//! Switches between [Visual Studio Code](https://code.visualstudio.com/) themes
//!
//! ## Usage: Windows & macOS
//! Since [version
//! 1.42](https://code.visualstudio.com/updates/v1_42#_auto-switch-theme-based-on-os-color-scheme),
//! Visual Studio Code can listen to Windows and macOS color scheme changes and switch to a
//! matching theme.  It's recommended for use on those platforms.
//!
//! ## Usage: Linux & BSD
//! Visual Studio Code doesn't support OS synchronization on Linux and non-Apple BSDs, so `thcon`
//! is the recommended method.  Visual Studio Code monitors its `settings.json` file for changes
//! while it's running.  Because that `settings.json` file can include comments, the simplest way
//! to preserve existing whitespace and comments is by looking for a magic comment annotating the
//! `workbench.colorTheme` setting.
//!
//! In your `settings.json`, mark the `workspace.colorTheme` line so `thcon` can find it:
//!
//! ```jsonc
//! {
//!   // ... other settings
//!
//!   "workbench.colorTheme": "" // thcon:replace-line
//! }
//! ```
//!
//! In your `thcon.toml`, define light and dark themes:
//!
//! ```toml
//! [vscode]
//! dark = "Solarized Dark"
//! light = "Solarized Light"
//!
//! # optionally, tell thcon where your settings.json is stored
//! config = "/path/to/settings.json"
//! ```
//!
//! ## `thcon.toml` Schema
//! Section: `vscode`
//!
//! | Key | Type | Description | Default |
//! | --- | ---- | ----------- | -------- |
//! | `disabled` | boolean | `true` to disable theming of this app, otherwise `false` | `false` |
//! | `dark` | string | The theme to use in dark mode | Default Dark+ |
//! | `light` | string | The theme to use in light mode | Default Light+ |
//! | `config` | string | Absolute path to your `settings.json` file | `~/.config/Code/User/settings.json` |

use std::path::PathBuf;
use std::{fs, io};

use anyhow::{Context, Result};
use log::debug;
use regex::{Captures, Regex};
use serde::Deserialize;

use crate::config::Config as ThconConfig;
use crate::operation::Operation;
use crate::themeable::{ConfigState, Themeable};
use crate::AppConfig;
use crate::Disableable;

#[derive(Debug, Deserialize, Disableable, AppConfig)]
pub struct _Config {
    light: String,
    dark: String,
    config: Option<String>,
    #[serde(default)]
    disabled: bool,
}

impl Default for _Config {
    fn default() -> Self {
        Self {
            light: "Default Light+".to_string(),
            dark: "Default Dark+".to_string(),
            config: None,
            disabled: false,
        }
    }
}

pub struct VSCode;

impl VSCode {
    fn settings_json_path(&self) -> PathBuf {
        [
            dirs::config_dir().unwrap().to_str().unwrap(),
            "Code",
            "User",
            "settings.json",
        ]
        .iter()
        .collect()
    }
}

impl Themeable for VSCode {
    fn config_state(&self, config: &ThconConfig) -> ConfigState {
        ConfigState::with_default_config(config.vscode.as_ref().map(|c| c.inner.as_ref()))
    }

    fn switch(&self, config: &ThconConfig, operation: &Operation) -> Result<()> {
        let default_config = _Config::default();

        let config = match self.config_state(config) {
            ConfigState::NoDefault => unreachable!(),
            ConfigState::Disabled => return Ok(()),
            ConfigState::Default => &default_config,
            ConfigState::Enabled => config.vscode.as_ref().unwrap().unwrap_inner_left(),
        };

        let theme = match operation {
            Operation::Darken => &config.dark,
            Operation::Lighten => &config.light,
        };

        let settings_path = self.settings_json_path();
        debug!(
            "Reading/writing settings.json at {}",
            &settings_path.display()
        );
        match fs::read_to_string(self.settings_json_path()) {
            Ok(settings) => {
                let settings = replace_color_theme(&settings, theme);
                fs::write(self.settings_json_path(), settings).with_context(|| {
                    format!("Unable to write settings to {}", &settings_path.display())
                })
            }
            Err(e) => {
                if e.kind() == io::ErrorKind::NotFound {
                    // allow settings.json to not exist at all
                    Ok(())
                } else {
                    Err(anyhow::Error::new(e).context(format!(
                        "Unable to read settings from {}",
                        &settings_path.display()
                    )))
                }
            }
        }
    }
}

fn replace_color_theme(settings_json: &str, new_theme: &str) -> String {
    let theme_regex = Regex::new(
        r#"^(?P<prefix>\s*"workbench.colorTheme"\s*:\s*)"(?P<v>.+)"(?P<suffix>,?\s*//\s*thcon:replace-line)"#,
    );
    match theme_regex {
        Err(_) => settings_json.to_owned(),
        Ok(theme_regex) => {
            let modified_lines: Vec<String> = settings_json
                .lines()
                .map(|line| {
                    theme_regex
                        .replace(line, |caps: &Captures| {
                            format!(r#"{}"{}"{}"#, &caps["prefix"], new_theme, &caps["suffix"])
                        })
                        .into_owned()
                })
                .collect();

            modified_lines.join("\n")
        }
    }
}

#[test]
fn replace_color_trailing_comma() {
    let settings_json = r#"
    {
        "workbench.colorTheme": "Default Dark+", // thcon:replace-line
        "editor.minimap.enabled": false,
    }
    "#;
    let res = replace_color_theme(settings_json, "Default Light+");
    assert_eq!(
        res,
        r#"
    {
        "workbench.colorTheme": "Default Light+", // thcon:replace-line
        "editor.minimap.enabled": false,
    }
    "#
    );
}

#[test]
fn replace_color_no_trailing_comma() {
    let settings_json = r#"
    {
        "editor.minimap.enabled": false,
        "workbench.colorTheme"  :"Default Dark+"   // thcon:replace-line
    }
    "#;
    let res = replace_color_theme(settings_json, "Default Light+");
    assert_eq!(
        res,
        r#"
    {
        "editor.minimap.enabled": false,
        "workbench.colorTheme"  :"Default Light+"   // thcon:replace-line
    }
    "#
    );
}