use std::fs;
use std::path::{Path, PathBuf};
use std::sync::{Arc, RwLock};
use std::time::Instant;

use anyhow::{Context, Result};
use chrono::{DateTime, Utc};
use chrono_tz::Tz;
use serde::Serialize;
use tracing::warn;

use crate::rtr::cache::{CacheAvailability, CacheMemoryStats, SharedRtrCache, VersionReportStats};
use crate::rtr::config::{RuntimeConfig, format_timezone};
use crate::rtr::server::{RtrNotifier, RtrServiceStats, RtrTransportConnectionCounts};
use crate::source::pipeline::{
    DataQualityReport, FileFingerprint, SourceFingerprint, SourceLoadReport,
};

#[derive(Clone, Serialize)]
pub struct ReportConfiguration {
    source_refresh_interval_seconds: u64,
    runtime_report_interval_seconds: u64,
    report_history_limit: usize,
    max_delta: u8,
    prune_delta_by_snapshot_size: bool,
    strict_ccr_validation: bool,
    timezone: String,
    timing: TimingReport,
}

#[derive(Clone, Copy, Serialize)]
struct TimingReport {
    refresh: u32,
    retry: u32,
    expire: u32,
}

impl ReportConfiguration {
    pub fn new(
        source_refresh_interval_seconds: u64,
        runtime_report_interval_seconds: u64,
        report_history_limit: usize,
        max_delta: u8,
        prune_delta_by_snapshot_size: bool,
        strict_ccr_validation: bool,
        timezone: Tz,
        timing: (u32, u32, u32),
    ) -> Self {
        Self {
            source_refresh_interval_seconds,
            runtime_report_interval_seconds,
            report_history_limit,
            max_delta,
            prune_delta_by_snapshot_size,
            strict_ccr_validation,
            timezone: format_timezone(timezone),
            timing: TimingReport {
                refresh: timing.0,
                retry: timing.1,
                expire: timing.2,
            },
        }
    }

    pub fn timezone(&self) -> Tz {
        self.timezone
            .parse::<Tz>()
            .expect("serialized timezone should be a valid IANA timezone")
    }
}

#[derive(Clone)]
pub struct ReportContext {
    started_at: DateTime<Utc>,
    started_instant: Instant,
    configuration: Arc<RwLock<ReportConfiguration>>,
    runtime: Arc<RwLock<RuntimeReportState>>,
}

#[derive(Debug, Clone, Default)]
struct RuntimeReportState {
    source: Option<SourceLoadReport>,
    source_fingerprint: Option<SourceFingerprint>,
    data_quality: Option<DataQualityReport>,
    refresh: RefreshReport,
}

#[derive(Debug, Clone, Serialize)]
struct RefreshReport {
    last_attempt_at: Option<DateTime<Utc>>,
    last_success_at: Option<DateTime<Utc>>,
    last_changed_at: Option<DateTime<Utc>>,
    status: &'static str,
    changed: Option<bool>,
    duration_ms: Option<u128>,
    consecutive_failures: u64,
    last_error: Option<String>,
}

#[derive(Serialize)]
struct RefreshReportView {
    last_attempt_at: Option<DateTime<Tz>>,
    last_success_at: Option<DateTime<Tz>>,
    last_changed_at: Option<DateTime<Tz>>,
    status: &'static str,
    changed: Option<bool>,
    duration_ms: Option<u128>,
    consecutive_failures: u64,
    last_error: Option<String>,
}

impl RefreshReportView {
    fn from_report(report: RefreshReport, timezone: Tz) -> Self {
        Self {
            last_attempt_at: report
                .last_attempt_at
                .map(|time| to_report_time(time, timezone)),
            last_success_at: report
                .last_success_at
                .map(|time| to_report_time(time, timezone)),
            last_changed_at: report
                .last_changed_at
                .map(|time| to_report_time(time, timezone)),
            status: report.status,
            changed: report.changed,
            duration_ms: report.duration_ms,
            consecutive_failures: report.consecutive_failures,
            last_error: report.last_error,
        }
    }
}

impl Default for RefreshReport {
    fn default() -> Self {
        Self {
            last_attempt_at: None,
            last_success_at: None,
            last_changed_at: None,
            status: "not_attempted",
            changed: None,
            duration_ms: None,
            consecutive_failures: 0,
            last_error: None,
        }
    }
}

