use crate::config::Config;
use chrono::{Datelike, Timelike};
use serde::{Deserialize, Serialize};
use std::time::Instant;

#[derive(Debug, Clone, Copy, PartialEq, Serialize)]
#[serde(rename_all = "camelCase")]
pub enum TimerState {
    Running,
    Paused,
    BreakActive,
}

impl Default for TimerState {
    fn default() -> Self {
        Self::Paused
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub enum AppView {
    Dashboard,
    BreakScreen,
    Settings,
    Stats,
}

/// Snapshot of the full timer state, sent to the frontend on every tick
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct TimerSnapshot {
    pub state: TimerState,
    pub current_view: AppView,
    pub time_remaining: u64,
    pub total_duration: u64,
    pub progress: f64,
    pub has_had_break: bool,
    pub seconds_since_last_break: u64,
    pub prebreak_warning: bool,
    pub snoozes_used: u32,
    pub can_snooze: bool,
    pub break_title: String,
    pub break_message: String,
    pub break_progress: f64,
    pub break_time_remaining: u64,
    pub break_total_duration: u64,
    pub break_past_half: bool,
    pub settings_modified: bool,
    pub idle_paused: bool,
    pub natural_break_occurred: bool,
    pub smart_breaks_enabled: bool,
    pub smart_break_threshold: u32,
}

/// Events emitted by the timer to the frontend
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct BreakStartedPayload {
    pub title: String,
    pub message: String,
    pub duration: u64,
    pub strict_mode: bool,
    pub snooze_duration: u32,
    pub fullscreen_mode: bool,
}

pub struct TimerManager {
    pub state: TimerState,
    pub current_view: AppView,
    pub config: Config,
    pub time_until_next_break: u64,
    pub time_until_break_end: u64,
    pub break_total_duration: u64,
    pub snoozes_used: u32,
    pub seconds_since_last_break: u64,
    pub has_had_break: bool,
    pub prebreak_notification_active: bool,
    pub settings_modified: bool,
    // Pending config: edited in settings but not yet saved
    pub pending_config: Config,
    // Idle detection: true when auto-paused due to inactivity
    pub idle_paused: bool,
    // Smart breaks: track when idle started for natural break detection
    pub idle_start_time: Option<Instant>,
    pub natural_break_occurred: bool,
}

impl TimerManager {
    pub fn new() -> Self {
        let config = Config::load_or_default();
        let freq = config.break_frequency_seconds();
        let pending = config.clone();
        let auto_start = config.auto_start;

        Self {
            state: if auto_start {
                TimerState::Running
            } else {
                TimerState::Paused
            },
            current_view: AppView::Dashboard,
            config,
            time_until_next_break: freq,
            time_until_break_end: 0,
            break_total_duration: 0,
            snoozes_used: 0,
            seconds_since_last_break: 0,
            has_had_break: false,
            prebreak_notification_active: false,
            settings_modified: false,
            pending_config: pending,
            idle_paused: false,
            idle_start_time: None,
            natural_break_occurred: false,
        }
    }

    /// Check idle state and auto-pause/resume accordingly.
    /// Returns IdleCheckResult indicating what happened.
    pub fn check_idle(&mut self) -> IdleCheckResult {
        if !self.config.idle_detection_enabled {
            // If idle detection disabled but we were idle-paused, resume
            if self.idle_paused {
                self.idle_paused = false;
                self.state = TimerState::Running;
            }
            return IdleCheckResult::None;
        }

        let idle_secs = get_idle_seconds();
        let threshold = self.config.idle_timeout as u64;

        if idle_secs >= threshold && self.state == TimerState::Running {
            // Just became idle - record start time for smart breaks
            if self.idle_start_time.is_none() {
                self.idle_start_time = Some(Instant::now());
            }
            self.idle_paused = true;
            self.state = TimerState::Paused;
            IdleCheckResult::JustPaused
        } else if idle_secs < threshold && self.idle_paused {
            // Just returned from idle
            self.idle_paused = false;
            self.state = TimerState::Running;

            // Check if this was a natural break
            if let Some(start_time) = self.idle_start_time {
                let idle_duration = start_time.elapsed().as_secs();
                self.idle_start_time = None;

                if self.config.smart_breaks_enabled
                    && self.state != TimerState::BreakActive
                    && idle_duration >= self.config.smart_break_threshold as u64
                {
                    // Natural break detected!
                    return IdleCheckResult::NaturalBreakDetected(idle_duration);
                }
            }

            IdleCheckResult::JustResumed
        } else {
            // Still idle - update idle_start_time if needed
            if self.state == TimerState::Paused
                && self.idle_start_time.is_none()
                && idle_secs >= threshold
            {
                // We were already paused when idle detection kicked in
                // Start tracking from now
                self.idle_start_time = Some(Instant::now());
            }
            IdleCheckResult::None
        }
    }

