use chrono::Local;
use colored::Colorize;
use env_logger::Env;
use log::{Level, Record};
use std::fmt;
use std::io::Write;
use std::str::FromStr;

/// SDK Log Level Enum
#[derive(Clone, Copy, Debug)]
pub enum SDKLogLevel {
    /// A critical error.
    /// Maps to "Error" in log crate.
    Critical = 1,
    /// A standard error.
    /// Maps to "Warn" in log crate.
    Error,
    /// A warning.
    /// Maps to "Info" in log crate.
    Warning,
    /// An informative message.
    /// Logs to "Debug" in log crate.
    Info,
    /// A debug message.
    /// Maps to "Trace" in log crate.
    Debug,
}

// String equivalent of above enum.
// Extra string added at start of string to help translation from enum to string processes.
static SDK_LOG_LEVEL_NAMES: [&str; 6] = ["None", "Critical", "Error", "Warning", "Info", "Debug"];
static SDK_LOG_LEVEL_INT_STRS: [&str; 6] = ["0", "1", "2", "3", "4", "5"];
// The logging environment variable used to overwrite the logging levels.
static LOG_ENV_VAR: &str = "CELP_LOG";
// Default logging level
static DEFAULT_LOG_LEVEL: SDKLogLevel = SDKLogLevel::Info;
// Log level parsing error message
static LEVEL_PARSE_ERROR: &str =
    "attempted to convert a string that doesn't match an existing SDK log level";

/// The type returned by [`from_str`] when the string doesn't match any of the log levels.
///
/// [`from_str`]: https://doc.rust-lang.org/std/str/trait.FromStr.html#tymethod.from_str
#[allow(missing_copy_implementations)]
#[derive(Debug, PartialEq, Eq)]
pub struct ParseSDKLevelError(());

impl fmt::Display for ParseSDKLevelError {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.write_str(LEVEL_PARSE_ERROR)
    }
}

// The Error trait is not available in libcore
#[cfg(feature = "std")]
impl error::Error for ParseLevelError {}

fn ok_or<T, E>(t: Option<T>, e: E) -> Result<T, E> {
    match t {
        Some(t) => Ok(t),
        None => Err(e),
    }
}

impl FromStr for SDKLogLevel {
    type Err = ParseSDKLevelError;
    /// Retrieve the SDK log value from a string value that is the integer value of the SDK log level.
    /// For example, "3" would return SDKLogLevel::Warning.
    fn from_str(level: &str) -> Result<SDKLogLevel, Self::Err> {
        ok_or(
            SDK_LOG_LEVEL_INT_STRS
                .iter()
                .position(|&name| name.eq_ignore_ascii_case(level))
                .into_iter()
                .filter(|&idx| idx != 0)
                .map(|idx| SDKLogLevel::from_usize(idx).unwrap())
                .next(),
            ParseSDKLevelError(()),
        )
    }
}

// Implementation used to convert SDKLogLevel enums to strings.
impl fmt::Display for SDKLogLevel {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        fmt.pad(self.as_str())
    }
}

/// SDKLogLevel implementation
impl SDKLogLevel {
    /// Returns max logging level available.
    pub fn max() -> SDKLogLevel {
        SDKLogLevel::Debug
    }

    /// Returns min logging level available.
    pub fn min() -> SDKLogLevel {
        SDKLogLevel::Critical
    }

    /// Returns the converted string value of the SDKLogLevel enum.
    pub fn as_str(&self) -> &'static str {
        SDK_LOG_LEVEL_NAMES[*self as usize]
    }

    pub fn from_usize(u: usize) -> Option<SDKLogLevel> {
        match u {
            1 => Some(SDKLogLevel::Critical),
            2 => Some(SDKLogLevel::Error),
            3 => Some(SDKLogLevel::Warning),
            4 => Some(SDKLogLevel::Info),
            5 => Some(SDKLogLevel::Debug),
            _ => None,
        }
    }
}

/// Implement 'From' and 'Into' functionality to convert the Log levels we like to the levels that the crate uses.
/// This means we can do something like: 'let log_level: Level = SDKLogLevel::Info.into();'
impl From<SDKLogLevel> for Level {
    fn from(sdk_ll: SDKLogLevel) -> Self {
        match sdk_ll {
            SDKLogLevel::Critical => Level::Error,
            SDKLogLevel::Error => Level::Warn,
            SDKLogLevel::Warning => Level::Info,
            SDKLogLevel::Info => Level::Debug,
            SDKLogLevel::Debug => Level::Trace,
        }
    }
}

/// Same as above, but the other way around.
impl From<Level> for SDKLogLevel {
    fn from(sdk_ll: Level) -> Self {
        match sdk_ll {
            Level::Error => SDKLogLevel::Critical,
            Level::Warn => SDKLogLevel::Error,
            Level::Info => SDKLogLevel::Warning,
            Level::Debug => SDKLogLevel::Info,
            Level::Trace => SDKLogLevel::Debug,
        }
    }
}

