use std::collections::HashMap;
use std::io::Write;
use std::time::SystemTime;

use crate::core::process::Pid;
use crate::core::types::{StackFrame, StackTrace};

use anyhow::Result;

/*
 * This file contains code to export rbspy profiles for use in https://speedscope.app
 *
 * The TypeScript definitions that define this file format can be found here:
 * https://github.com/jlfwong/speedscope/blob/9d13d9/src/lib/file-format-spec.ts
 *
 * From the TypeScript definition, a JSON schema is generated. The latest
 * schema can be found here: https://speedscope.app/file-format-schema.json
 *
 * This JSON schema conveniently allows to generate type bindings for generating JSON.
 * You can use https://app.quicktype.io/ to generate serde_json Rust bindings for the
 * given JSON schema.
 *
 * There are multiple variants of the file format. The variant we're going to generate
 * is the "type: sampled" profile, since it most closely maps to rbspy's data recording
 * structure.
 */

#[derive(Debug, Serialize, Deserialize)]
struct SpeedscopeFile {
    #[serde(rename = "$schema")]
    schema: String,
    profiles: Vec<Profile>,
    shared: Shared,

    #[serde(rename = "activeProfileIndex")]
    active_profile_index: Option<f64>,

    exporter: Option<String>,

    name: Option<String>,
}

#[derive(Debug, Serialize, Deserialize)]
struct Profile {
    #[serde(rename = "type")]
    profile_type: ProfileType,

    name: String,
    unit: ValueUnit,

    #[serde(rename = "startValue")]
    start_value: f64,

    #[serde(rename = "endValue")]
    end_value: f64,

    samples: Vec<Vec<usize>>,
    weights: Vec<f64>,
}

#[derive(Debug, Serialize, Deserialize)]
struct Shared {
    frames: Vec<Frame>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
struct Frame {
    name: String,
    file: Option<String>,
    line: Option<u32>,
    col: Option<u32>,
}

#[derive(Debug, Serialize, Deserialize)]
enum ProfileType {
    #[serde(rename = "evented")]
    Evented,
    #[serde(rename = "sampled")]
    Sampled,
}

#[derive(Debug, Serialize, Deserialize)]
enum ValueUnit {
    #[serde(rename = "bytes")]
    Bytes,
    #[serde(rename = "microseconds")]
    Microseconds,
    #[serde(rename = "milliseconds")]
    Milliseconds,
    #[serde(rename = "nanoseconds")]
    Nanoseconds,
    #[serde(rename = "none")]
    None,
    #[serde(rename = "seconds")]
    Seconds,
}

impl SpeedscopeFile {
    pub fn new(
        samples: HashMap<Option<Pid>, Vec<Vec<usize>>>,
        frames: Vec<Frame>,
        weights: Vec<f64>,
    ) -> SpeedscopeFile {
        let end_value = samples.len();

        SpeedscopeFile {
            // This is always the same
            schema: "https://www.speedscope.app/file-format-schema.json".to_string(),

            active_profile_index: None,

            name: Some("rbspy profile".to_string()),

            exporter: Some(format!("rbspy@{}", env!("CARGO_PKG_VERSION"))),

            profiles: samples
                .iter()
                .map(|(option_pid, samples)| Profile {
                    profile_type: ProfileType::Sampled,

                    name: option_pid.map_or("rbspy profile".to_string(), |pid| {
                        format!("rbspy profile - pid {}", pid)
                    }),

                    unit: ValueUnit::Seconds,

                    start_value: 0.0,
                    end_value: end_value as f64,

                    samples: samples.clone(),
                    weights: weights.clone(),
                })
                .collect(),

            shared: Shared { frames },
        }
    }
}

impl Frame {
    pub fn new(stack_frame: &StackFrame) -> Frame {
        Frame {
            name: stack_frame.name.clone(),
            file: Some(stack_frame.relative_path.clone()),
            line: Some(stack_frame.lineno),
            col: None,
        }
    }
}

#[derive(Default)]
pub struct Stats {
    samples: HashMap<Option<Pid>, Vec<Vec<usize>>>,
    frames: Vec<Frame>,
    frame_to_index: HashMap<StackFrame, usize>,
    weights: Vec<f64>,
    prev_time: Option<SystemTime>,
}

impl Stats {
    pub fn new() -> Stats {
        Default::default()
    }

    pub fn record(&mut self, stack: &StackTrace) -> Result<()> {
        let mut frame_indices: Vec<usize> = stack
            .trace
            .iter()
            .map(|frame| {
                let frames = &mut self.frames;
                *self.frame_to_index.entry(frame.clone()).or_insert_with(|| {
                    let len = frames.len();
                    frames.push(Frame::new(&frame));
                    len
                })
            })
            .collect();
        frame_indices.reverse();

        self.samples
            .entry(stack.pid)
            .or_insert_with(|| vec![])
            .push(frame_indices);

        if let Some(time) = stack.time {
            if let Some(prev_time) = self.prev_time {
                let delta = time.duration_since(prev_time)?;
                self.weights.push(delta.as_secs_f64());
            } else {
                // drop first sample, since we have no delta to compare against
                self.weights.push(0.0);
            }
            self.prev_time = stack.time;
        } else {
            // support for import from old profiles that have no timestamps
            self.weights.push(1.0);
        }

        Ok(())
    }

    pub fn write(&self, mut w: &mut dyn Write) -> Result<()> {
        let json = serde_json::to_string(&SpeedscopeFile::new(
            self.samples.clone(),
            self.frames.clone(),
            self.weights.clone(),
        ))?;
        writeln!(&mut w, "{}", json)?;
        Ok(())
    }
}