use std::{num::ParseFloatError, str::FromStr};


use serde::{Deserialize, Serialize};

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
pub struct Timestamp {
    hour: u8,
    minute: u8,
    second: u8,
    frame: u8,
}

#[derive(Debug)]
pub enum TimestampParseError {
    EmptyTimestamp,
    TooManySegments,
    NumberParseError(ParseFloatError, String),
}

impl std::fmt::Display for TimestampParseError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&format!("{self:?}"))
    }
}

impl std::error::Error for TimestampParseError {}

impl FromStr for Timestamp {
    type Err = TimestampParseError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let s = s.trim();
        if s.is_empty() {
            return Err(TimestampParseError::EmptyTimestamp);
        }

        let mut segments = s.split(':').collect::<Vec<_>>();
        if segments.len() > 4 {
            return Err(TimestampParseError::TooManySegments);
        }

        segments.reverse();

        let Some(frame) = segments.first() else {
            return Err(TimestampParseError::EmptyTimestamp);
        };

        let frame = frame.parse::<f32>().map(|v| v.floor() as u8).map_err(|e| {
            TimestampParseError::NumberParseError(e, format!("frame failed for {s}"))
        })?;
        let second = segments
            .get(1)
            .unwrap_or(&"0")
            .parse::<f32>()
            .map(|v| v.floor() as u8)
            .map_err(|e| {
                TimestampParseError::NumberParseError(e, format!("second failed for {s}"))
            })?;
        let minute = segments
            .get(2)
            .unwrap_or(&"0")
            .parse::<f32>()
            .map(|v| v.floor() as u8)
            .map_err(|e| {
                TimestampParseError::NumberParseError(e, format!("minute failed for {s}"))
            })?;
        let hour = segments
            .get(3)
            .unwrap_or(&"0")
            .parse::<f32>()
            .map(|v| v.floor() as u8)
            .map_err(|e| {
                TimestampParseError::NumberParseError(e, format!("hour failed for {s}"))
            })?;

        Ok(Self {
            hour,
            minute,
            second,
            frame,
        })
    }
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
pub struct CSVFrame {
    pub timestamp: Timestamp,
    pub morphs: Vec<f32>,
}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct CSVAnimation {
    pub frames: Vec<CSVFrame>,
    pub morph_names: Vec<String>,
    pub fps: u8,
}

#[derive(Debug)]
pub enum CSVParseError {
    NoData,
    InvalidCSV(csv::Error),
    NoMorphs,
    MisssingKnownHeaders,
    NoFrames,
    TimecodeParseError(TimestampParseError),
    MorphParseError(ParseFloatError),
}

impl std::fmt::Display for CSVParseError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&format!("{self:?}"))
    }
}

impl std::error::Error for CSVParseError {}

const SKIP_COLUMNS_BEFORE_MORPH: usize = 1;

impl CSVAnimation {
    pub fn parse(csv: &str) -> Result<CSVAnimation, CSVParseError> {
        if csv.is_empty() {
            return Err(CSVParseError::NoData);
        }

        let buffer = csv.as_bytes();

        let mut csv_content = csv::ReaderBuilder::new()
            .has_headers(false)
            .from_reader(buffer);

        let mut records = csv_content.records();

        let header_row = records
            .next()
            .ok_or(CSVParseError::NoData)?
            .map_err(CSVParseError::InvalidCSV)?;

        let morph_names: Vec<String> = header_row
            .iter()
            .enumerate()
            .filter_map(|(i, v)| {
                if i > SKIP_COLUMNS_BEFORE_MORPH {
                    Some(v.trim().to_string())
                } else {
                    None
                }
            })
            .collect();

        if morph_names.is_empty() {
            return Err(CSVParseError::NoMorphs);
        }

        let mut frames = Vec::new();
        let mut fps: u8 = 0;

        for result in records {
            let record = result.map_err(CSVParseError::InvalidCSV)?;

            let mut iter = record.iter();

            let timestamp = iter.next().ok_or(CSVParseError::MisssingKnownHeaders)?; // This error should be impossible since the CSV parser validates that all rows have the same length, and we already confirmed there is more than 0 characters in the first row.
            let timestamp: Timestamp = timestamp
                .parse()
                .map_err(CSVParseError::TimecodeParseError)?;
            for _ in 0..SKIP_COLUMNS_BEFORE_MORPH {
                let _ = iter.next().ok_or(CSVParseError::MisssingKnownHeaders)?;
                // similarly, we already validate that there are a single morph in the CSV, so the skipped columns shouldn't be valid CSVs.
            }

            let morphs = iter
                .map(|v| {
                    v.trim()
                        .parse::<f32>()
                        .map_err(CSVParseError::MorphParseError)
                })
                .collect::<Result<Vec<_>, _>>()?;

            if fps < timestamp.frame {
                fps = timestamp.frame;
            }

            frames.push(CSVFrame { timestamp, morphs });
        }

        if frames.is_empty() {
            return Err(CSVParseError::NoFrames);
        }

