use std::{
    ffi::c_void,
    os::windows::process::CommandExt,
    path::{Path, PathBuf},
    process::Command,
};
use windows_sys::Win32::{
    Foundation::ERROR_SUCCESS,
    System::Registry::{
        HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, REG_EXPAND_SZ, REG_SZ, RRF_RT_REG_EXPAND_SZ,
        RRF_RT_REG_SZ, RegGetValueW,
    },
};

pub fn check_windows_app(app_name: &str) -> bool {
    resolve_windows_app_path(app_name).is_some()
}

pub fn resolve_windows_app_path(app_name: &str) -> Option<String> {
    fn expand_env(value: &str) -> String {
        let mut out = String::with_capacity(value.len());
        let mut index = 0;

        while let Some(start) = value[index..].find('%') {
            let start = index + start;
            out.push_str(&value[index..start]);

            let Some(end_rel) = value[start + 1..].find('%') else {
                out.push_str(&value[start..]);
                return out;
            };

            let end = start + 1 + end_rel;
            let key = &value[start + 1..end];
            if key.is_empty() {
                out.push('%');
                index = end + 1;
                continue;
            }

            if let Ok(v) = std::env::var(key) {
                out.push_str(&v);
                index = end + 1;
                continue;
            }

            out.push_str(&value[start..=end]);
            index = end + 1;
        }

        out.push_str(&value[index..]);
        out
    }

    fn extract_exe(value: &str) -> Option<String> {
        let value = value.trim();
        if value.is_empty() {
            return None;
        }

        if let Some(rest) = value.strip_prefix('"') {
            if let Some(end) = rest.find('"') {
                let inner = rest[..end].trim();
                if inner.to_ascii_lowercase().contains(".exe") {
                    return Some(inner.to_string());
                }
            }
        }

        let lower = value.to_ascii_lowercase();
        let end = lower.find(".exe")?;
        Some(value[..end + 4].trim().trim_matches('"').to_string())
    }

    fn candidates(app_name: &str) -> Vec<String> {
        let app_name = app_name.trim().trim_matches('"');
        if app_name.is_empty() {
            return vec![];
        }

        let mut out = Vec::<String>::new();
        let mut push = |value: String| {
            let value = value.trim().trim_matches('"').to_string();
            if value.is_empty() {
                return;
            }
            if out.iter().any(|v| v.eq_ignore_ascii_case(&value)) {
                return;
            }
            out.push(value);
        };

        push(app_name.to_string());

        let lower = app_name.to_ascii_lowercase();
        if !lower.ends_with(".exe") {
            push(format!("{app_name}.exe"));
        }

        let snake = {
            let mut s = String::new();
            let mut underscore = false;
            for c in lower.chars() {
                if c.is_ascii_alphanumeric() {
                    s.push(c);
                    underscore = false;
                    continue;
                }
                if underscore {
                    continue;
                }
                s.push('_');
                underscore = true;
            }
            s.trim_matches('_').to_string()
        };

        if !snake.is_empty() {
            push(snake.clone());
            if !snake.ends_with(".exe") {
                push(format!("{snake}.exe"));
            }
        }

        let alnum = lower
            .chars()
            .filter(|c| c.is_ascii_alphanumeric())
            .collect::<String>();

        if !alnum.is_empty() {
            push(alnum.clone());
            push(format!("{alnum}.exe"));
        }

        match lower.as_str() {
            "sublime text" | "sublime-text" | "sublime_text" | "sublime text.exe" => {
                push("subl".to_string());
                push("subl.exe".to_string());
                push("sublime_text".to_string());
                push("sublime_text.exe".to_string());
            }
            _ => {}
        }

        out
    }

    fn reg_app_path(exe: &str) -> Option<String> {
        let exe = exe.trim().trim_matches('"');
        if exe.is_empty() {
            return None;
        }

        let query = |root: *mut c_void, subkey: &str| -> Option<String> {
            let flags = RRF_RT_REG_SZ | RRF_RT_REG_EXPAND_SZ;
            let mut kind: u32 = 0;
            let mut size = 0u32;

            let mut key = subkey.encode_utf16().collect::<Vec<_>>();
            key.push(0);

            let status = unsafe {
                RegGetValueW(
                    root,
                    key.as_ptr(),
                    std::ptr::null(),
                    flags,
                    &mut kind,
                    std::ptr::null_mut(),
                    &mut size,
                )
            };

            if status != ERROR_SUCCESS || size == 0 {
                return None;
            }

            if kind != REG_SZ && kind != REG_EXPAND_SZ {
                return None;
            }

            let mut data = vec![0u8; size as usize];
            let status = unsafe {
                RegGetValueW(
                    root,
                    key.as_ptr(),
                    std::ptr::null(),
                    flags,
                    &mut kind,
                    data.as_mut_ptr() as *mut c_void,
                    &mut size,
                )
            };

            if status != ERROR_SUCCESS || size < 2 {
                return None;
            }

            let words = unsafe {
                std::slice::from_raw_parts(data.as_ptr().cast::<u16>(), (size as usize) / 2)
            };
            let len = words.iter().position(|v| *v == 0).unwrap_or(words.len());
            let value = String::from_utf16_lossy(&words[..len]).trim().to_string();

            if value.is_empty() {
                return None;
            }

            Some(value)
        };

        let keys = [
            (
                HKEY_CURRENT_USER,
                format!(r"Software\Microsoft\Windows\CurrentVersion\App Paths\{exe}"),
            ),
            (
                HKEY_LOCAL_MACHINE,
                format!(r"Software\Microsoft\Windows\CurrentVersion\App Paths\{exe}"),
            ),
            (
                HKEY_LOCAL_MACHINE,
                format!(r"Software\WOW6432Node\Microsoft\Windows\CurrentVersion\App Paths\{exe}"),
            ),
        ];

        for (root, key) in keys {
            let Some(value) = query(root, &key) else {
                continue;
            };

            let Some(exe) = extract_exe(&value) else {
                continue;
            };

            let exe = expand_env(&exe);
            let path = Path::new(exe.trim().trim_matches('"'));
            if path.exists() {
                return Some(path.to_string_lossy().to_string());
            }
        }

