rest = &key[pos + 1..];
            key = format!("{}-{}", prefix, rest);
        }
    }

    // daily-2026-02-04 → daily-2026-02-04.md
    let re = Regex::new(r"^(daily|weekly|monthly)-\d{4}").unwrap();
    if re.is_match(&key) && !key.ends_with(".md") {
        key.push_str(".md");
    }

    // Bare date → daily digest
    let date_re = Regex::new(r"^\d{4}-\d{2}-\d{2}$").unwrap();
    if date_re.is_match(key.strip_suffix(".md").unwrap_or(&key)) {
        let date = key.strip_suffix(".md").unwrap_or(&key);
        key = format!("daily-{}.md", date);
    }

    // Ensure .md extension
    if key.contains('#') {
        let (file, section) = key.split_once('#').unwrap();
        if !file.ends_with(".md") {
            key = format!("{}.md#{}", file, section);
        }
    } else if !key.ends_with(".md") && !key.contains('/') && !key.starts_with("NEW:") {
        key.push_str(".md");
    }

    key
}

/// Parse the Links section from a single digest file.
fn parse_digest_file_links(path: &Path) -> Vec<DigestLink> {
    let content = match fs::read_to_string(path) {
        Ok(c) => c,
        Err(_) => return Vec::new(),
    };

    let digest_name = path.file_stem()
        .and_then(|s| s.to_str())
        .unwrap_or("");
    let digest_key = format!("{}.md", digest_name);
    let filename = path.file_name()
        .and_then(|s| s.to_str())
        .unwrap_or("")
        .to_string();

    let link_re = Regex::new(r"^-\s+(.+?)\s*[→↔←]\s*(.+?)(?:\s*\((.+?)\))?\s*$").unwrap();
    let header_re = Regex::new(r"^##\s+Links").unwrap();
    let mut links = Vec::new();
    let mut in_links = false;

    for line in content.lines() {
        if header_re.is_match(line) {
            in_links = true;
            continue;
        }
        if in_links && line.starts_with("## ") {
            in_links = false;
            continue;
        }
        if !in_links { continue; }
        if line.starts_with("###") || line.starts_with("**") { continue; }

        if let Some(cap) = link_re.captures(line) {
            let raw_source = cap[1].trim();
            let raw_target = cap[2].trim();
            let reason = cap.get(3).map(|m| m.as_str().to_string()).unwrap_or_default();

            let mut source = normalize_link_key(raw_source);
            let mut target = normalize_link_key(raw_target);

            // Replace self-references with digest key
            if source.is_empty() { source = digest_key.clone(); }
            if target.is_empty() { target = digest_key.clone(); }

            // Handle "this daily/weekly/monthly" in raw text
            let raw_s_lower = raw_source.to_lowercase();
            let raw_t_lower = raw_target.to_lowercase();
            if raw_s_lower.contains("this daily") || raw_s_lower.contains("this weekly")
                || raw_s_lower.contains("this monthly")
            {
                source = digest_key.clone();
            }
            if raw_t_lower.contains("this daily") || raw_t_lower.contains("this weekly")
                || raw_t_lower.contains("this monthly")
            {
                target = digest_key.clone();
            }

            // Skip NEW: and self-links
            if source.starts_with("NEW:") || target.starts_with("NEW:") { continue; }
            if source == target { continue; }

            links.push(DigestLink { source, target, reason, file: filename.clone() });
        }
    }

    links
}

/// Parse links from all digest files in the episodic dir.
pub fn parse_all_digest_links() -> Result<Vec<DigestLink>, String> {
    let dir = memory_subdir("episodic")?;
    let mut all_links = Vec::new();

    for pattern in &["daily-*.md", "weekly-*.md", "monthly-*.md"] {
        if let Ok(entries) = fs::read_dir(&dir) {
            let mut files: Vec<PathBuf> = entries
                .filter_map(|e| e.ok())
                .map(|e| e.path())
                .filter(|p| {
                    p.file_name()
                        .and_then(|n| n.to_str())
                        .map(|n| {
                            let prefix = pattern.split('*').next().unwrap_or("");
                            n.starts_with(prefix) && n.ends_with(".md")
                        })
                        .unwrap_or(false)
                })
                .collect();
            files.sort();
            for path in files {
                all_links.extend(parse_digest_file_links(&path));
            }
        }
    }

    // Deduplicate by (source, target) pair
    let mut seen = std::collections::HashSet::new();
    all_links.retain(|link| seen.insert((link.source.clone(), link.target.clone())));

    Ok(all_links)
}

/// Apply parsed digest links to the store.
pub fn apply_digest_links(store: &mut Store, links: &[DigestLink]) -> (usize, usize, usize) {
    let mut applied = 0usize;
    let mut skipped = 0usize;
    let mut fallbacks = 0usize;

    for link in links {
        // Try resolving both keys
        let source = match store.resolve_key(&link.source) {
            Ok(s) => s,
            Err(_) => {
                // Try stripping section anchor as fallback
                if let Some(base) = link.source.split('#').next() {
                    match store.resolve_key(base) {
                        Ok(s) => { fallbacks += 1; s }
                        Err(_) => { skipped += 1; continue; }
                    }
                } else {
                    skipped += 1; continue;
                }
            }
        };
        let target = match store.resolve_key(&link.target) {
            Ok(t) => t,
            Err(_) => {
                if let Some(base) = link.target.split('#').next() {
                    match store.resolve_key(base) {
                        Ok(t) => { fallbacks += 1; t }
                        Err(_) => { skipped += 1; continue; }
                    }
                } else {
                    skipped += 1; continue;
                }
            }
        };

        // Refine target to best-matching section if available
        let source_content = store.nodes.get(&source)
            .map(|n| n.content.as_str()).unwrap_or("");
        let target = neuro::refine_target(store, source_content, &target);

        if source == target { skipped += 1; continue; }

        // Check if link already exists
        let exists = store.relations.iter().any(|r|
            r.source_key == source && r.target_key == target && !r.deleted
        );
        if exists { skipped += 1; continue; }

        let source_uuid = match store.nodes.get(&source) {
            Some(n) => n.uuid,
            None => { skipped += 1; continue; }
        };
        let target_uuid = match store.nodes.get(&target) {
            Some(n) => n.uuid,
            None => { skipped += 1; continue; }
        };

        let rel = new_relation(
            source_uuid, target_uuid,
            store::RelationType::Link,
            0.5,
            &source, &target,
        );
        if store.add_relation(rel).is_ok() {
            println!("  + {} → {}", source, target);
            applied += 1;
        }
    }

    (applied, skipped, fallbacks)
}