use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct Theme {
    pub name: &'static str,
    pub fg: &'static str,
    pub bg: &'static str,
    pub ansi_normal: [&'static str; 8],
    pub ansi_bright: [&'static str; 8],
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[allow(dead_code)]
pub struct ANSIPalette {
    pub name: &'static str,
    pub ansi_normal: [&'static str; 8],
    pub ansi_bright: [&'static str; 8],
}

impl Theme {
    pub fn to_css_block(&self) -> String {
        let (btn_primary_bg, btn_primary_fg) = self.button_colors(4);
        let (btn_danger_bg, btn_danger_fg) = self.button_colors(1);
        format!(
            ":root {{\n\
               --app-fg: {};\n\
               --app-bg: {};\n\
               --ui-border: {}33;\n\
               --ui-hover: {}1a;\n\
               --btn-primary-bg: {};\n\
               --btn-primary-fg: {};\n\
               --btn-danger-bg: {};\n\
               --btn-danger-fg: {};\n\
               --ansi-0: {}; --ansi-1: {}; --ansi-2: {}; --ansi-3: {};\n\
               --ansi-4: {}; --ansi-5: {}; --ansi-6: {}; --ansi-7: {};\n\
               --ansi-8: {}; --ansi-9: {}; --ansi-10: {}; --ansi-11: {};\n\
               --ansi-12: {}; --ansi-13: {}; --ansi-14: {}; --ansi-15: {};\n\
             }}",
            self.fg,
            self.bg,
            self.fg,
            self.fg,
            btn_primary_bg,
            btn_primary_fg,
            btn_danger_bg,
            btn_danger_fg,
            self.ansi_normal[0],
            self.ansi_normal[1],
            self.ansi_normal[2],
            self.ansi_normal[3],
            self.ansi_normal[4],
            self.ansi_normal[5],
            self.ansi_normal[6],
            self.ansi_normal[7],
            self.ansi_bright[0],
            self.ansi_bright[1],
            self.ansi_bright[2],
            self.ansi_bright[3],
            self.ansi_bright[4],
            self.ansi_bright[5],
            self.ansi_bright[6],
            self.ansi_bright[7],
        )
    }

    fn button_colors(&self, accent: usize) -> (&'static str, &'static str) {
        // Use the bright variant of the accent color if it has decent luminance;
        // otherwise fall back to the theme foreground color so text remains readable.
        let bright = self.ansi_bright[accent];
        if relative_luminance(bright) < 0.15 {
            (self.fg, self.bg)
        } else {
            (bright, self.bg)
        }
    }
}

fn relative_luminance(hex: &str) -> f64 {
    let hex = hex.trim_start_matches('#');
    if hex.len() != 6 {
        return 0.0;
    }
    let r = u8::from_str_radix(&hex[0..2], 16).unwrap_or(0) as f64 / 255.0;
    let g = u8::from_str_radix(&hex[2..4], 16).unwrap_or(0) as f64 / 255.0;
    let b = u8::from_str_radix(&hex[4..6], 16).unwrap_or(0) as f64 / 255.0;
    0.2126 * r + 0.7152 * g + 0.0722 * b
}