/// Initialise the logging functionality to a certain level.
///
/// # Arguments
///
/// * `module_name` - A string to denote the calling application. It can be any string. It does not have to match the exact application name.
/// * `log_level` - The level of logging to use. If not given, will use default logging level.
pub fn init_logger(module_name: &str, log_level: Option<SDKLogLevel>) {
    // Set default logging level (converts to "Info" for our logging levels).
    let mut converted_log_level: Level = DEFAULT_LOG_LEVEL.into();
    // Convert the SDKLogLevel to standard Level type
    // If a log level was specified.
    if let Some(ll) = log_level {
        // Convert the SDKLogLevel to Level.
        converted_log_level = ll.into();
    }

    // Set up a new Builder instance here so that we can ignore some of the presets like the "RUST_LOG" environment variable and such.
    let mut builder = env_logger::Builder::new();

    // Convert the 'Level' type to 'LevelFilter' type with 'to_level_filter'.
    // NOTE: After some testing, it is seen that `filter_level` is required first before setting `filter_module` or else the level filter does not get set correctly.
    builder.filter_level(converted_log_level.to_level_filter());
    // Then set the filter for the module.
    builder.filter_module(module_name, converted_log_level.to_level_filter());

    // Need to check if the custom environment variable is set first.
    if std::env::var(LOG_ENV_VAR).is_ok() {
        // Specify a custom environment variable other than the default "RUST_LOG"
        let env = Env::new().filter(LOG_ENV_VAR);
        // Set the environment variable to use for overwriting log levels.
        builder.parse_env(env);
    }
    // Set the output as stdout (env_logger uses stderr by default).
    builder.target(env_logger::Target::Stdout);

    //Format the output message.
    builder.format(|buf, record| writeln!(buf, "{}", format_log_str(record)));

    // Initialise the builder.
    builder.init();
}

/// Format the log string in a similar manner to C++ SDK logger.
/// Will output in the following format:
/// "[12:34:56 +02:00] [main.rs:123] [---D---] log message"
fn format_log_str(record: &Record) -> String {
    // Get the current time.
    let now = Local::now();
    let formatted_time = now.format("[%H:%M:%S%.6f %:z]").to_string();
    // Get the file name or use the default string.
    let filename = record.file().unwrap_or("Unknown file path");
    let line = record.line().unwrap_or(0);
    // Convert the log level to a str, iterator over the characters and grab the first letter.
    let sdk_log_level: SDKLogLevel = record.level().into();
    let short_log_level_char = sdk_log_level.as_str().chars().next().unwrap();
    let mut short_log_level_str = String::from("---X---");
    // Replace the "X" with the correct character.
    short_log_level_str.replace_range(3..4, &short_log_level_char.to_string());
    // Based on the log level, the string should be a different colour.
    // TODO: Confirm color choice with C++ version.
    let short_log_level_str_colored = match sdk_log_level {
        SDKLogLevel::Critical => short_log_level_str.purple(),
        SDKLogLevel::Error => short_log_level_str.red(),
        SDKLogLevel::Warning => short_log_level_str.yellow(),
        SDKLogLevel::Info => short_log_level_str.green(),
        SDKLogLevel::Debug => short_log_level_str.blue(),
    };

    // NOTE: Will not implement thread ID printing for now. Rust doesn't have any nice ways for this library to get the thread ID of the calling application.
    //       We would have to pss the thread ID directly from the calling application. That would just be messy.
    format!(
        "{} [{:?}:{:?}] [{}] {:?}",
        formatted_time,
        filename,
        line,
        short_log_level_str_colored,
        record.args()
    )
}

/// The following macros convert the 'log' crates macros to use our own log levels.
/// ___________________
/// | SDK      | log   |
/// |__________|_______|
/// | critical | error |
/// | error    | warn  |
/// | warning  | info  |
/// | info     | debug |
/// | debug    | trace |
#[macro_export]
macro_rules! critical {
    ($($arg:tt)*) => {
        // Delegate to the 'log' crates 'error!' macro
        log::error!($($arg)*);
    }
}

#[macro_export]
macro_rules! error {
    ($($arg:tt)*) => {
        // Delegate to the 'log' crates 'warn!' macro
        log::warn!($($arg)*);
    }
}

#[macro_export]
macro_rules! warning {
    ($($arg:tt)*) => {
        // Delegate to the 'log' crates 'info!' macro
        log::info!($($arg)*);
    }
}

#[macro_export]
macro_rules! info {
    ($($arg:tt)*) => {
        // Delegate to the 'log' crates 'debug!' macro
        log::debug!($($arg)*);
    }
}

#[macro_export]
macro_rules! debug {
    ($($arg:tt)*) => {
        // Delegate to the 'log' crates 'error!' macro
        log::trace!($($arg)*);
    }
}