        None
    }

    let app_name = app_name.trim().trim_matches('"');
    if app_name.is_empty() {
        return None;
    }

    let direct = Path::new(app_name);
    if direct.is_absolute() && direct.exists() {
        return Some(direct.to_string_lossy().to_string());
    }

    let key = app_name
        .chars()
        .filter(|v| v.is_ascii_alphanumeric())
        .flat_map(|v| v.to_lowercase())
        .collect::<String>();

    let has_ext = |path: &Path, ext: &str| {
        path.extension()
            .and_then(|v| v.to_str())
            .map(|v| v.eq_ignore_ascii_case(ext))
            .unwrap_or(false)
    };

    let resolve_cmd = |path: &Path| -> Option<String> {
        let bytes = std::fs::read(path).ok()?;
        let content = String::from_utf8_lossy(&bytes);

        for token in content.split('"') {
            let Some(exe) = extract_exe(token) else {
                continue;
            };

            let lower = exe.to_ascii_lowercase();
            if let Some(index) = lower.find("%~dp0") {
                let base = path.parent()?;
                let suffix = &exe[index + 5..];
                let mut resolved = PathBuf::from(base);

                for part in suffix.replace('/', "\\").split('\\') {
                    if part.is_empty() || part == "." {
                        continue;
                    }
                    if part == ".." {
                        let _ = resolved.pop();
                        continue;
                    }
                    resolved.push(part);
                }

                if resolved.exists() {
                    return Some(resolved.to_string_lossy().to_string());
                }

                continue;
            }

            let resolved = PathBuf::from(expand_env(&exe));
            if resolved.exists() {
                return Some(resolved.to_string_lossy().to_string());
            }
        }

        None
    };

    let resolve_where = |query: &str| -> Option<String> {
        let output = Command::new("where")
            .creation_flags(0x08000000)
            .arg(query)
            .output()
            .ok()?;
        if !output.status.success() {
            return None;
        }

        let paths = String::from_utf8_lossy(&output.stdout)
            .lines()
            .map(str::trim)
            .filter(|line| !line.is_empty())
            .map(PathBuf::from)
            .collect::<Vec<_>>();

        if paths.is_empty() {
            return None;
        }

        if let Some(path) = paths.iter().find(|path| has_ext(path, "exe")) {
            return Some(path.to_string_lossy().to_string());
        }

        for path in &paths {
            if has_ext(path, "cmd") || has_ext(path, "bat") {
                if let Some(resolved) = resolve_cmd(path) {
                    return Some(resolved);
                }
            }

            if path.extension().is_none() {
                let cmd = path.with_extension("cmd");
                if cmd.exists() {
                    if let Some(resolved) = resolve_cmd(&cmd) {
                        return Some(resolved);
                    }
                }

                let bat = path.with_extension("bat");
                if bat.exists() {
                    if let Some(resolved) = resolve_cmd(&bat) {
                        return Some(resolved);
                    }
                }
            }
        }

        if !key.is_empty() {
            for path in &paths {
                let dirs = [
                    path.parent(),
                    path.parent().and_then(|dir| dir.parent()),
                    path.parent()
                        .and_then(|dir| dir.parent())
                        .and_then(|dir| dir.parent()),
                ];

                for dir in dirs.into_iter().flatten() {
                    if let Ok(entries) = std::fs::read_dir(dir) {
                        for entry in entries.flatten() {
                            let candidate = entry.path();
                            if !has_ext(&candidate, "exe") {
                                continue;
                            }

                            let Some(stem) = candidate.file_stem().and_then(|v| v.to_str()) else {
                                continue;
                            };

                            let name = stem
                                .chars()
                                .filter(|v| v.is_ascii_alphanumeric())
                                .flat_map(|v| v.to_lowercase())
                                .collect::<String>();

                            if name.contains(&key) || key.contains(&name) {
                                return Some(candidate.to_string_lossy().to_string());
                            }
                        }
                    }
                }
            }
        }

        paths.first().map(|path| path.to_string_lossy().to_string())
    };

    let list = candidates(app_name);
    for query in &list {
        if let Some(path) = resolve_where(query) {
            return Some(path);
        }
    }

    let mut exes = Vec::<String>::new();
    for query in &list {
        let query = query.trim().trim_matches('"');
        if query.is_empty() {
            continue;
        }

        let name = Path::new(query)
            .file_name()
            .and_then(|v| v.to_str())
            .unwrap_or(query);

        let exe = if name.to_ascii_lowercase().ends_with(".exe") {
            name.to_string()
        } else {
            format!("{name}.exe")
        };

        if exes.iter().any(|v| v.eq_ignore_ascii_case(&exe)) {
            continue;
        }

        exes.push(exe);
    }

    for exe in exes {
        if let Some(path) = reg_app_path(&exe) {
            return Some(path);
        }
    }

    None
}