impl ReportContext {
    pub fn new(configuration: ReportConfiguration) -> Self {
        Self {
            started_at: Utc::now(),
            started_instant: Instant::now(),
            configuration: Arc::new(RwLock::new(configuration)),
            runtime: Arc::new(RwLock::new(RuntimeReportState::default())),
        }
    }

    pub fn update_runtime_config(&self, config: &RuntimeConfig) {
        let timezone = config
            .timezone()
            .expect("runtime config timezone should be validated before report update");
        let mut configuration = self
            .configuration
            .write()
            .unwrap_or_else(|poisoned| poisoned.into_inner());
        *configuration = ReportConfiguration::new(
            config.source_refresh_interval_seconds,
            config.runtime_report_interval_seconds,
            config.report_history_limit,
            config.max_delta,
            config.prune_delta_by_snapshot_size,
            config.strict_ccr_validation,
            timezone,
            (
                config.timing.refresh,
                config.timing.retry,
                config.timing.expire,
            ),
        );
    }

    pub fn record_refresh_success(
        &self,
        attempted_at: DateTime<Utc>,
        duration_ms: u128,
        changed: bool,
        source: SourceLoadReport,
        data_quality: DataQualityReport,
    ) {
        let mut state = self
            .runtime
            .write()
            .unwrap_or_else(|poisoned| poisoned.into_inner());
        state.source = Some(source);
        state.data_quality = Some(data_quality);
        state.refresh.last_attempt_at = Some(attempted_at);
        state.refresh.last_success_at = Some(Utc::now());
        if changed {
            state.refresh.last_changed_at = Some(Utc::now());
        }
        state.refresh.status = "success";
        state.refresh.changed = Some(changed);
        state.refresh.duration_ms = Some(duration_ms);
        state.refresh.consecutive_failures = 0;
        state.refresh.last_error = None;
    }

    pub fn record_source_fingerprint(&self, fingerprint: SourceFingerprint) {
        let mut state = self
            .runtime
            .write()
            .unwrap_or_else(|poisoned| poisoned.into_inner());
        state.source_fingerprint = Some(fingerprint);
    }

    pub fn record_refresh_unchanged(&self, attempted_at: DateTime<Utc>, duration_ms: u128) {
        let mut state = self
            .runtime
            .write()
            .unwrap_or_else(|poisoned| poisoned.into_inner());
        state.refresh.last_attempt_at = Some(attempted_at);
        state.refresh.last_success_at = Some(Utc::now());
        state.refresh.status = "success";
        state.refresh.changed = Some(false);
        state.refresh.duration_ms = Some(duration_ms);
        state.refresh.consecutive_failures = 0;
        state.refresh.last_error = None;
    }

    pub fn record_refresh_failure(
        &self,
        attempted_at: DateTime<Utc>,
        duration_ms: u128,
        error: &anyhow::Error,
    ) {
        let mut state = self
            .runtime
            .write()
            .unwrap_or_else(|poisoned| poisoned.into_inner());
        state.refresh.last_attempt_at = Some(attempted_at);
        state.refresh.status = "failed";
        state.refresh.changed = None;
        state.refresh.duration_ms = Some(duration_ms);
        state.refresh.consecutive_failures = state.refresh.consecutive_failures.saturating_add(1);
        state.refresh.last_error = Some(error.to_string());
    }

    pub fn write_or_warn(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) {
        if let Err(err) = self.write(report_dir, phase, shared_cache, notifier, service_stats) {
            warn!(
                "failed to write RTR report to {}: {:?}",
                report_dir.display(),
                err
            );
        }
    }

    pub fn write_source_or_warn(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) {
        if let Err(err) =
            self.write_source(report_dir, phase, shared_cache, notifier, service_stats)
        {
            warn!(
                "failed to write RTR source report to {}: {:?}",
                report_dir.display(),
                err
            );
        }
    }

    pub fn write_clients_or_warn(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) {
        if let Err(err) =
            self.write_clients(report_dir, phase, shared_cache, notifier, service_stats)
        {
            warn!(
                "failed to write RTR clients report to {}: {:?}",
                report_dir.display(),
                err
            );
        }
    }

    pub fn write_runtime_or_warn(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) {
        if let Err(err) =
            self.write_runtime(report_dir, phase, shared_cache, notifier, service_stats)
        {
            warn!(
                "failed to write RTR runtime report to {}: {:?}",
                report_dir.display(),
                err
            );
        }
    }

