use std::borrow::Cow;
use std::time::Duration;
use std::time::Instant;
use std::time::SystemTime;

use sqlx::Row;
use tokio::process::Child;
use tracing::error;

use crate::Result;
use crate::database::db_handle::DbHandle;
use crate::nix_util::nix_output_stream::NixAction;
use crate::nix_util::nix_output_stream::NixOutputStream;
use crate::nix_util::output_stream::OutputStream;
use crate::nix_util::transparent_iter::TransparentIter;

use super::activity_tree::ActivityId;
use super::activity_tree::ActivityTreeEntry;
use super::activity_tree_stream::ActivityTreeStream;
use super::nix_output_stream::ActivityResultMessage;
use super::nix_output_stream::NixMessage;

pub(crate) struct RunningBuild<'db> {
    db_handle: &'db DbHandle,
    activity_tree: ActivityTreeStream,
    last_announce: Option<Instant>,
}

impl<'db> RunningBuild<'db> {
    pub(crate) fn new(db_handle: &'db DbHandle) -> Result<Self> {
        Ok(RunningBuild {
            db_handle,
            activity_tree: ActivityTreeStream::new(),
            last_announce: None,
        })
    }

    pub(crate) async fn run_to_completion<TN>(
        &mut self,
        mut child: Child,
        target_name: TN,
    ) -> Result<()>
    where
        TN: AsRef<str>,
    {
        let foo = SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)?;
        let now = Instant::now();
        let build_id: i64 = sqlx::query(
            r#"INSERT INTO build (start_time, target) SELECT unixepoch('now'), ? RETURNING id"#,
        )
        .bind(target_name.as_ref())
        .fetch_one(&self.db_handle.conn)
        .await?
        .try_get("id")?;

        let output_stream = OutputStream::from_child(&mut child)?;
        let mut nix_output_stream: NixOutputStream<OutputStream> =
            NixOutputStream::new(output_stream);

        let exit_status_handle = tokio::spawn(async move {
            let status = child
                .wait()
                .await
                .expect("nixos-rebuild encountered an error");
            status
        });

        while let Some(message) = nix_output_stream.next().await? {
            self.handle_message(message)?;
        }

        let exit_status = exit_status_handle.await?;
        println!("nix build status was: {}", exit_status);

        let update: u64 =
            sqlx::query(r#"UPDATE build SET end_time=unixepoch('now'), status=? WHERE id=?"#)
                .bind(
                    exit_status
                        .code()
                        .expect("Process should have an exit code."),
                )
                .bind(build_id)
                .execute(&self.db_handle.conn)
                .await?
                .rows_affected();
        assert!(update == 1);

        Ok(())
    }

    pub(crate) fn handle_message(&mut self, message: NixMessage) -> Result<()> {
        self.activity_tree.handle_message(&message)?;

        let message = match message {
            NixMessage::ParseFailure(line) => {
                error!("FAIL PARSE: {line}");
                return Ok(());
            }
            NixMessage::Generic(_value, line) => {
                error!("GENERIC PARSE: {line}");
                return Ok(());
            }
            NixMessage::Action(nix_action) => nix_action,
        };
        match message {
            NixAction::Msg(msg_message) => {
                if msg_message.level > 0 && msg_message.level < 5 {
                    eprintln!("LOG MESSAGE {}: {}", msg_message.level, msg_message.msg);
                }
            }
            NixAction::Start(_activity_start_message) => {
                self.print_current_status();
            }
            NixAction::Stop(_stop_message) => {
                self.print_current_status();
                // println!("{}", serde_json::to_string(&message)?);
            }
            NixAction::Result(activity_result_message) => {
                match activity_result_message {
                    ActivityResultMessage::FileLinked(_activity_result_file_linked) => {}
                    ActivityResultMessage::BuildLogLine(_activity_result_build_log_line) => {
                        // These are the output from the actual build (as opposed to the output from nix).
                    }
                    ActivityResultMessage::UntrustedPath(_activity_result_untrusted_path) => {}
                    ActivityResultMessage::CorruptedPath(_activity_result_corrupted_path) => {}
                    ActivityResultMessage::SetPhase(_activity_result_set_phase) => {
                        self.print_current_status();
                    }
                    ActivityResultMessage::Progress(_activity_result_progress) => {
                        self.maybe_print_current_status();
                    }
                    ActivityResultMessage::SetExpected(_activity_result_set_expected) => {
                        self.maybe_print_current_status();
                    }
                    ActivityResultMessage::PostBuildLogLine(
                        _activity_result_post_build_log_line,
                    ) => {}
                    ActivityResultMessage::FetchStatus(_activity_result_fetch_status) => {}
                };
            }
        };
        Ok(())
    }

    fn maybe_print_current_status(&mut self) -> () {
        let last_announce = match self.last_announce {
            Some(instant) => instant,
            None => {
                // If we haven't announced before, always announce.
                return self.print_current_status();
            }
        };

