use super::*;

pub(super) fn parse_events<'a>(
    word_reader: &mut WordReader,
    vcd: &'a mut VCD,
    signal_map: &mut HashMap<String, SignalIdx>,
) -> Result<(), String> {
    loop {
        let next_word = word_reader.next_word();

        // The following is the only case where eof is not an error.
        // If we've reached the end of the file, then there is obviously
        // nothing left to do...
        if next_word.is_none() {
            break;
        };

        let (word, cursor) = next_word.unwrap();
        let Cursor(Line(_), Word(word_in_line_idx)) = cursor;
        // we only want to match on the first word in a line
        if word_in_line_idx != 1 {
            continue;
        }
        match &word[0..1] {
            "$" => {}
            "#" => {
                let value = &word[1..];
                let (f, l) = (file!(), line!());
                let value = BigUint::parse_bytes(value.as_bytes(), 10)
                    .ok_or(())
                    .map_err(|_| {
                        format!(
                            "Error near {f}:{l}. Failed to parse {value} as BigInt at {cursor:?}"
                        )
                    })?;
                let mut value = value.to_bytes_le();
                // TODO : u32 helps with less memory, but should ideally likely be
                // configurable.
                let (f, l) = (file!(), line!());
                let start_idx = u32::try_from(vcd.timeline.len()).map_err(|_| {
                    format!("Error near {f}:{l}. Failed to convert from usize to u32.")
                })?;
                vcd.timeline_markers.push(StartIdx(start_idx));
                vcd.timeline.append(&mut value);
            }

            // handle the case of an n bit signal whose value must be parsed
            "b" => {
                let binary_value = &word[1..];
                let observed_num_bits = binary_value.len();

                let mut value_u8: Vec<u8> = Vec::new();
                let mut value_string = String::new();

                let mut store_as_string = false;

                // If we encounter x or z in a value, we can recover from
                // the error and store the value as a string.
                // Or else, we we propagate up other errors.
                match binary_str_to_vec_u8(binary_value) {
                    Ok(result) => {
                        value_u8 = result;
                    }
                    Err(
                        BinaryParserErrTypes::XValue
                        | BinaryParserErrTypes::ZValue
                        | BinaryParserErrTypes::UValue,
                    ) => {
                        store_as_string = true;
                        value_string = binary_value.to_string();
                    }
                    Err(e) => {
                        let (f, l) = (file!(), line!());
                        Err(e).map_err(|e| {
                            format!("Error near {f}:{l}. Error {e:?} at {cursor:?}.")
                        })?;
                    }
                }

                // this word should be the signal alias
                let (word, cursor) = next_word!(word_reader)?;

                // lookup signal idx
                let SignalIdx(ref signal_idx) = signal_map.get(word).ok_or(()).map_err(|_| {
                    format!(
                        "Error near {}:{}. Failed to lookup signal {word} at {cursor:?}",
                        file!(),
                        line!()
                    )
                })?;

                // account for fact that signal idx could be an alias, so there
                // could be one step of indirection
                let signal_idx = {
                    let signal = vcd.all_signals.get(*signal_idx).unwrap();
                    match signal {
                        Signal::Data { .. } => *signal_idx,
                        Signal::Alias { signal_alias, .. } => {
                            let SignalIdx(ref signal_idx) = signal_alias;
                            signal_idx.clone()
                        }
                    }
                };

                // after handling potential indirection, go ahead and update the timeline
                // of the signal signal_idx references
                let signal = vcd.all_signals.get_mut(signal_idx).unwrap();
                match signal {
                    Signal::Data {
                        name,
                        sig_type,
                        ref mut signal_error,
                        num_bits,
                        u8_timeline,
                        u8_timeline_markers,
                        string_timeline,
                        string_timeline_markers,
                        ..
                    } => {
                        if signal_error.is_some() {
                            continue;
                        }

