use crate::is_dry_run;
use crate::key_value::KeyValueStore as KV;
use std::error::Error;
use std::io::{self, Write};

/// Text shown for an empty field.
const EMPTY_VALUE: &str = "(empty)";
/// Text shown in place of a password.
const HIDDEN_PASSWORD: &str = "*****";

// highlight some of the info
const ANSI_GROUP: &str = "\x1b[1;31m";
const ANSI_FIELD: &str = "\x1b[1;33m";
const ANSI_NOTICE: &str = "\x1b[33m";
const ANSI_RESET: &str = "\x1b[0m";

/* ***** config structure definition ***** */

/// Describes a field in the configuration.
pub enum CfgField<'a> {
    /// Silently writes a default to the DB if absent, never prompts for changes.
    Silent { key: &'a str, default: &'a str },
    /// Writes a default, asks for changes.
    Default { key: &'a str, default: &'a str, description: &'a str },
    /// No default, asks for value, but can stay empty.
    Optional { key: &'a str, description: &'a str },
    /// Empty by default, required, will prompt without echo.
    Password { key: &'a str, description: &'a str },
    /// Empty by default, can be user-provided, or will be generated randomly.
    RandomId {
        key: &'a str,
        generator: fn(config: &KV, is_dry_run: bool) -> Result<String, Box<dyn Error>>,
        generator_description: &'a str,
        description: &'a str,
    },
}

/// A group of related config fields. The final key of an inner value will be
/// `{group.name}-{key}`.
pub struct CfgGroup<'a> {
    pub name: &'a str,
    pub description: &'a str,
    pub fields: &'a [CfgField<'a>],
}

/// A description of the entire config, as a collection of named groups.
///
/// Used both to populate defaults and to interactively adjust the configuration.
pub struct CfgSpec<'a> {
    pub groups: &'a [CfgGroup<'a>],
}

impl<'a> CfgField<'a> {
    /// Silent fields don't get prompted or shown.
    fn is_silent(&self) -> bool {
        matches!(self, CfgField::Silent { .. })
    }

    /// Password fields will be censored when displayed.
    fn is_password(&self) -> bool {
        matches!(self, CfgField::Password { .. })
    }

    /// Optional fields are allowed to be (and stay) empty.
    fn is_optional(&self) -> bool {
        matches!(self, CfgField::Optional { .. })
    }

    /// Reports if the field needs changing or is ok as-is.
    ///
    /// (Because of the default population at boot, Silent and Default must
    /// *necessarily* always have a value. Optional is optional.  Only
    /// Password and RandomId might need actions if they are missing.)
    fn is_action_required(&self, config: &KV, grpname: &str) -> bool {
        if matches!(
            self,
            CfgField::Silent { .. } | CfgField::Default { .. } | CfgField::Optional { .. }
        ) {
            false
        } else {
            config.get(self.full_key(grpname).as_str()).ok().is_none()
        }
    }

    /// Gets `key`, which is the local part of the field name. (`.full_key` is used for the DB.)
    fn key(&self) -> String {
        match self {
            CfgField::Silent { key, .. } => key,
            CfgField::Default { key, .. } => key,
            CfgField::Optional { key, .. } => key,
            CfgField::Password { key, .. } => key,
            CfgField::RandomId { key, .. } => key,
        }
        .to_string()
    }

    /// Full field name / key used in the DB (currently `{grpname}-{fieldname}`.)
    fn full_key(&self, grpname: &str) -> String {
        format!("{}-{}", grpname, self.key())
    }

    /// Gets `description` or "(none)".
    fn description(&self) -> String {
        match self {
            CfgField::Silent { .. } => "(none)",
            CfgField::Default { description, .. } => description,
            CfgField::Optional { description, .. } => description,
            CfgField::Password { description, .. } => description,
            CfgField::RandomId { description, .. } => description,
        }
        .to_string()
    }

    /// Gets a description of the default value if one exists.  
    /// (Either the value itself, or a description of the generator making a default value.)
    fn default_description(&self) -> Option<String> {
        match self {
            CfgField::Silent { default, .. } => Some(default.to_string()),
            CfgField::Default { default, .. } => Some(default.to_string()),
            CfgField::RandomId { generator_description, .. } => {
                Some(format!("{}{}{}", '(', generator_description, ')'))
            },
            _ => None,
        }
    }

    /// Gets the actual default value, which may involve running a generator.
    fn default_value(&self, config: &KV) -> Result<Option<String>, Box<dyn Error>> {
        match self {
            CfgField::Silent { default, .. } => Ok(Some(default.to_string())),
            CfgField::Default { default, .. } => Ok(Some(default.to_string())),
            CfgField::RandomId { generator, .. } => generator(config, is_dry_run()).map(Some),
            _ => Ok(None),
        }
    }
}

/// Ensure all fields with known default values exist.
pub fn populate_defaults(spec: &CfgSpec, config: &KV) {
    for group in spec.groups {
        for field in group.fields {
            match field {
                CfgField::Silent { default, .. } => {
                    config.default(&field.full_key(group.name), default)
                },
                CfgField::Default { default, .. } => {
                    config.default(&field.full_key(group.name), default)
                },
                _ => {},
            }
        }
    }
}