        let now = Instant::now();
        let time_since_last_announce = now.duration_since(last_announce);
        if time_since_last_announce > Duration::new(5, 0) {
            return self.print_current_status();
        }
    }

    fn print_current_status(&mut self) -> () {
        let mut tree = String::new();
        let draw_order = self.get_draw_order();
        for dag_entry in draw_order {
            let leading_bars = {
                let mut leading_bars = String::with_capacity(3 * dag_entry.depth.len());
                for leading_bar in dag_entry
                    .depth
                    .iter()
                    .map(|depth| if *depth { "𜹈  " } else { "   " })
                {
                    leading_bars.push_str(leading_bar);
                }
                leading_bars
            };
            let branch = if dag_entry.has_later_siblings {
                "𜸨"
            } else {
                "𜸛"
            };
            let activity = self.activity_tree.get_tree().get(&dag_entry.activity_id);
            let display_name = activity
                .get_activity()
                .display_name()
                .expect("Currently we always return a display name.");
            let progress_text = activity.get_activity().get_progress_text();
            let (progress, progress_sep) = match progress_text {
                Some(text) => (text, " "),
                None => (Cow::Borrowed(""), ""),
            };
            tree += &format!("{leading_bars}{branch}𜸟 {progress}{progress_sep}{display_name}\n");
        }
        if tree.is_empty() {
            println!("No active activities.");
        } else {
            print!("\n{}\n", tree);
        }
        self.last_announce = Some(Instant::now());
    }

    fn get_draw_order(&self) -> Vec<DrawDagEntry> {
        let mut draw_order: Vec<DrawDagEntry> = Vec::new();
        let mut stack: Vec<DrawStackEntry> = self
            .get_children_in_order(self.activity_tree.get_tree().get_root_id())
            .filter_map(|child| {
                if child.get_activity().is_active() {
                    Some(DrawStackEntry::HasNotVisitedChildren(DrawDagEntry {
                        activity_id: child.get_activity_id().clone(),
                        depth: Vec::new(),
                        has_later_siblings: true,
                    }))
                } else {
                    None
                }
            })
            .collect();
        if stack.len() == 0 {
            return draw_order;
        }
        stack
            .last_mut()
            .expect("If-statement ensured this is Some()")
            .set_no_later_siblings();

        while !stack.is_empty() {
            let current_entry = stack.pop().expect("While-loop ensured this is Some.");
            match current_entry {
                DrawStackEntry::HasNotVisitedChildren(draw_dag_entry) => {
                    let current_id = draw_dag_entry.activity_id.clone();
                    let mut current_depth = draw_dag_entry.depth.clone();
                    current_depth.push(draw_dag_entry.has_later_siblings);
                    stack.push(DrawStackEntry::VisitedChildren(draw_dag_entry));
                    let children: Vec<ActivityId> = self
                        .get_children_in_order(current_id)
                        .filter_map(|child| {
                            if child.get_activity().is_active() {
                                Some(child.get_activity_id().clone())
                            } else {
                                None
                            }
                        })
                        .collect();
                    let has_children = !children.is_empty();
                    stack.extend(children.into_iter().map(|child_id| {
                        DrawStackEntry::HasNotVisitedChildren(DrawDagEntry {
                            activity_id: child_id,
                            depth: current_depth.clone(),
                            has_later_siblings: true,
                        })
                    }));
                    if has_children {
                        stack
                            .last_mut()
                            .expect("If-statement ensured this is Some()")
                            .set_no_later_siblings();
                    }
                }
                DrawStackEntry::VisitedChildren(draw_dag_entry) => {
                    draw_order.push(draw_dag_entry);
                }
            };
        }
        draw_order
    }

    fn get_children_in_order(
        &self,
        parent_id: ActivityId,
    ) -> impl Iterator<Item = &ActivityTreeEntry> {
        let parent = self.activity_tree.get_tree().get(&parent_id);
        parent
            .get_child_ids()
            .iter()
            .map(|child_id| self.activity_tree.get_tree().get(child_id))
            .flat_map(|child| TransparentIter::new(self.activity_tree.get_tree(), child))
    }
}

enum DrawStackEntry {
    HasNotVisitedChildren(DrawDagEntry),
    VisitedChildren(DrawDagEntry),
}

struct DrawDagEntry {
    activity_id: ActivityId,
    depth: Vec<bool>,
    has_later_siblings: bool,
}

impl DrawStackEntry {
    fn set_no_later_siblings(&mut self) -> () {
        match self {
            DrawStackEntry::HasNotVisitedChildren(draw_dag_entry) => {
                draw_dag_entry.has_later_siblings = false
            }
            DrawStackEntry::VisitedChildren(draw_dag_entry) => {
                draw_dag_entry.has_later_siblings = false
            }
        };
    }
}