    fn write(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) -> Result<()> {
        let parts = self.build_reports(phase, shared_cache, notifier, service_stats);
        fs::create_dir_all(report_dir)
            .with_context(|| format!("create report directory {}", report_dir.display()))?;
        self.write_source_report(report_dir, &parts.suffix, &parts.source)?;
        self.write_clients_report(report_dir, &parts.suffix, &parts.clients)?;
        self.write_runtime_report(report_dir, &parts.suffix, &parts.runtime)?;
        Ok(())
    }

    fn write_source(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) -> Result<()> {
        let parts = self.build_reports(phase, shared_cache, notifier, service_stats);
        fs::create_dir_all(report_dir)
            .with_context(|| format!("create report directory {}", report_dir.display()))?;
        self.write_source_report(report_dir, &parts.suffix, &parts.source)
    }

    fn write_clients(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) -> Result<()> {
        let parts = self.build_reports(phase, shared_cache, notifier, service_stats);
        fs::create_dir_all(report_dir)
            .with_context(|| format!("create report directory {}", report_dir.display()))?;
        self.write_clients_report(report_dir, &parts.suffix, &parts.clients)
    }

    fn write_runtime(
        &self,
        report_dir: &Path,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) -> Result<()> {
        let parts = self.build_reports(phase, shared_cache, notifier, service_stats);
        fs::create_dir_all(report_dir)
            .with_context(|| format!("create report directory {}", report_dir.display()))?;
        self.write_runtime_report(report_dir, &parts.suffix, &parts.runtime)
    }

    fn build_reports(
        &self,
        phase: &str,
        shared_cache: &SharedRtrCache,
        notifier: &RtrNotifier,
        service_stats: &RtrServiceStats,
    ) -> ReportParts {
        let cache = shared_cache.load_full();
        let configuration = self
            .configuration
            .read()
            .unwrap_or_else(|poisoned| poisoned.into_inner())
            .clone();
        let timezone = configuration.timezone();
        let runtime = self
            .runtime
            .read()
            .unwrap_or_else(|poisoned| poisoned.into_inner())
            .clone();
        let availability = match cache.availability() {
            CacheAvailability::Ready => "ready",
            CacheAvailability::NoDataAvailable => "no_data_available",
        };
        let active_connections = service_stats.active_connections();
        let connections_by_transport = service_stats.transport_connections();
        let max_connections = service_stats.max_connections();
        let generated_at = self.report_now(timezone);
        let metadata = ReportMetadata {
            schema_version: 2,
            generated_at,
            phase: phase.to_string(),
        };
        let service = ServiceReport {
            started_at: self.to_report_time(self.started_at, timezone),
            uptime_seconds: self.started_instant.elapsed().as_secs(),
            active_connections,
            connections_by_transport: TransportConnectionReport::from(connections_by_transport),
            session_listeners: notifier.listener_count(),
            max_connections,
            connection_utilization: active_connections as f64 / max_connections as f64,
        };
        let process = ProcessReport {
            rss_mib: current_rss_mib(),
        };
        let source = runtime
            .source
            .map(|source| SourceLoadReportView::from_report(source, timezone));
        let refresh = RefreshReportView::from_report(runtime.refresh, timezone);
        let cache = CacheReport {
            availability,
            created_at: self.to_report_time(cache.created_at().utc(), timezone),
            last_update_begin: self.to_report_time(cache.last_update_begin().utc(), timezone),
            last_update_end: self.to_report_time(cache.last_update_end().utc(), timezone),
            memory: cache.memory_stats(),
            versions: cache.version_report_stats(),
        };

        let source_report = SourceReport {
            schema_version: metadata.schema_version,
            generated_at: metadata.generated_at,
            phase: metadata.phase.clone(),
            source,
            source_fingerprint: runtime.source_fingerprint.map(|fingerprint| {
                SourceFingerprintReport::from_fingerprint(fingerprint, timezone)
            }),
            refresh,
            data_quality: runtime.data_quality,
            cache,
        };
        let clients_report = ClientsReport {
            schema_version: metadata.schema_version,
            generated_at: metadata.generated_at,
            phase: metadata.phase.clone(),
            service: ServiceReport {
                started_at: service.started_at,
                uptime_seconds: service.uptime_seconds,
                active_connections: service.active_connections,
                connections_by_transport: service.connections_by_transport,
                session_listeners: service.session_listeners,
                max_connections: service.max_connections,
                connection_utilization: service.connection_utilization,
            },
        };
        let runtime_report = RuntimeReport {
            schema_version: metadata.schema_version,
            generated_at: metadata.generated_at,
            phase: metadata.phase,
            service,
            process,
            configuration,
        };
        let suffix = report_file_suffix(generated_at);

