//! Machine-local user preferences and project-owned presentation settings.

use serde::{Deserialize, Serialize};

/// Preferred interface when a new human-facing agent terminal is opened.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub enum DefaultAgentTerminalInterface {
    /// Provider's native interactive terminal UI.
    NativeTui,
    /// IdeA's structured/custom CLI chat surface.
    IdeaCli,
}

/// User-selected IdeA interface language.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum IdeaLanguage {
    /// French interface.
    Fr,
    /// English interface.
    En,
}

/// Global, machine-local IdeA preferences.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct IdeaUserSettings {
    /// Default for newly launched human-facing agent terminals.
    #[serde(default)]
    pub default_agent_terminal_interface: Option<DefaultAgentTerminalInterface>,
    /// Preferred interface language. Absence preserves the product default.
    #[serde(default)]
    pub language: Option<IdeaLanguage>,
}

/// Supported icon catalogue for project visual identity.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "kebab-case")]
pub enum ProjectIconSet {
    /// Unicode emoji catalogue.
    Emoji,
    /// Devicon language and platform catalogue.
    Devicon,
    /// Simple Icons brand catalogue.
    SimpleIcons,
    /// Lucide general-purpose icon catalogue.
    Lucide,
    /// IdeA-owned built-in icons.
    Idea,
}

/// Maximum byte length of a stable project icon name.
pub const MAX_PROJECT_ICON_NAME_LEN: usize = 64;

/// Validated reference to one icon in a known catalogue.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase", try_from = "UncheckedProjectIconRef")]
pub struct ProjectIconRef {
    set: ProjectIconSet,
    name: String,
}

#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct UncheckedProjectIconRef {
    set: ProjectIconSet,
    name: String,
}

impl ProjectIconRef {
    /// Builds a validated stable icon reference.
    pub fn new(set: ProjectIconSet, name: impl Into<String>) -> Result<Self, String> {
        let name = name.into();
        let bytes = name.as_bytes();
        let valid_name = !name.is_empty()
            && name.len() <= MAX_PROJECT_ICON_NAME_LEN
            && bytes.first().is_some_and(u8::is_ascii_alphanumeric)
            && bytes.last().is_some_and(u8::is_ascii_alphanumeric)
            && bytes
                .iter()
                .copied()
                .all(|byte| byte.is_ascii_alphanumeric() || matches!(byte, b'-' | b'_' | b'.'));
        if !valid_name {
            return Err(format!(
                "project icon name must be 1..={MAX_PROJECT_ICON_NAME_LEN} ASCII letters, digits, '-', '_' or '.', starting and ending with a letter or digit"
            ));
        }
        Ok(Self { set, name })
    }

    /// Returns the owning icon catalogue.
    #[must_use]
    pub const fn set(&self) -> ProjectIconSet {
        self.set
    }

    /// Returns the stable catalogue icon name.
    #[must_use]
    pub fn name(&self) -> &str {
        &self.name
    }
}

impl TryFrom<UncheckedProjectIconRef> for ProjectIconRef {
    type Error = String;

    fn try_from(value: UncheckedProjectIconRef) -> Result<Self, Self::Error> {
        Self::new(value.set, value.name)
    }
}

/// Strict project theme colour (`#RRGGBB`).
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(try_from = "String", into = "String")]
pub struct ThemeColor(String);

impl ThemeColor {
    /// Validates and builds a project theme colour.
    pub fn new(value: impl Into<String>) -> Result<Self, String> {
        let value = value.into();
        let valid = value.len() == 7
            && value.starts_with('#')
            && value.as_bytes()[1..].iter().all(u8::is_ascii_hexdigit);
        valid
            .then_some(Self(value))
            .ok_or_else(|| "themeColor must match #RRGGBB".to_owned())
    }

    /// Returns the validated wire representation.
    #[must_use]
    pub fn as_str(&self) -> &str {
        &self.0
    }
}

impl TryFrom<String> for ThemeColor {
    type Error = String;

    fn try_from(value: String) -> Result<Self, Self::Error> {
        Self::new(value)
    }
}

impl From<ThemeColor> for String {
    fn from(value: ThemeColor) -> Self {
        value.0
    }
}

/// Settings owned by one project and stored below its `.ideai` directory.
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct ProjectSettings {
    /// Optional visual theme colour; absence keeps the product fallback.
    #[serde(default)]
    pub theme_color: Option<ThemeColor>,
    /// Optional validated icon used as the project's visual identity.
    #[serde(default)]
    pub icon: Option<ProjectIconRef>,
}