pub static PREDEFINED_THEMES: &[Theme] = &[
    Theme {
        name: "Dark",
        fg: "#d0d0d0",
        bg: "#1c1c1c",
        ansi_normal: [
            "#1c1c1c", "#c50f1f", "#23a523", "#b58900", "#268bd2", "#d33682", "#2aa198", "#d0d0d0",
        ],
        ansi_bright: [
            "#666666", "#ff6666", "#66ff66", "#ffff66", "#6666ff", "#ff66ff", "#66ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Light",
        fg: "#1c1c1c",
        bg: "#d0d0d0",
        ansi_normal: [
            "#1c1c1c", "#c50f1f", "#23a523", "#b58900", "#268bd2", "#d33682", "#2aa198", "#d0d0d0",
        ],
        ansi_bright: [
            "#666666", "#ff6666", "#66ff66", "#ffff66", "#6666ff", "#ff66ff", "#66ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Solarized Dark",
        fg: "#839496",
        bg: "#002b36",
        ansi_normal: [
            "#073642", "#dc322f", "#859900", "#b58900", "#268bd2", "#d33682", "#2aa198", "#eee8d5",
        ],
        ansi_bright: [
            "#002b36", "#cb4b16", "#586e75", "#657b83", "#839496", "#6c71c4", "#93a1a1", "#fdf6e3",
        ],
    },
    Theme {
        name: "Solarized Light",
        fg: "#657b83",
        bg: "#fdf6e3",
        ansi_normal: [
            "#073642", "#dc322f", "#859900", "#b58900", "#268bd2", "#d33682", "#2aa198", "#eee8d5",
        ],
        ansi_bright: [
            "#002b36", "#cb4b16", "#586e75", "#657b83", "#839496", "#6c71c4", "#93a1a1", "#fdf6e3",
        ],
    },
    Theme {
        name: "Dracula",
        fg: "#f8f8f2",
        bg: "#282a36",
        ansi_normal: [
            "#21222c", "#ff5555", "#50fa7b", "#f1fa8c", "#bd93f9", "#ff79c6", "#8be9fd", "#f8f8f2",
        ],
        ansi_bright: [
            "#6272a4", "#ff6e6e", "#69ff94", "#ffffa5", "#d6acff", "#ff92df", "#a4ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Gruvbox Dark",
        fg: "#ebdbb2",
        bg: "#282828",
        ansi_normal: [
            "#282828", "#cc241d", "#98971a", "#d79921", "#458588", "#b16286", "#689d6a", "#a89984",
        ],
        ansi_bright: [
            "#928374", "#fb4934", "#b8bb26", "#fabd2f", "#83a598", "#d3869b", "#8ec07c", "#ebdbb2",
        ],
    },
    Theme {
        name: "Gruvbox Light",
        fg: "#3c3836",
        bg: "#fbf1c7",
        ansi_normal: [
            "#fbf1c7", "#cc241d", "#98971a", "#d79921", "#458588", "#b16286", "#689d6a", "#7c6f64",
        ],
        ansi_bright: [
            "#928374", "#9d0006", "#79740e", "#b57614", "#076678", "#8f3f71", "#427b58", "#3c3836",
        ],
    },
    Theme {
        name: "Nord",
        fg: "#d8dee9",
        bg: "#2e3440",
        ansi_normal: [
            "#3b4252", "#bf616a", "#a3be8c", "#ebcb8b", "#81a1c1", "#b48ead", "#88c0d0", "#e5e9f0",
        ],
        ansi_bright: [
            "#4c566a", "#bf616a", "#a3be8c", "#ebcb8b", "#81a1c1", "#b48ead", "#8fbcbb", "#eceff4",
        ],
    },
    Theme {
        name: "Monokai",
        fg: "#f8f8f2",
        bg: "#272822",
        ansi_normal: [
            "#272822", "#f92672", "#a6e22e", "#f4bf75", "#66d9ef", "#ae81ff", "#a1efe4", "#f8f8f2",
        ],
        ansi_bright: [
            "#75715e", "#f92672", "#a6e22e", "#e6db74", "#66d9ef", "#ae81ff", "#a1efe4", "#f9f8f5",
        ],
    },
    Theme {
        name: "Tokyo Night",
        fg: "#c0caf5",
        bg: "#1a1b26",
        ansi_normal: [
            "#15161e", "#f7768e", "#9ece6a", "#e0af68", "#7aa2f7", "#bb9af7", "#7dcfff", "#a9b1d6",
        ],
        ansi_bright: [
            "#414868", "#f7768e", "#9ece6a", "#e0af68", "#7aa2f7", "#bb9af7", "#7dcfff", "#c0caf5",
        ],
    },
    Theme {
        name: "One Dark",
        fg: "#abb2bf",
        bg: "#282c34",
        ansi_normal: [
            "#282c34", "#e06c75", "#98c379", "#e5c07b", "#61afef", "#c678dd", "#56b6c2", "#abb2bf",
        ],
        ansi_bright: [
            "#5c6370", "#e06c75", "#98c379", "#e5c07b", "#61afef", "#c678dd", "#56b6c2", "#ffffff",
        ],
    },
    Theme {
        name: "Cyberpunk 2077",
        fg: "#f9f227",
        bg: "#0d0d0d",
        ansi_normal: [
            "#0d0d0d", "#ff0055", "#00ff41", "#f9f227", "#00b8ff", "#ff00cc", "#00ffff", "#f9f227",
        ],
        ansi_bright: [
            "#333333", "#ff3377", "#33ff66", "#ffff33", "#33ccff", "#ff33ff", "#33ffff", "#ffff66",
        ],
    },
    Theme {
        name: "Cyan on Black",
        fg: "#00ffff",
        bg: "#000000",
        ansi_normal: [
            "#000000", "#cc0000", "#00cc00", "#cccc00", "#0000cc", "#cc00cc", "#00cccc", "#cccccc",
