// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.

//! This mod provides functions to remap a `JsError` based on a source map.

use deno_core::error::JsError;
use sourcemap::SourceMap;
use std::collections::HashMap;
use std::str;

pub trait SourceMapGetter: Sync + Send + Clone {
  /// Returns the raw source map file.
  fn get_source_map(&self, file_name: &str) -> Option<Vec<u8>>;
  fn get_source_line(
    &self,
    file_name: &str,
    line_number: usize,
  ) -> Option<String>;
}

/// Cached filename lookups. The key can be None if a previous lookup failed to
/// find a SourceMap.
pub type CachedMaps = HashMap<String, Option<SourceMap>>;

/// Apply a source map to a `deno_core::JsError`, returning a `JsError` where
/// file names and line/column numbers point to the location in the original
/// source, rather than the transpiled source code.
pub fn apply_source_map<G: SourceMapGetter>(
  js_error: &JsError,
  getter: G,
) -> JsError {
  // Note that js_error.frames has already been source mapped in
  // prepareStackTrace().
  let mut mappings_map: CachedMaps = HashMap::new();

  let (script_resource_name, line_number, start_column, source_line) =
    get_maybe_orig_position(
      js_error.script_resource_name.clone(),
      js_error.line_number,
      // start_column is 0-based, we need 1-based here.
      js_error.start_column.map(|n| n + 1),
      &mut mappings_map,
      getter.clone(),
    );
  let start_column = start_column.map(|n| n - 1);
  // It is better to just move end_column to be the same distance away from
  // start column because sometimes the code point is not available in the
  // source file map.
  let end_column = match js_error.end_column {
    Some(ec) => {
      start_column.map(|sc| ec - (js_error.start_column.unwrap() - sc))
    }
    _ => None,
  };

  let mut script_resource_name = script_resource_name;
  let mut line_number = line_number;
  let mut start_column = start_column;
  let mut end_column = end_column;
  let mut source_line = source_line;
  if script_resource_name
    .as_ref()
    .map_or(true, |s| s.starts_with("deno:"))
  {
    for frame in &js_error.frames {
      if let (Some(file_name), Some(line_number_)) =
        (&frame.file_name, frame.line_number)
      {
        if !file_name.starts_with("deno:") {
          script_resource_name = Some(file_name.clone());
          line_number = Some(line_number_);
          start_column = frame.column_number.map(|n| n - 1);
          end_column = frame.column_number;
          // Lookup expects 0-based line and column numbers, but ours are 1-based.
          source_line =
            getter.get_source_line(file_name, (line_number_ - 1) as usize);
          break;
        }
      }
    }
  }

  JsError {
    message: js_error.message.clone(),
    source_line,
    script_resource_name,
    line_number,
    start_column,
    end_column,
    frames: js_error.frames.clone(),
    stack: None,
  }
}

fn get_maybe_orig_position<G: SourceMapGetter>(
  file_name: Option<String>,
  line_number: Option<i64>,
  column_number: Option<i64>,
  mappings_map: &mut CachedMaps,
  getter: G,
) -> (Option<String>, Option<i64>, Option<i64>, Option<String>) {
  match (file_name, line_number, column_number) {
    (Some(file_name_v), Some(line_v), Some(column_v)) => {
      let (file_name, line_number, column_number, source_line) =
        get_orig_position(file_name_v, line_v, column_v, mappings_map, getter);
      (
        Some(file_name),
        Some(line_number),
        Some(column_number),
        source_line,
      )
    }
    _ => (None, None, None, None),
  }
}

pub fn get_orig_position<G: SourceMapGetter>(
  file_name: String,
  line_number: i64,
  column_number: i64,
  mappings_map: &mut CachedMaps,
  getter: G,
) -> (String, i64, i64, Option<String>) {
  // Lookup expects 0-based line and column numbers, but ours are 1-based.
  let line_number = line_number - 1;
  let column_number = column_number - 1;