                        // Get the observed number of bits for the value parsed earlier
                        // and verify that it is not greater than the numbits declared
                        // when the signal was declared.
                        // Also account for the error case of a bitwidth of `None`
                        match num_bits {
                            Some(ref num_bits) => {
                                if observed_num_bits > *num_bits {
                                    let (f, l) = (file!(), line!());
                                    let msg = format!("\
                                        Error near {f}:{l}. The bitwidth for signal {name} \
                                        of sig_type {sig_type:?} is expected to be `{num_bits}` not \
                                        `{observed_num_bits}`. \
                                        This error occurred while parsing the vcd file at \
                                        {cursor:?}");
                                    *signal_error = Some(msg);
                                    continue;
                                }
                            }
                            None => {
                                let (f, l) = (file!(), line!());
                                let msg = format!(
                                    "\
                                    Error near {f}:{l}. The bitwidth for signal {name} \
                                    must be specified for a signal of type {sig_type:?}. \
                                    This error occurred while parsing the vcd file at \
                                    {cursor:?}"
                                );
                                Err(msg)?;
                            }
                        };

                        let (f, l) = (file!(), line!());
                        let timeline_idx = u32::try_from(vcd.timeline.len()).map_err(|_| {
                            format!("Error near {f}:{l}. Failed to convert from usize to u32.")
                        })?;
                        let timeline_idx = TimelineIdx(timeline_idx);

                        if store_as_string {
                            string_timeline_markers.push(timeline_idx);
                            string_timeline.push(value_string);
                            Ok(())
                        } else {
                            u8_timeline_markers.push(timeline_idx);

                            let mut curr_num_bytes = value_u8.len();
                            u8_timeline.append(&mut value_u8);

                            // we may need to zero extend values
                            // so that we end up storing all values
                            // of a particular signal in a consistent
                            // amount of bytes
                            let num_bits = num_bits.unwrap();
                            let bytes_required =
                                (num_bits / 8) + if (num_bits % 8) > 0 { 1 } else { 0 };

                            while curr_num_bytes < bytes_required {
                                // TODO: remove once library is known to be stable
                                // useful for debugging
                                // let err = format!("Error at {cursor:?}.\
                                // num_bits = {num_bits}, \
                                // observed_bits = {observed_num_bits}, \
                                // curr_num_bytes = {curr_num_bytes}, \
                                // bytes_required = {bytes_required} \
                                // for signal {name}");
                                // Err(err)?;

                                u8_timeline.push(0u8);
                                curr_num_bytes += 1;
                            }
                            Ok(())
                        }
                    }
                    Signal::Alias { .. } => {
                        let (f, l) = (file!(), line!());
                        let msg = format!(
                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
                                This error occurred while parsing vcd file at {cursor:?}");
                        Err(msg)
                    }
                }?;
            }

            // handle the case of a one bit signal whose value is set to `0`
            "0" => {
                // lookup signal idx
                let hash = &word[1..];
                let SignalIdx(ref signal_idx) = signal_map.get(hash).ok_or(()).map_err(|_| {
                    format!(
                        "Error near {}:{}. Failed to lookup signal {hash} at {cursor:?}",
                        file!(),
                        line!()
                    )
                })?;

                // account for fact that signal idx could be an alias, so there
                // could be one step of indirection
                let signal_idx = {
                    let signal = vcd.all_signals.get(*signal_idx).unwrap();
                    match signal {
                        Signal::Data { .. } => *signal_idx,
                        Signal::Alias { signal_alias, .. } => {
                            let SignalIdx(ref signal_idx) = signal_alias;
                            signal_idx.clone()
                        }
                    }
                };

                // after handling potential indirection, go ahead and update the timeline
                // of the signal signal_idx references
                let signal = vcd.all_signals.get_mut(signal_idx).unwrap();
                match signal {
                    Signal::Data {
                        name,
                        sig_type,
                        ref mut signal_error,
                        num_bits,
                        u8_timeline,
                        u8_timeline_markers,
                        ..
                    } => {
                        // if this is a bad signal, go ahead and skip it
                        if signal_error.is_some() {
                            continue;
                        }