        ReportParts {
            suffix,
            source: source_report,
            clients: clients_report,
            runtime: runtime_report,
        }
    }

    fn write_source_report(
        &self,
        report_dir: &Path,
        suffix: &str,
        report: &SourceReport,
    ) -> Result<()> {
        write_rolling_report(
            report_dir,
            "rtr-source",
            suffix,
            self.report_history_limit(),
            report,
        )
    }

    fn write_clients_report(
        &self,
        report_dir: &Path,
        suffix: &str,
        report: &ClientsReport,
    ) -> Result<()> {
        write_rolling_report(
            report_dir,
            "rtr-clients",
            suffix,
            self.report_history_limit(),
            report,
        )
    }

    fn write_runtime_report(
        &self,
        report_dir: &Path,
        suffix: &str,
        report: &RuntimeReport,
    ) -> Result<()> {
        write_rolling_report(
            report_dir,
            "rtr-runtime",
            suffix,
            self.report_history_limit(),
            report,
        )
    }

    fn report_history_limit(&self) -> usize {
        self.configuration
            .read()
            .unwrap_or_else(|poisoned| poisoned.into_inner())
            .report_history_limit
    }

    fn report_now(&self, timezone: Tz) -> DateTime<Tz> {
        self.to_report_time(Utc::now(), timezone)
    }

    fn to_report_time(&self, time: DateTime<Utc>, timezone: Tz) -> DateTime<Tz> {
        time.with_timezone(&timezone)
    }
}

#[derive(Serialize, Clone)]
struct ReportMetadata {
    schema_version: u16,
    generated_at: DateTime<Tz>,
    phase: String,
}

struct ReportParts {
    suffix: String,
    source: SourceReport,
    clients: ClientsReport,
    runtime: RuntimeReport,
}

#[derive(Serialize)]
struct SourceReport {
    schema_version: u16,
    generated_at: DateTime<Tz>,
    phase: String,
    source: Option<SourceLoadReportView>,
    source_fingerprint: Option<SourceFingerprintReport>,
    refresh: RefreshReportView,
    data_quality: Option<DataQualityReport>,
    cache: CacheReport,
}

#[derive(Serialize)]
struct ClientsReport {
    schema_version: u16,
    generated_at: DateTime<Tz>,
    phase: String,
    service: ServiceReport,
}

#[derive(Serialize)]
struct RuntimeReport {
    schema_version: u16,
    generated_at: DateTime<Tz>,
    phase: String,
    service: ServiceReport,
    process: ProcessReport,
    configuration: ReportConfiguration,
}

#[derive(Clone, Copy, Serialize)]
struct ServiceReport {
    started_at: DateTime<Tz>,
    uptime_seconds: u64,
    active_connections: usize,
    connections_by_transport: TransportConnectionReport,
    session_listeners: usize,
    max_connections: usize,
    connection_utilization: f64,
}

#[derive(Serialize)]
struct SourceLoadReportView {
    ccr_file: String,
    ccr_file_size_bytes: u64,
    ccr_modified_at: Option<DateTime<Tz>>,
    ccr_produced_at: Option<String>,
    slurm_enabled: bool,
    slurm_file_count: usize,
    slurm_files: Vec<String>,
    slurm_version: Option<u32>,
}

#[derive(Serialize)]
struct SourceFingerprintReport {
    ccr: FileFingerprintReport,
    slurm_files: Vec<FileFingerprintReport>,
}

impl SourceFingerprintReport {
    fn from_fingerprint(fingerprint: SourceFingerprint, timezone: Tz) -> Self {
        Self {
            ccr: FileFingerprintReport::from_fingerprint(fingerprint.ccr, timezone),
            slurm_files: fingerprint
                .slurm_files
                .into_iter()
                .map(|fingerprint| FileFingerprintReport::from_fingerprint(fingerprint, timezone))
                .collect(),
        }
    }
}