/// Check all groups / fields and interactively edit as needed.
///
/// Will report if the config is fine or has missing values.
pub fn interactive_check(spec: &CfgSpec, config: KV) -> Result<(), Box<dyn Error>> {
    let mut all_valid: bool = true;
    for group in spec.groups {
        group_header(group.name, group.description);
        let todo = needs_info(&config, group);
        // TODO: add distinction between edit all / edit necessary only
        let choices = if !todo.is_empty() {
            println!(
                "{}The following fields need adjustment: {}{}",
                ANSI_NOTICE,
                todo.join(", "),
                ANSI_RESET
            );
            &["[E]dit (default)", "[L]ist all", "[S]kip group"]
        } else {
            println!(
                "{}This group looks fine. OK to [S]kip, unless you want to adjust values here.{}",
                ANSI_NOTICE, ANSI_RESET
            );
            &["[S]kip group (default)", "[E]dit", "[L]ist all"]
        };
        loop {
            let choice = prompt_action(choices);
            match choice {
                'L' => {
                    show_group(&config, group);
                },
                'E' => {
                    for field in group.fields {
                        check_field(&config, group.name, field, &mut all_valid)?;
                    }
                    break;
                },
                'S' => {
                    if !todo.is_empty() {
                        all_valid = false;
                    }
                    break;
                },
                _ => {
                    unreachable!();
                }, // (prompt already checks)
            }
        }
    }
    if all_valid {
        Ok(())
    } else {
        Err("WARNING: Config is incomplete. Re-run to fix.".into())
    }
}

fn check_field(
    config: &KV, grpname: &str, field: &CfgField, ok: &mut bool,
) -> Result<(), Box<dyn Error>> {
    if field.is_silent() {
        return Ok(());
    }
    show_field(config, grpname, field);
    let key = field.full_key(grpname);
    let value = config.get(&key).ok();
    let mut actions: Vec<&'static str> = Vec::new();
    // TODO: adjust order: empty password should offer input first
    // TODO: RandomId should offer generating as [R]egenerate
    if value.is_some() | field.is_password() | field.is_optional() {
        actions.push("[K]eep as-is");
    }
    if field.default_description().is_some() {
        actions.push("[R]eset to default");
    }
    if field.is_password() {
        actions.push("[R]emove");
    }
    actions.push("[I]nput new value");
    if !field.is_password() {
        actions.push("[L]ong (multiline) input")
    };

    match prompt_action(&actions) {
        'K' => {
            // we allow leaving a password empty, but that means config is incomplete
            if value.is_none() & !field.is_optional() {
                *ok &= false;
            }
        },
        'R' => {
            match field.default_value(&config)? {
                Some(value) => {
                    config.set(&key, &value)?;
                },
                // password again
                None => {
                    config.delete(&key)?;
                    *ok &= false;
                },
            }
        },
        'I' => {
            let value = if field.is_password() { prompt_password() } else { prompt_single_line() };
            config.set(&key, &value)?;
        },
        'L' => {
            let value = prompt_multiline();
            config.set(&key, &value)?;
        },
        _ => {
            return Err("Wat.".into());
        },
    }
    Ok(())
}

/* ***** displaying various kinds of info ***** */

fn group_header(name: &str, description: &str) {
    println!("==============================");
    println!("{}{}{} - {}", ANSI_GROUP, name, ANSI_RESET, description);
    println!("");
}

fn show_group(config: &KV, group: &CfgGroup) {
    for field in group.fields {
        show_field(&config, group.name, field);
    }
}

fn show_field(config: &KV, grpname: &str, field: &CfgField) {
    if field.is_silent() {
        return;
    }
    let key = field.full_key(grpname);
    println!("{}{}{} - {}", ANSI_FIELD, &key, ANSI_RESET, field.description());
    println!("  default: {}", field.default_description().unwrap_or(EMPTY_VALUE.to_string()));
    let value = config
        .get(&key)
        .ok()
        .map(|s| if field.is_password() { HIDDEN_PASSWORD.to_string() } else { s })
        .unwrap_or(EMPTY_VALUE.to_string());
    println!("  current: {}", value);
}

/* ***** basic validation ***** */

fn needs_info(config: &KV, group: &CfgGroup) -> Vec<String> {
    let mut acc = Vec::new();
    for field in group.fields {
        if field.is_action_required(config, group.name) {
            acc.push(field.key());
        }
    }
    acc
}

/* ***** prompting (with actual I/O) ***** */

/// Ask for a choice between several options.  First option is the default,
/// format options with the first character in brackets like so: `"[E]xample"`.
fn prompt_action(choices: &[&str]) -> char {
    let prompt_message = choices.join(", ");
    let default_choice = choices[0].to_uppercase().chars().nth(1).unwrap_or_default();
    loop {
        println!("{}", prompt_message);
        print!("Select: ");
        io::stdout().flush().ok();

        // Read line and take first non-space character
        let mut input = String::new();
        io::stdin().read_line(&mut input).unwrap();
        let input = input.trim().to_uppercase().chars().next().unwrap_or(default_choice);

        // Check list of choices for match
        if choices
            .iter()
            .any(|&choice| choice.to_uppercase().chars().nth(1).unwrap_or_default() == input)
        {
            return input;
        } else {
            println!("Invalid choice. Try again!");
        }
    }
}

/// Read a single line of text.
fn prompt_single_line() -> String {
    print!("New value: ");
    io::stdout().flush().ok();
    let mut input = String::new();
    io::stdin().read_line(&mut input).unwrap();
    input.trim().to_string()
}

/// Read multiple lines of text, terminated by a line containing just a '.'.
fn prompt_multiline() -> String {
    println!("Enter new value: (end with '.' on a new line)");
    let mut acc = String::new();
    loop {
        let mut line = String::new();
        io::stdin().read_line(&mut line).unwrap();
        if line.trim() == "." {
            break;
        }
        acc.push_str(&line);
    }
    acc
}

/// Read a password without echoing it.
fn prompt_password() -> String {
    let pass = rpassword::prompt_password("New password (not shown) : ").unwrap();
    // disabled echo means the newline also isn't shown
    println!("");
    pass
}