  let default_pos = (file_name.clone(), line_number, column_number, None);
  let maybe_source_map = get_mappings(&file_name, mappings_map, getter.clone());
  let (file_name, line_number, column_number, source_line) =
    match maybe_source_map {
      None => default_pos,
      Some(source_map) => {
        match source_map.lookup_token(line_number as u32, column_number as u32)
        {
          None => default_pos,
          Some(token) => match token.get_source() {
            None => default_pos,
            Some(source_file_name) => {
              // The `source_file_name` written by tsc in the source map is
              // sometimes only the basename of the URL, or has unwanted `<`/`>`
              // around it. Use the `file_name` we get from V8 if
              // `source_file_name` does not parse as a URL.
              let file_name = match deno_core::resolve_url(source_file_name) {
                Ok(m) if m.scheme() == "blob" => file_name,
                Ok(m) => m.to_string(),
                Err(_) => file_name,
              };
              let source_line =
                if let Some(source_view) = token.get_source_view() {
                  source_view
                    .get_line(token.get_src_line())
                    .map(|s| s.to_string())
                } else {
                  None
                };
              (
                file_name,
                i64::from(token.get_src_line()),
                i64::from(token.get_src_col()),
                source_line,
              )
            }
          },
        }
      }
    };
  let source_line = source_line
    .or_else(|| getter.get_source_line(&file_name, line_number as usize));
  (file_name, line_number + 1, column_number + 1, source_line)
}

fn get_mappings<'a, G: SourceMapGetter>(
  file_name: &str,
  mappings_map: &'a mut CachedMaps,
  getter: G,
) -> &'a Option<SourceMap> {
  mappings_map
    .entry(file_name.to_string())
    .or_insert_with(|| parse_map_string(file_name, getter))
}

// TODO(kitsonk) parsed source maps should probably be cached in state in
// the module meta data.
fn parse_map_string<G: SourceMapGetter>(
  file_name: &str,
  getter: G,
) -> Option<SourceMap> {
  getter
    .get_source_map(file_name)
    .and_then(|raw_source_map| SourceMap::from_slice(&raw_source_map).ok())
}

#[cfg(test)]
mod tests {
  use super::*;

  #[derive(Clone)]
  struct MockSourceMapGetter {}

  impl SourceMapGetter for MockSourceMapGetter {
    fn get_source_map(&self, file_name: &str) -> Option<Vec<u8>> {
      let s = match file_name {
        "foo_bar.ts" => {
          r#"{"sources": ["foo_bar.ts"], "mappings":";;;IAIA,OAAO,CAAC,GAAG,CAAC,qBAAqB,EAAE,EAAE,CAAC,OAAO,CAAC,CAAC;IAC/C,OAAO,CAAC,GAAG,CAAC,eAAe,EAAE,IAAI,CAAC,QAAQ,CAAC,IAAI,CAAC,CAAC;IACjD,OAAO,CAAC,GAAG,CAAC,WAAW,EAAE,IAAI,CAAC,QAAQ,CAAC,EAAE,CAAC,CAAC;IAE3C,OAAO,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC"}"#
        }
        "bar_baz.ts" => {
          r#"{"sources": ["bar_baz.ts"], "mappings":";;;IAEA,CAAC,KAAK,IAAI,EAAE;QACV,MAAM,GAAG,GAAG,sDAAa,OAAO,2BAAC,CAAC;QAClC,OAAO,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;IACnB,CAAC,CAAC,EAAE,CAAC;IAEQ,QAAA,GAAG,GAAG,KAAK,CAAC;IAEzB,OAAO,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC"}"#
        }
        _ => return None,
      };
      Some(s.as_bytes().to_owned())
    }

    fn get_source_line(
      &self,
      file_name: &str,
      line_number: usize,
    ) -> Option<String> {
      let s = match file_name {
        "foo_bar.ts" => vec![
          "console.log('foo');",
          "console.log('foo');",
          "console.log('foo');",
          "console.log('foo');",
          "console.log('foo');",
        ],
        _ => return None,
      };
      if s.len() > line_number {
        Some(s[line_number].to_string())
      } else {
        None
      }
    }
  }

  #[test]
  fn apply_source_map_line() {
    let e = JsError {
      message: "TypeError: baz".to_string(),
      source_line: Some("foo".to_string()),
      script_resource_name: Some("foo_bar.ts".to_string()),
      line_number: Some(4),
      start_column: Some(16),
      end_column: None,
      frames: vec![],
      stack: None,
    };
    let getter = MockSourceMapGetter {};
    let actual = apply_source_map(&e, getter);
    assert_eq!(actual.source_line, Some("console.log('foo');".to_string()));
  }
}