        ],
        ansi_bright: [
            "#666666", "#ff0000", "#00ff00", "#ffff00", "#a9a9f9", "#ff00ff", "#00ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Red on Black",
        fg: "#ff0000",
        bg: "#000000",
        ansi_normal: [
            "#000000", "#cc0000", "#00cc00", "#cccc00", "#0000cc", "#cc00cc", "#00cccc", "#cccccc",
        ],
        ansi_bright: [
            "#666666", "#ff0000", "#00ff00", "#ffff00", "#a9a9f9", "#ff00ff", "#00ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Lime Green on Black",
        fg: "#00ff00",
        bg: "#000000",
        ansi_normal: [
            "#000000", "#cc0000", "#00cc00", "#cccc00", "#0000cc", "#cc00cc", "#00cccc", "#cccccc",
        ],
        ansi_bright: [
            "#666666", "#ff0000", "#00ff00", "#ffff00", "#a9a9f9", "#ff00ff", "#00ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Chartreuse on Black",
        fg: "#7fff00",
        bg: "#000000",
        ansi_normal: [
            "#000000", "#cc0000", "#00cc00", "#cccc00", "#0000cc", "#cc00cc", "#00cccc", "#cccccc",
        ],
        ansi_bright: [
            "#666666", "#ff0000", "#00ff00", "#ffff00", "#a9a9f9", "#ff00ff", "#00ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Amber on Black",
        fg: "#ffbf00",
        bg: "#000000",
        ansi_normal: [
            "#000000", "#cc0000", "#00cc00", "#cccc00", "#0000cc", "#cc00cc", "#00cccc", "#cccccc",
        ],
        ansi_bright: [
            "#666666", "#ff0000", "#00ff00", "#ffff00", "#a9a9f9", "#ff00ff", "#00ffff", "#ffffff",
        ],
    },
    Theme {
        name: "Blueberry on Black",
        fg: "#8ec5fc",
        bg: "#000000",
        ansi_normal: [
            "#000000", "#0d47a1", "#1565c0", "#1976d2", "#1e88e5", "#42a5f5", "#64b5f6", "#90caf9",
        ],
        ansi_bright: [
            "#37474f", "#1e88e5", "#42a5f5", "#64b5f6", "#90caf9", "#bbdefb", "#e3f2fd", "#ffffff",
        ],
    },
    Theme {
        name: "Spring Blossom",
        fg: "#ffb7c5",
        bg: "#2d5016",
        ansi_normal: [
            "#2d5016", "#c2185b", "#7cb342", "#fbc02d", "#00897b", "#d81b60", "#aed581", "#f8bbd0",
        ],
        ansi_bright: [
            "#558b2f", "#e91e63", "#8bc34a", "#ffeb3b", "#009688", "#ec407a", "#c5e1a5", "#fce4ec",
        ],
    },
    Theme {
        name: "Summer Sunset",
        fg: "#ff9a5a",
        bg: "#1a1a2e",
        ansi_normal: [
            "#1a1a2e", "#e64a19", "#ff7043", "#ffab40", "#d81b60", "#8e24aa", "#5c6bc0", "#ffb74d",
        ],
        ansi_bright: [
            "#424242", "#ff5722", "#ff8a65", "#ffc107", "#e91e63", "#9c27b0", "#3f51b5", "#ffe0b2",
        ],
    },
    Theme {
        name: "Autumn Forest",
        fg: "#d4a373",
        bg: "#3e2723",
        ansi_normal: [
            "#3e2723", "#bf360c", "#e65100", "#8d6e63", "#5d4037", "#33691e", "#9e9d24", "#a1887f",
        ],
        ansi_bright: [
            "#6d4c41", "#e64a19", "#f57c00", "#a1887f", "#795548", "#558b2f", "#c0ca33", "#d7ccc8",
        ],
    },
    Theme {
        name: "Winter Frost",
        fg: "#e0f7fa",
        bg: "#1a237e",
        ansi_normal: [
            "#1a237e", "#006064", "#00838f", "#0097a7", "#00acc1", "#26c6da", "#4dd0e1", "#80deea",
        ],
        ansi_bright: [
            "#283593", "#00897b", "#00acc1", "#26c6da", "#4dd0e1", "#80deea", "#b2ebf2", "#ffffff",
        ],
    },
    Theme {
        name: "Stormy Night",
        fg: "#b0bec5",
        bg: "#263238",
        ansi_normal: [
            "#263238", "#37474f", "#455a64", "#546e7a", "#607d8b", "#78909c", "#90a4ae", "#b0bec5",
        ],
        ansi_bright: [
            "#455a64", "#607d8b", "#78909c", "#90a4ae", "#b0bec5", "#cfd8dc", "#eceff1", "#ffffff",
        ],
    },
    Theme {
        name: "Sunny Day",
        fg: "#fff59d",
        bg: "#33691e",
        ansi_normal: [
            "#33691e", "#f57f17", "#c0ca33", "#00acc1", "#00897b", "#5c6bc0", "#7cb342", "#fff59d",
        ],
        ansi_bright: [
            "#558b2f", "#fbc02d", "#afb42b", "#26c6da", "#0097a7", "#3f51b5", "#9ccc65", "#fff9c4",
        ],
    },
    Theme {
        name: "Foggy Morning",
        fg: "#cfd8dc",
        bg: "#455a64",
        ansi_normal: [
            "#455a64", "#546e7a", "#607d8b", "#78909c", "#90a4ae", "#b0bec5", "#cfd8dc", "#eceff1",
        ],
        ansi_bright: [
            "#607d8b", "#78909c", "#90a4ae", "#b0bec5", "#cfd8dc", "#eceff1", "#f5f5f5", "#ffffff",
        ],
    },
];