                        // Get bitwidth and verify that it is 1.
                        // Also account for the error case of a bitwidth of `None`
                        match num_bits {
                            Some(ref num_bits) => {
                                if *num_bits != 1 {
                                    let (f, l) = (file!(), line!());
                                    let msg = format!(
                                        "\
                                        Error near {f}:{l}. The bitwidth for signal {name} \
                                        of sig_type {sig_type:?} is expected to be `1` not \
                                        `{num_bits}`. \
                                        This error occurred while parsing the vcd file at \
                                        {cursor:?}"
                                    );
                                    *signal_error = Some(msg);
                                    continue;
                                }
                            }
                            None => {
                                let (f, l) = (file!(), line!());
                                let msg = format!(
                                    "\
                                    Error near {f}:{l}. The bitwidth for signal {name} \
                                    must be specified for a signal of type {sig_type:?}. \
                                    This error occurred while parsing the vcd file at \
                                    {cursor:?}"
                                );
                                Err(msg)?;
                            }
                        };

                        let (f, l) = (file!(), line!());
                        let timeline_idx = u32::try_from(vcd.timeline.len()).map_err(|_| {
                            format!("Error near {f}:{l}. Failed to convert from usize to u32.")
                        })?;
                        let timeline_idx = TimelineIdx(timeline_idx);

                        u8_timeline_markers.push(timeline_idx);
                        u8_timeline.push(0u8);
                        Ok(())
                    }
                    Signal::Alias { .. } => {
                        let (f, l) = (file!(), line!());
                        let msg = format!(
                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
                             This error occurred while parsing vcd file at {cursor:?}");
                        Err(msg)
                    }
                }?;
            }

            "1" => {
                // lokup signal idx
                let hash = &word[1..];
                let SignalIdx(ref signal_idx) = signal_map.get(hash).ok_or(()).map_err(|_| {
                    format!(
                        "Error near {}:{}. Failed to lookup signal {hash} at {cursor:?}",
                        file!(),
                        line!()
                    )
                })?;

                // account for fact that signal idx could be an alias, so there
                // could be one step of indirection
                let signal_idx = {
                    let signal = vcd.all_signals.get(*signal_idx).unwrap();
                    match signal {
                        Signal::Data { .. } => *signal_idx,
                        Signal::Alias { signal_alias, .. } => {
                            let SignalIdx(ref signal_idx) = signal_alias;
                            signal_idx.clone()
                        }
                    }
                };

                // after handling potential indirection, go ahead and update the timeline
                // of the signal signal_idx references
                let signal = vcd.all_signals.get_mut(signal_idx).unwrap();
                match signal {
                    Signal::Data {
                        name,
                        sig_type,
                        ref mut signal_error,
                        num_bits,
                        u8_timeline,
                        u8_timeline_markers,
                        ..
                    } => {
                        // if this is a bad signal, go ahead and skip it
                        if signal_error.is_some() {
                            continue;
                        }

                        // Get bitwidth and verify that it is 1.
                        // Also account for the error case of a bitwidth of `None`
                        match num_bits {
                            Some(ref num_bits) => {
                                if *num_bits != 1 {
                                    let (f, l) = (file!(), line!());
                                    let msg = format!(
                                        "\
                                        Error near {f}:{l}. The bitwidth for signal {name} \
                                        of sig_type {sig_type:?} is expected to be `1` not \
                                        `{num_bits}`. \
                                        This error occurred while parsing the vcd file at \
                                        {cursor:?}"
                                    );
                                    *signal_error = Some(msg);
                                    continue;
                                }
                            }
                            None => {
                                let (f, l) = (file!(), line!());
                                let msg = format!(
                                    "\
                                    Error near {f}:{l}. The bitwidth for signal {name} \
                                    must be specified for a signal of type {sig_type:?}. \
                                    This error occurred while parsing the vcd file at \
                                    {cursor:?}"
                                );
                                Err(msg)?;
                            }
                        };

