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use std::time::Instant;
#[derive(Debug)]

/// This is is one and the only struct we need and have.
/// We do not need to make any of its members public.
pub struct PlayHead {
    old_time:u128,
    paused:bool,
    time_lapsed:Instant, 
}

impl PlayHead {
    pub fn new()->Self{
        ///it must start paused since "first play" or any "play after pause" is the same.
        PlayHead  { 
            paused:true, 
            old_time: 0,
            time_lapsed :  Instant::now(),//start time
        }
    }
     
    ///- There is no diff bw first play and play after pause 
    ///- Here we can just set paused to false and thats it
    ///- We can be in either paused mode or play mode, there are just /these 2 states, there is no third state for play head.
    ///- The time is the time spent in play mode excluding the time spent ///in pause mode.
        
    pub fn play(&mut self)->bool{
        if self.paused == true{
            self.time_lapsed =  Instant::now();
            self.paused = false;
        }      
        true
    }
    pub fn time(&self)->u128{ 
        if self.paused == false{
            self.time_lapsed.elapsed().as_millis() + self.old_time                    
         }else {
            self.old_time
        } 
    }
    
    /// - pause fn is used to pause the counter and before that add the ///current time into old_time.
    /// - the lapsed_time will not be added again if pause is called ///twice since the old_time is updated only when pause is false. ///once it is true the code inside will not run. to make it false ///again we have to go through play.
    /// - here we can just set pause to true and nothing more. 
     
    pub fn pause (&mut self)->bool{
        if self.paused == false{ 
            self.old_time += self.time_lapsed.elapsed().as_millis();
            self.paused = true;
        }
           true   
    }
    pub fn stop(&mut self)->bool{
        self.paused = true;
        self.old_time = 0;
        true
    }

}//playHead impl ends