    /// Called every second. Returns what events should be emitted.
    pub fn tick(&mut self) -> TickResult {
        // Idle detection and natural break detection
        let idle_result = self.check_idle();

        // Handle natural break detection
        if let IdleCheckResult::NaturalBreakDetected(duration) = idle_result {
            // Reset the timer completely since they took a natural break
            self.reset_timer();
            self.has_had_break = true;
            self.seconds_since_last_break = 0;
            self.natural_break_occurred = true;
            return TickResult::NaturalBreakDetected {
                duration_seconds: duration,
            };
        }

        // Track time since last break (always, even when paused)
        if self.has_had_break && self.state != TimerState::BreakActive {
            self.seconds_since_last_break += 1;
        }

        match self.state {
            TimerState::Running => {
                if !self.is_within_working_hours() {
                    return TickResult::None;
                }

                // Pre-break notification
                let threshold = self.config.notification_before_break as u64;
                let fire_prebreak = self.config.notification_enabled
                    && !self.config.immediately_start_breaks
                    && threshold > 0
                    && self.time_until_next_break <= threshold
                    && !self.prebreak_notification_active;

                if fire_prebreak {
                    self.prebreak_notification_active = true;
                }

                if self.time_until_next_break > 0 {
                    self.time_until_next_break -= 1;
                    if fire_prebreak {
                        TickResult::PreBreakWarning {
                            seconds_until_break: self.time_until_next_break,
                        }
                    } else {
                        TickResult::None
                    }
                } else {
                    self.start_break();
                    TickResult::BreakStarted(BreakStartedPayload {
                        title: self.config.break_title.clone(),
                        message: self.config.break_message.clone(),
                        duration: self.break_total_duration,
                        strict_mode: self.config.strict_mode,
                        snooze_duration: self.config.snooze_duration,
                        fullscreen_mode: self.config.fullscreen_mode,
                    })
                }
            }
            TimerState::BreakActive => {
                if self.time_until_break_end > 0 {
                    self.time_until_break_end -= 1;
                    TickResult::None
                } else {
                    // Break completed naturally
                    self.has_had_break = true;
                    self.seconds_since_last_break = 0;
                    self.reset_timer();
                    TickResult::BreakEnded
                }
            }
            TimerState::Paused => TickResult::None,
        }
    }

    pub fn start_break(&mut self) {
        self.state = TimerState::BreakActive;
        self.current_view = AppView::BreakScreen;
        self.break_total_duration = self.config.break_duration_seconds();
        self.time_until_break_end = self.break_total_duration;
        self.prebreak_notification_active = false;
        self.snoozes_used = 0;
    }

    pub fn reset_timer(&mut self) {
        self.state = TimerState::Running;
        self.current_view = AppView::Dashboard;
        self.time_until_next_break = self.config.break_frequency_seconds();
        self.prebreak_notification_active = false;
    }

    pub fn toggle_timer(&mut self) {
        match self.state {
            TimerState::Running => {
                self.state = TimerState::Paused;
            }
            TimerState::Paused => {
                self.state = TimerState::Running;
            }
            _ => {}
        }
    }

    pub fn start_break_now(&mut self) -> Option<BreakStartedPayload> {
        if self.state == TimerState::Running || self.state == TimerState::Paused {
            self.start_break();
            Some(BreakStartedPayload {
                title: self.config.break_title.clone(),
                message: self.config.break_message.clone(),
                duration: self.break_total_duration,
                strict_mode: self.config.strict_mode,
                snooze_duration: self.config.snooze_duration,
                fullscreen_mode: self.config.fullscreen_mode,
            })
        } else {
            None
        }
    }

    pub fn cancel_break(&mut self) -> bool {
        if self.state != TimerState::BreakActive {
            return false;
        }

        if self.config.strict_mode {
            return false;
        }

        let total = self.break_total_duration;
        let elapsed = total.saturating_sub(self.time_until_break_end);
        let past_half = total > 0 && elapsed * 2 >= total;

        if past_half && self.config.allow_end_early {
            // "End break" — counts as completed
            self.has_had_break = true;
            self.seconds_since_last_break = 0;
            self.reset_timer();
            true
        } else if !past_half {
            // "Cancel break" — doesn't count
            self.reset_timer();
            true
        } else {
            false
        }
    }

    pub fn snooze(&mut self) -> bool {
        if self.config.strict_mode || !self.can_snooze() {
            return false;
        }

        self.snoozes_used += 1;
        self.time_until_next_break = self.config.snooze_duration_seconds();
        self.state = TimerState::Running;
        self.current_view = AppView::Dashboard;
        self.prebreak_notification_active = false;
        true
    }

    pub fn can_snooze(&self) -> bool {
        if self.config.snooze_limit == 0 {
            return true; // unlimited
        }
        self.snoozes_used < self.config.snooze_limit
    }

    pub fn is_within_working_hours(&self) -> bool {
        if !self.config.working_hours_enabled {
            return true;
        }

        let now = chrono::Local::now();
        let day_of_week = now.weekday().num_days_from_monday() as usize; // 0 = Monday, 6 = Sunday
        let current_minutes = now.hour() * 60 + now.minute();

