use anyhow::Error;
use serde_json::json;

use handlebars::{Handlebars, Helper, Context, RenderError, RenderContext, Output, HelperResult};

use proxmox::tools::email::sendmail;
use proxmox::api::schema::parse_property_string;

use crate::{
    config::datastore::DataStoreConfig,
    config::verify::VerificationJobConfig,
    config::sync::SyncJobConfig,
    api2::types::{
        APTUpdateInfo,
        GarbageCollectionStatus,
        Userid,
        Notify,
        DatastoreNotify,
    },
    tools::format::HumanByte,
};

const GC_OK_TEMPLATE: &str = r###"

Datastore:            {{datastore}}
Task ID:              {{status.upid}}
Index file count:     {{status.index-file-count}}

Removed garbage:      {{human-bytes status.removed-bytes}}
Removed chunks:       {{status.removed-chunks}}
Removed bad chunks:   {{status.removed-bad}}

Leftover bad chunks:  {{status.still-bad}}
Pending removals:     {{human-bytes status.pending-bytes}} (in {{status.pending-chunks}} chunks)

Original Data usage:  {{human-bytes status.index-data-bytes}}
On-Disk usage:        {{human-bytes status.disk-bytes}} ({{relative-percentage status.disk-bytes status.index-data-bytes}})
On-Disk chunks:       {{status.disk-chunks}}

Deduplication Factor: {{deduplication-factor}}

Garbage collection successful.


Please visit the web interface for futher details:

<https://{{fqdn}}:{{port}}/#DataStore-{{datastore}}>

"###;


const GC_ERR_TEMPLATE: &str = r###"

Datastore: {{datastore}}

Garbage collection failed: {{error}}


Please visit the web interface for futher details:

<https://{{fqdn}}:{{port}}/#pbsServerAdministration:tasks>

"###;

const VERIFY_OK_TEMPLATE: &str = r###"

Job ID:    {{job.id}}
Datastore: {{job.store}}

Verification successful.


Please visit the web interface for futher details:

<https://{{fqdn}}:{{port}}/#DataStore-{{job.store}}>

"###;

const VERIFY_ERR_TEMPLATE: &str = r###"

Job ID:    {{job.id}}
Datastore: {{job.store}}

Verification failed on these snapshots:

{{#each errors}}
  {{this~}}
{{/each}}


Please visit the web interface for futher details:

<https://{{fqdn}}:{{port}}/#pbsServerAdministration:tasks>

"###;

const SYNC_OK_TEMPLATE: &str = r###"

Job ID:       {{job.id}}
Datastore:    {{job.store}}
Remote:       {{job.remote}}
Remote Store: {{job.remote-store}}

Synchronization successful.


Please visit the web interface for futher details:

<https://{{fqdn}}:{{port}}/#DataStore-{{job.store}}>

"###;

const SYNC_ERR_TEMPLATE: &str = r###"

Job ID:       {{job.id}}
Datastore:    {{job.store}}
Remote:       {{job.remote}}
Remote Store: {{job.remote-store}}

Synchronization failed: {{error}}


Please visit the web interface for futher details:

<https://{{fqdn}}:{{port}}/#pbsServerAdministration:tasks>

"###;

const PACKAGE_UPDATES_TEMPLATE: &str = r###"
Proxmox Backup Server has the following updates available:
{{#each updates }}
  {{Package}}: {{OldVersion}} -> {{Version~}}
{{/each }}

To upgrade visit the web interface:

<https://{{fqdn}}:{{port}}/#pbsServerAdministration:updates>

"###;


lazy_static::lazy_static!{

    static ref HANDLEBARS: Handlebars<'static> = {
        let mut hb = Handlebars::new();

        hb.set_strict_mode(true);

        hb.register_helper("human-bytes", Box::new(handlebars_humam_bytes_helper));
        hb.register_helper("relative-percentage", Box::new(handlebars_relative_percentage_helper));

        hb.register_template_string("gc_ok_template", GC_OK_TEMPLATE).unwrap();
        hb.register_template_string("gc_err_template", GC_ERR_TEMPLATE).unwrap();

        hb.register_template_string("verify_ok_template", VERIFY_OK_TEMPLATE).unwrap();
        hb.register_template_string("verify_err_template", VERIFY_ERR_TEMPLATE).unwrap();

        hb.register_template_string("sync_ok_template", SYNC_OK_TEMPLATE).unwrap();
        hb.register_template_string("sync_err_template", SYNC_ERR_TEMPLATE).unwrap();

        hb.register_template_string("package_update_template", PACKAGE_UPDATES_TEMPLATE).unwrap();

        hb
    };
}

fn send_job_status_mail(
    email: &str,
    subject: &str,
    text: &str,
) -> Result<(), Error> {