                        let (f, l) = (file!(), line!());
                        let timeline_idx = u32::try_from(vcd.timeline.len()).map_err(|_| {
                            format!("Error near {f}:{l}. Failed to convert from usize to u32.")
                        })?;
                        let timeline_idx = TimelineIdx(timeline_idx);

                        u8_timeline_markers.push(timeline_idx);
                        u8_timeline.push(1u8);
                        Ok(())
                    }
                    Signal::Alias { .. } => {
                        let (f, l) = (file!(), line!());
                        let msg = format!(
                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
                             This error occurred while parsing vcd file at {cursor:?}");
                        Err(msg)
                    }
                }?;
            }
            // other one bit cases
            "x" | "X" | "z" | "Z" | "u" | "U" => {
                let val = word.to_string();
                // lokup signal idx
                let hash = &word[1..];
                let SignalIdx(ref signal_idx) = signal_map.get(hash).ok_or(()).map_err(|_| {
                    format!(
                        "Error near {}:{}. Failed to lookup signal {hash} at {cursor:?}",
                        file!(),
                        line!()
                    )
                })?;

                // account for fact that signal idx could be an alias, so there
                // could be one step of indirection
                let signal_idx = {
                    let signal = vcd.all_signals.get(*signal_idx).unwrap();
                    match signal {
                        Signal::Data { .. } => *signal_idx,
                        Signal::Alias { signal_alias, .. } => {
                            let SignalIdx(ref signal_idx) = signal_alias;
                            signal_idx.clone()
                        }
                    }
                };

                // after handling potential indirection, go ahead and update the timeline
                // of the signal signal_idx references
                let signal = vcd.all_signals.get_mut(signal_idx).unwrap();
                match signal {
                    Signal::Data {
                        name,
                        sig_type,
                        ref mut signal_error,
                        num_bits,
                        string_timeline,
                        string_timeline_markers,
                        ..
                    } => {
                        // if this is a bad signal, go ahead and skip it
                        if signal_error.is_some() {
                            continue;
                        }

                        // Get bitwidth and verify that it is 1.
                        // Also account for the error case of a bitwidth of `None`
                        match num_bits {
                            Some(ref num_bits) => {
                                if *num_bits != 1 {
                                    let (f, l) = (file!(), line!());
                                    let msg = format!(
                                        "\
                                        Error near {f}:{l}. The bitwidth for signal {name} \
                                        of sig_type {sig_type:?} is expected to be `1` not \
                                        `{num_bits}`. \
                                        This error occurred while parsing the vcd file at \
                                        {cursor:?}"
                                    );
                                    *signal_error = Some(msg);
                                    continue;
                                }
                            }
                            None => {
                                let (f, l) = (file!(), line!());
                                let msg = format!(
                                    "\
                                    Error near {f}:{l}. The bitwidth for signal {name} \
                                    must be specified for a signal of type {sig_type:?}. \
                                    This error occurred while parsing the vcd file at \
                                    {cursor:?}"
                                );
                                Err(msg)?;
                            }
                        };

                        let (f, l) = (file!(), line!());
                        let timeline_idx = u32::try_from(vcd.timeline.len()).map_err(|_| {
                            format!("Error near {f}:{l}. Failed to convert from usize to u32.")
                        })?;
                        let timeline_idx = TimelineIdx(timeline_idx);

                        string_timeline_markers.push(timeline_idx);
                        string_timeline.push(val);
                        Ok(())
                    }
                    Signal::Alias { .. } => {
                        let (f, l) = (file!(), line!());
                        let msg = format!(
                            "Error near {f}:{l}, a signal alias should not point to a signal alias.\n\
                             This error occurred while parsing vcd file at {cursor:?}");
                        Err(msg)
                    }
                }?;
            }

            _ => {}
        }
    }

    Ok(())
}