        // Get the schedule for today
        if let Some(day_schedule) = self.config.working_hours_schedule.get(day_of_week) {
            if !day_schedule.enabled {
                return false; // Day is disabled, timer doesn't run
            }

            // Check if current time falls within any of the time ranges
            for range in &day_schedule.ranges {
                let start_mins = Config::time_to_minutes(&range.start);
                let end_mins = Config::time_to_minutes(&range.end);

                if current_minutes >= start_mins && current_minutes < end_mins {
                    return true;
                }
            }
        }

        false // Not within any time range
    }

    pub fn set_view(&mut self, view: AppView) {
        self.current_view = view;
    }

    pub fn update_config(&mut self, config: Config) {
        self.pending_config = config;
        self.settings_modified = true;
    }

    pub fn save_config(&mut self) -> Result<(), String> {
        let validated = self.pending_config.clone().validate();
        validated.save().map_err(|e| e.to_string())?;
        self.config = validated.clone();
        self.pending_config = validated;
        self.settings_modified = false;
        Ok(())
    }

    pub fn reset_config(&mut self) {
        self.pending_config = Config::default();
        self.settings_modified = true;
    }

    pub fn snapshot(&self) -> TimerSnapshot {
        let total_freq = self.config.break_frequency_seconds();
        let timer_progress = if total_freq > 0 {
            self.time_until_next_break as f64 / total_freq as f64
        } else {
            0.0
        };

        let break_elapsed = self
            .break_total_duration
            .saturating_sub(self.time_until_break_end);
        let break_progress = if self.break_total_duration > 0 {
            break_elapsed as f64 / self.break_total_duration as f64
        } else {
            0.0
        };
        let break_past_half =
            self.break_total_duration > 0 && break_elapsed * 2 >= self.break_total_duration;

        // Use pending_config for settings display, active config for timer
        let display_config = if self.current_view == AppView::Settings {
            &self.pending_config
        } else {
            &self.config
        };

        TimerSnapshot {
            state: self.state,
            current_view: self.current_view,
            time_remaining: self.time_until_next_break,
            total_duration: total_freq,
            progress: timer_progress,
            has_had_break: self.has_had_break,
            seconds_since_last_break: self.seconds_since_last_break,
            prebreak_warning: self.prebreak_notification_active,
            snoozes_used: self.snoozes_used,
            can_snooze: self.can_snooze(),
            break_title: display_config.break_title.clone(),
            break_message: display_config.break_message.clone(),
            break_progress,
            break_time_remaining: self.time_until_break_end,
            break_total_duration: self.break_total_duration,
            break_past_half,
            settings_modified: self.settings_modified,
            idle_paused: self.idle_paused,
            natural_break_occurred: self.natural_break_occurred,
            smart_breaks_enabled: display_config.smart_breaks_enabled,
            smart_break_threshold: display_config.smart_break_threshold,
        }
    }
}

pub enum TickResult {
    None,
    BreakStarted(BreakStartedPayload),
    BreakEnded,
    PreBreakWarning { seconds_until_break: u64 },
    NaturalBreakDetected { duration_seconds: u64 },
}

/// Result of checking idle state
pub enum IdleCheckResult {
    None,
    JustPaused,
    JustResumed,
    NaturalBreakDetected(u64), // duration in seconds
}

fn parse_hour(time_str: &str) -> u32 {
    time_str
        .split(':')
        .next()
        .and_then(|h| h.parse().ok())
        .unwrap_or(9)
}

/// Returns the number of seconds since last user input (mouse/keyboard).
#[cfg(windows)]
pub fn get_idle_seconds() -> u64 {
    use std::mem;
    use winapi::um::sysinfoapi::GetTickCount;
    use winapi::um::winuser::{GetLastInputInfo, LASTINPUTINFO};

    unsafe {
        let mut lii: LASTINPUTINFO = mem::zeroed();
        lii.cbSize = mem::size_of::<LASTINPUTINFO>() as u32;
        if GetLastInputInfo(&mut lii) != 0 {
            let tick = GetTickCount();
            let idle_ms = tick.wrapping_sub(lii.dwTime);
            (idle_ms / 1000) as u64
        } else {
            0
        }
    }
}

#[cfg(not(windows))]
pub fn get_idle_seconds() -> u64 {
    0
}