    // Note: OX has serious problems displaying text mails,
    // so we include html as well
    let html = format!("<html><body><pre>\n{}\n<pre>", handlebars::html_escape(text));

    let nodename = proxmox::tools::nodename();

    let author = format!("Proxmox Backup Server - {}", nodename);

    sendmail(
        &[email],
        &subject,
        Some(&text),
        Some(&html),
        None,
        Some(&author),
    )?;

    Ok(())
}

pub fn send_gc_status(
    email: &str,
    notify: DatastoreNotify,
    datastore: &str,
    status: &GarbageCollectionStatus,
    result: &Result<(), Error>,
) -> Result<(), Error> {

    match notify.gc {
        None => { /* send notifications by default */ },
        Some(notify) => {
            if notify == Notify::Never || (result.is_ok() && notify == Notify::Error) {
                return Ok(());
            }
        }
    }

    let (fqdn, port) = get_server_url();
    let mut data = json!({
        "datastore": datastore,
        "fqdn": fqdn,
        "port": port,
    });

    let text = match result {
        Ok(()) => {
            let deduplication_factor = if status.disk_bytes > 0 {
                (status.index_data_bytes as f64)/(status.disk_bytes as f64)
            } else {
                1.0
            };

            data["status"] = json!(status);
            data["deduplication-factor"] = format!("{:.2}", deduplication_factor).into();

            HANDLEBARS.render("gc_ok_template", &data)?
        }
        Err(err) => {
            data["error"] = err.to_string().into();
            HANDLEBARS.render("gc_err_template", &data)?
        }
    };

    let subject = match result {
        Ok(()) => format!(
            "Garbage Collect Datastore '{}' successful",
            datastore,
        ),
        Err(_) => format!(
            "Garbage Collect Datastore '{}' failed",
            datastore,
        ),
    };

    send_job_status_mail(email, &subject, &text)?;

    Ok(())
}

pub fn send_verify_status(
    email: &str,
    notify: DatastoreNotify,
    job: VerificationJobConfig,
    result: &Result<Vec<String>, Error>,
) -> Result<(), Error> {

    let (fqdn, port) = get_server_url();
    let mut data = json!({
        "job": job,
        "fqdn": fqdn,
        "port": port,
    });

    let mut result_is_ok = false;

    let text = match result {
        Ok(errors) if errors.is_empty() => {
            result_is_ok = true;
            HANDLEBARS.render("verify_ok_template", &data)?
        }
        Ok(errors) => {
            data["errors"] = json!(errors);
            HANDLEBARS.render("verify_err_template", &data)?
        }
        Err(_) => {
            // aborted job - do not send any email
            return Ok(());
        }
    };

    match notify.verify {
        None => { /* send notifications by default */ },
        Some(notify) => {
            if notify == Notify::Never || (result_is_ok && notify == Notify::Error) {
                return Ok(());
            }
        }
    }

    let subject = match result {
        Ok(errors) if errors.is_empty() => format!(
            "Verify Datastore '{}' successful",
            job.store,
        ),
        _ => format!(
            "Verify Datastore '{}' failed",
            job.store,
        ),
    };

    send_job_status_mail(email, &subject, &text)?;

    Ok(())
}

pub fn send_sync_status(
    email: &str,
    notify: DatastoreNotify,
    job: &SyncJobConfig,
    result: &Result<(), Error>,
) -> Result<(), Error> {

    match notify.sync {
        None => { /* send notifications by default */ },
        Some(notify) => {
            if notify == Notify::Never || (result.is_ok() && notify == Notify::Error) {
                return Ok(());
            }
        }
    }

    let (fqdn, port) = get_server_url();
    let mut data = json!({
        "job": job,
        "fqdn": fqdn,
        "port": port,
    });

    let text = match result {
        Ok(()) => {
            HANDLEBARS.render("sync_ok_template", &data)?
        }
        Err(err) => {
            data["error"] = err.to_string().into();
            HANDLEBARS.render("sync_err_template", &data)?
        }
    };

    let subject = match result {
        Ok(()) => format!(
            "Sync remote '{}' datastore '{}' successful",
            job.remote,
            job.remote_store,
        ),
        Err(_) => format!(
            "Sync remote '{}' datastore '{}' failed",
            job.remote,
            job.remote_store,
        ),
    };

    send_job_status_mail(email, &subject, &text)?;