#[derive(Serialize)]
struct FileFingerprintReport {
    path: String,
    len: u64,
    modified_unix_secs: u64,
    modified_at: Option<DateTime<Tz>>,
}

impl FileFingerprintReport {
    fn from_fingerprint(fingerprint: FileFingerprint, timezone: Tz) -> Self {
        Self {
            path: fingerprint.path,
            len: fingerprint.len,
            modified_unix_secs: fingerprint.modified_unix_secs,
            modified_at: DateTime::from_timestamp(fingerprint.modified_unix_secs as i64, 0)
                .map(|time| to_report_time(time, timezone)),
        }
    }
}

impl SourceLoadReportView {
    fn from_report(report: SourceLoadReport, timezone: Tz) -> Self {
        Self {
            ccr_file: report.ccr_file,
            ccr_file_size_bytes: report.ccr_file_size_bytes,
            ccr_modified_at: report
                .ccr_modified_at
                .map(|time| to_report_time(time, timezone)),
            ccr_produced_at: report.ccr_produced_at,
            slurm_enabled: report.slurm_enabled,
            slurm_file_count: report.slurm_file_count,
            slurm_files: report.slurm_files,
            slurm_version: report.slurm_version,
        }
    }
}

#[derive(Clone, Copy, Serialize)]
struct TransportConnectionReport {
    tcp: usize,
    tls: usize,
    ssh: usize,
}

impl From<RtrTransportConnectionCounts> for TransportConnectionReport {
    fn from(counts: RtrTransportConnectionCounts) -> Self {
        Self {
            tcp: counts.tcp,
            tls: counts.tls,
            ssh: counts.ssh,
        }
    }
}

#[derive(Serialize)]
struct ProcessReport {
    rss_mib: Option<u64>,
}

#[derive(Serialize)]
struct CacheReport {
    availability: &'static str,
    created_at: DateTime<Tz>,
    last_update_begin: DateTime<Tz>,
    last_update_end: DateTime<Tz>,
    memory: CacheMemoryStats,
    versions: [VersionReportStats; 3],
}

pub fn to_report_time(time: DateTime<Utc>, timezone: Tz) -> DateTime<Tz> {
    time.with_timezone(&timezone)
}

pub fn current_rss_mib() -> Option<u64> {
    let status = fs::read_to_string("/proc/self/status").ok()?;
    let vmrss_line = status.lines().find(|line| line.starts_with("VmRSS:"))?;
    let kb = vmrss_line
        .split_whitespace()
        .nth(1)
        .and_then(|value| value.parse::<u64>().ok())?;
    Some(kb / 1024)
}

fn report_file_suffix(time: DateTime<Tz>) -> String {
    time.format("%Y%m%d%H%M%S%9f").to_string()
}

fn write_rolling_report<T: Serialize>(
    report_dir: &Path,
    prefix: &str,
    suffix: &str,
    keep: usize,
    report: &T,
) -> Result<()> {
    let file_name = format!("{prefix}-{suffix}.json");
    let target = report_dir.join(&file_name);
    let temporary = report_dir.join(format!(".{file_name}.tmp"));
    let json = serde_json::to_vec_pretty(report)
        .with_context(|| format!("serialize {prefix} RTR report"))?;
    fs::write(&temporary, json)
        .with_context(|| format!("write temporary report {}", temporary.display()))?;
    replace_file(&temporary, &target)?;
    prune_rolling_reports(report_dir, prefix, keep)?;
    Ok(())
}

fn replace_file(temporary: &Path, target: &Path) -> Result<()> {
    if let Err(err) = fs::rename(temporary, target) {
        if target.exists() {
            fs::remove_file(target)
                .with_context(|| format!("replace existing report {}", target.display()))?;
            fs::rename(temporary, target)
                .with_context(|| format!("move report into {}", target.display()))?;
        } else {
            return Err(err).with_context(|| {
                format!(
                    "move temporary report {} into {}",
                    temporary.display(),
                    target.display()
                )
            });
        }
    }
    Ok(())
}

fn prune_rolling_reports(report_dir: &Path, prefix: &str, keep: usize) -> Result<()> {
    let start = format!("{prefix}-");
    let mut files = Vec::<PathBuf>::new();
    for entry in fs::read_dir(report_dir)
        .with_context(|| format!("read report directory {}", report_dir.display()))?
    {
        let entry =
            entry.with_context(|| format!("iterate report directory {}", report_dir.display()))?;
        let path = entry.path();
        if !path.is_file() {
            continue;
        }
        let Some(name) = path.file_name().and_then(|name| name.to_str()) else {
            continue;
        };
        if name.starts_with(&start) && name.ends_with(".json") {
            files.push(path);
        }
    }
    files.sort();
    let remove_count = files.len().saturating_sub(keep);
    for path in files.into_iter().take(remove_count) {
        fs::remove_file(&path)
            .with_context(|| format!("remove old rolling report {}", path.display()))?;
    }
    Ok(())
}