        Ok(CSVAnimation {
            frames,
            morph_names,
            fps: fps + 1,
        })
    }
}

#[cfg(test)]
mod tests {
    

    use crate::{CSVAnimation, CSVParseError, Timestamp, TimestampParseError};
    #[test]
    fn given_an_empty_timestamp_it_returns_an_empty_timestamp_error() {
        let timestamp = ""
            .parse::<Timestamp>()
            .expect_err("succeeded against expectations");
        assert!(matches!(timestamp, TimestampParseError::EmptyTimestamp))
    }

    #[test]
    fn given_a_timestamp_with_more_than_4_segments_returns_a_too_many_segments_error() {
        let timestamp = "00:00:00:00:00.1234"
            .parse::<Timestamp>()
            .expect_err("succeeded against expectations");
        assert!(matches!(timestamp, TimestampParseError::TooManySegments))
    }

    #[test]
    fn given_a_zero_timestamp_it_is_parsed_correctly() {
        let timestamp = "00:00:00:00"
            .parse::<Timestamp>()
            .expect("Timestamp failed to parse");
        assert_eq!(
            timestamp,
            Timestamp {
                hour: 0,
                minute: 0,
                second: 0,
                frame: 0
            }
        )
    }

    #[test]
    fn given_a_valid_timestamp_it_is_parsed_correctly() {
        let timestamp = "01:02:03:04.123"
            .parse::<Timestamp>()
            .expect("Timestamp failed to parse");
        assert_eq!(
            timestamp,
            Timestamp {
                hour: 1,
                minute: 2,
                second: 3,
                frame: 4
            }
        )
    }

    #[test]
    fn given_no_data_it_emits_a_no_data_error() {
        assert!(matches!(
            CSVAnimation::parse("").err().unwrap(),
            CSVParseError::NoData
        ))
    }

    #[test]
    fn given_an_invalid_csv_it_emits_an_invalid_csv_error() {
        let result = CSVAnimation::parse(
            "an, invalid, csv, file
        seems to be here... right now?
        I wonder, will it be caught",
        );
        if !matches!(result, Err(CSVParseError::InvalidCSV(_))) {
            panic!("got {result:?} instead of a CSVParseError");
        }
    }

    #[test]
    fn given_a_header_row_it_sets_correct_headers() {
        let result = CSVAnimation::parse(
            "timecode, blendshapecount, shape_1, shape_2
        00:00:00:00, 0, 0, 0",
        )
        .unwrap();
        assert_eq!(result.morph_names.first().unwrap(), "shape_1");
        assert_eq!(result.morph_names.get(1).unwrap(), "shape_2");
    }

    #[test]
    fn given_no_morph_headers_it_emits_a_no_morph_error() {
        let result = CSVAnimation::parse("timecode, blendshapecount").unwrap_err();
        assert!(matches!(result, CSVParseError::NoMorphs));
    }

    #[test]
    fn given_no_frames_it_emits_a_no_frame_error() {
        let result =
            CSVAnimation::parse("timecode, blendshapecount, shape_1, shape_2").unwrap_err();
        assert!(matches!(result, CSVParseError::NoFrames));
    }

    #[test]
    fn given_a_single_frame_it_has_a_time_of_0() {
        let result = CSVAnimation::parse(
            "timecode, blendshapecount, shape_1, shape_2
00:00:00:00.00, 0, 0, 0",
        )
        .unwrap();
        assert_eq!(result.frames.first().unwrap().timestamp.frame, 0);
    }

    #[test]
    fn given_multiple_frames_can_deduce_fps() {
        let result = CSVAnimation::parse(
            "timecode, blendshapecount, shape_1, shape_2
00:00:00:00.00, 0, 0, 0
00:00:00:01.00, 0, 0, 0
00:00:00:02.00, 0, 0, 0
00:00:01:00.00, 0, 0, 0
00:00:01:01.00, 0, 0, 0",
        )
        .unwrap();
        assert_eq!(result.fps, 3);
    }

    #[test]
    fn given_a_single_frame_it_parses_morphs_correctly() {
        let result = CSVAnimation::parse(
            "timecode, blendshapecount, shape_1, shape_2
00:00:00:00.00, 0, 0.1, 0.5",
        )
        .unwrap();
        assert!(&result.frames.first().unwrap().morphs[0] - 0.1 < 0.0001);
        assert!(&result.frames.first().unwrap().morphs[1] - 0.5 < 0.0001);
    }
}