    Ok(())
}

fn get_server_url() -> (String, usize) {

    // user will surely request that they can change this

    let nodename = proxmox::tools::nodename();
    let mut fqdn = nodename.to_owned();

    if let Ok(resolv_conf) = crate::api2::node::dns::read_etc_resolv_conf() {
        if let Some(search) = resolv_conf["search"].as_str() {
            fqdn.push('.');
            fqdn.push_str(search);
        }
    }

    let port = 8007;

    (fqdn, port)
}

pub fn send_updates_available(
    updates: &Vec<&APTUpdateInfo>,
) -> Result<(), Error> {
    // update mails always go to the root@pam configured email..
    if let Some(email) = lookup_user_email(Userid::root_userid()) {
        let nodename = proxmox::tools::nodename();
        let subject = format!("New software packages available ({})", nodename);

        let (fqdn, port) = get_server_url();

        let text = HANDLEBARS.render("package_update_template", &json!({
            "fqdn": fqdn,
            "port": port,
            "updates": updates,
        }))?;

        send_job_status_mail(&email, &subject, &text)?;
    }
    Ok(())
}

/// Lookup users email address
///
/// For "backup@pam", this returns the address from "root@pam".
fn lookup_user_email(userid: &Userid) -> Option<String> {

    use crate::config::user::{self, User};

    if userid == Userid::backup_userid() {
        return lookup_user_email(Userid::root_userid());
    }

    if let Ok(user_config) = user::cached_config() {
        if let Ok(user) = user_config.lookup::<User>("user", userid.as_str()) {
            return user.email.clone();
        }
    }

    None
}

/// Lookup Datastore notify settings
pub fn lookup_datastore_notify_settings(
    store: &str,
) -> (Option<String>, DatastoreNotify) {

    let mut email = None;

    let notify = DatastoreNotify { gc: None, verify: None, sync: None };

    let (config, _digest) = match crate::config::datastore::config() {
        Ok(result) => result,
        Err(_) => return (email, notify),
    };

    let config: DataStoreConfig = match config.lookup("datastore", store) {
        Ok(result) => result,
        Err(_) => return (email, notify),
    };

    email = match config.notify_user {
        Some(ref userid) => lookup_user_email(userid),
        None => lookup_user_email(Userid::backup_userid()),
    };

    let notify_str = config.notify.unwrap_or(String::new());

    if let Ok(value) = parse_property_string(&notify_str, &DatastoreNotify::API_SCHEMA) {
        if let Ok(notify) = serde_json::from_value(value) {
            return (email, notify);
        }
    }

    (email, notify)
}

// Handlerbar helper functions

fn handlebars_humam_bytes_helper(
    h: &Helper,
    _: &Handlebars,
    _: &Context,
    _rc: &mut RenderContext,
    out: &mut dyn Output
) -> HelperResult {
    let param = h.param(0).map(|v| v.value().as_u64())
        .flatten()
        .ok_or(RenderError::new("human-bytes: param not found"))?;

    out.write(&HumanByte::from(param).to_string())?;

    Ok(())
}

fn handlebars_relative_percentage_helper(
    h: &Helper,
    _: &Handlebars,
    _: &Context,
    _rc: &mut RenderContext,
    out: &mut dyn Output
) -> HelperResult {
    let param0 = h.param(0).map(|v| v.value().as_f64())
        .flatten()
        .ok_or(RenderError::new("relative-percentage: param0 not found"))?;
    let param1 = h.param(1).map(|v| v.value().as_f64())
        .flatten()
        .ok_or(RenderError::new("relative-percentage: param1 not found"))?;

    if param1 == 0.0 {
        out.write("-")?;
    } else {
        out.write(&format!("{:.2}%", (param0*100.0)/param1))?;
    }
    Ok(())
}