use super::{Context, Module, RootModuleConfig, Shell};
use crate::configs::battery::BatteryConfig;

/// Creates a module for the battery percentage and charging state
pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
    // TODO: Update when v1.0 printing refactor is implemented to only
    // print escapes in a prompt context.
    let percentage_char = match context.shell {
        Shell::Zsh => "%%", // % is an escape in zsh, see PROMPT in `man zshmisc`
        _ => "%",
    };

    let battery_status = get_battery_status()?;
    let BatteryStatus { state, percentage } = battery_status;

    let mut module = context.new_module("battery");
    let battery_config: BatteryConfig = BatteryConfig::try_load(module.config);

    // Parse config under `display`
    let display_styles = &battery_config.display;
    let display_style = display_styles
        .iter()
        .find(|display_style| percentage <= display_style.threshold as f32);

    if let Some(display_style) = display_style {
        // Set style based on percentage
        module.set_style(display_style.style);
        module.get_prefix().set_value("");

        match state {
            battery::State::Full => {
                module.create_segment("full_symbol", &battery_config.full_symbol);
            }
            battery::State::Charging => {
                module.create_segment("charging_symbol", &battery_config.charging_symbol);
            }
            battery::State::Discharging => {
                module.create_segment("discharging_symbol", &battery_config.discharging_symbol);
            }
            battery::State::Unknown => {
                log::debug!("Unknown detected");
                if let Some(unknown_symbol) = battery_config.unknown_symbol {
                    module.create_segment("unknown_symbol", &unknown_symbol);
                }
            }
            battery::State::Empty => {
                if let Some(empty_symbol) = battery_config.empty_symbol {
                    module.create_segment("empty_symbol", &empty_symbol);
                }
            }
            _ => {
                log::debug!("Unhandled battery state `{}`", state);
                return None;
            }
        }

        let mut percent_string = Vec::<String>::with_capacity(2);
        // Round the percentage to a whole number
        percent_string.push(percentage.round().to_string());
        percent_string.push(percentage_char.to_string());
        module.create_segment(
            "percentage",
            &battery_config
                .percentage
                .with_value(percent_string.join("").as_ref()),
        );

        Some(module)
    } else {
        None
    }
}

fn get_battery_status() -> Option<BatteryStatus> {
    let battery_manager = battery::Manager::new().ok()?;
    let batteries = battery_manager.batteries().ok()?;
    let battery_contructor = batteries
        .filter_map(|battery| match battery {
            Ok(battery) => {
                log::debug!("Battery found: {:?}", battery);
                Some(BatteryInfo {
                    energy: battery.energy().value,
                    energy_full: battery.energy_full().value,
                    state: battery.state(),
                })
            }
            Err(e) => {
                log::debug!("Unable to access battery information:\n{}", &e);
                None
            }
        })
        .fold(
            BatteryInfo {
                energy: 0.0,
                energy_full: 0.0,
                state: battery::State::Unknown,
            },
            |mut acc, x| {
                acc.energy += x.energy;
                acc.energy_full += x.energy_full;
                acc.state = merge_battery_states(acc.state, x.state);
                acc
            },
        );
    if battery_contructor.energy_full != 0.0 {
        let battery = BatteryStatus {
            percentage: battery_contructor.energy / battery_contructor.energy_full * 100.0,
            state: battery_contructor.state,
        };
        log::debug!("Battery status: {:?}", battery);
        Some(battery)
    } else {
        None
    }
}

/// the merge returns Charging if at least one is charging
///                   Discharging if at least one is Discharging
///                   Full if both are Full or one is Full and the other Unknow
///                   Empty if both are Empty or one is Empty and the other Unknow
///                   Unknown otherwise
fn merge_battery_states(state1: battery::State, state2: battery::State) -> battery::State {
    use battery::State::{Charging, Discharging, Unknown};
    if state1 == Charging || state2 == Charging {
        Charging
    } else if state1 == Discharging || state2 == Discharging {
        Discharging
    } else if state1 == state2 {
        state1
    } else if state1 == Unknown {
        state2
    } else if state2 == Unknown {
        state1
    } else {
        Unknown
    }
}

struct BatteryInfo {
    energy: f32,
    energy_full: f32,
    state: battery::State,
}

#[derive(Debug)]
struct BatteryStatus {
    percentage: f32,
    state: battery::State,
}