pub fn get_theme(name: &str) -> &'static Theme {
    PREDEFINED_THEMES
        .iter()
        .find(|t| t.name == name)
        .unwrap_or(&PREDEFINED_THEMES[0])
}

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

    #[test]
    fn default_theme_is_dark() {
        let theme = get_theme("Nonexistent");
        assert_eq!(theme.name, "Dark");
    }

    #[test]
    fn css_block_contains_variables() {
        let theme = get_theme("Dark");
        let css = theme.to_css_block();
        assert!(css.contains("--app-fg:"));
        assert!(css.contains("--app-bg:"));
        assert!(css.contains("--btn-primary-bg:"));
        assert!(css.contains("--btn-danger-bg:"));
        assert!(css.contains("--ansi-0:"));
        assert!(css.contains("--ansi-15:"));
    }

    #[test]
    fn dark_themes_use_readable_button_colors() {
        // Bright accent colors should be luminous enough to use as button
        // backgrounds; very dark accents fall back to the theme foreground.
        let cyan = get_theme("Cyan on Black");
        let (bg, fg) = cyan.button_colors(4);
        // After replacing #0000ff with #a9a9f9, the bright blue is readable
        // and no longer falls back to the foreground color.
        assert_eq!(bg, cyan.ansi_bright[4]);
        assert_eq!(fg, cyan.bg);
    }

    #[test]
    fn all_themes_have_sixteen_ansi_colors() {
        for theme in PREDEFINED_THEMES {
            assert_eq!(theme.ansi_normal.len(), 8);
            assert_eq!(theme.ansi_bright.len(), 8);
        }
    }
}