use anyhow::{Context, Result, bail};
use cache::relative_to_absolute;
use clap::{Parser, Subcommand};
use std::collections::HashMap;
// use std::env;
use std::env;
use std::fs::{File, create_dir_all, read_dir, remove_dir_all, set_permissions};
use std::io::{BufRead, BufReader};
use std::path::PathBuf;
use std::process::Command;
use std::time::Duration;

mod cache;

#[derive(Parser)]
#[command(
    about = "Go Updater",
    long_about = "Go Updater

This checks https://go.dev/dl for newer versions of go.
It depends upon go being in the path, and optionally GOPATH being set.

This can't update a package manager installed version of go (permissions)."
)]
struct Cli {
    /*
    /// Cache directory path
    #[arg(short, long, default_value = "cache")]
    cache: PathBuf,
    */
    #[command(subcommand)]
    command: Option<Commands>,
}

#[derive(Subcommand)]
enum Commands {
    /// Update go
    Update {},
    /// Display information
    Info {},
}

/// Query `go env`
///
/// This is a good example of parsing output line by line.
#[must_use]
fn get_go_env() -> Result<HashMap<String, String>> {
    let output = Command::new("go").arg("env").output()?;
    if output.status.success() {
        let mut result = HashMap::<String, String>::new();

        let output_str = std::str::from_utf8(output.stdout.as_slice())?;
        for mut line in output_str.split("\n") {
            line = line.trim();
            if let Some(parts) = line.split_once("=") {
                let value = parts.1.trim_matches('\'');
                result.insert(parts.0.to_string(), value.to_string());
            }
        }
        /*
        for mut line in String::from_utf8_lossy(output.stdout.as_slice()).split("\n") {
        }
        */
        Ok(result)
    } else {
        bail!("Failed to query `go env`");
    }
}

fn extract_tarball(tarball: &str, target: &str) -> Result<()> {
    println!("Extract {} to {}", tarball, target);
    let output = Command::new("tar")
        // Extract, gzipped, from file
        .arg("-xzf")
        .arg(tarball)
        // archive contains go directory. Strip that out.
        .arg("--strip-components=1")
        // Set target to extract to.
        .arg("-C")
        .arg(target)
        .output()?;
    if output.status.success() {
        return Ok(());
    }
    bail!("Extract {} failed.", tarball);
}

/*
/// Query `go version`
#[must_use]
#[allow(dead_code)]
#[deprecated = "Use get_go_env"]
fn find_go_version() -> Result<String> {
    let output = Command::new("go").arg("version").output()?;
    if output.status.success() {
        // Ok! We have something!
        return Ok(String::from_utf8_lossy(output.stdout.as_slice()).to_string());
    }
    bail!("Failed to query go version.");
}
*/

/*
/// Locate the go binary
///
/// This is redundant, it should be located via GO_PATH.
#[allow(dead_code)]
#[must_use]
fn find_go() -> Result<String> {
    let output = Command::new("which").arg("go").output()?;
    if output.status.success() {
        return Ok(String::from_utf8_lossy(output.stdout.as_slice()).to_string());
    }
    bail!("Failed to locate go binary.");
}
*/

const GO_URL: &str = "https://go.dev/dl/";

// static APP_USER_AGENT: &str = concat!(env!("CARGO_PKG_NAME"), "/", env!("CARGO_PKG_VERSION"),);

// I've changed the parser, so scrapy isn't needed.
// I'll revisit this when I get further with html tokeparser.

/*
CSS Selector elements of interest:  (a href="" part).
href are relative...

div[class="downloadWrapper"] > a[class="download downloadBox"]

<a class="download downloadBox" href="/dl/go1.24.0.windows-amd64.msi">
<a class="download downloadBox" href="/dl/go1.24.0.linux-amd64.tar.gz">

table[class="downloadtable"] > tr[class=" "] > td[class="filename"] > a[class="download"]

Or possibly,

table[class="downloadtable"] > tr[class=" "]
or tr[class="highlight "] ?
and grab the section of td's.  class=filename has a href, last has SHA256.

<a class="download" href="/dl/go1.24.0.src.tar.gz">go1.24.0.src.tar.gz</a>
<a class="download" href="/dl/go1.24.0.linux-amd64.tar.gz">go1.24.0.linux-amd64.tar.gz</a>
<a class="download" href="/dl/go1.24.0.linux-arm64.tar.gz">go1.24.0.linux-arm64.tar.gz</a>
<a class="download" href="/dl/go1.24.0.windows-amd64.zip">go1.24.0.windows-amd64.zip</a>
<a class="download" href="/dl/go1.24.0.windows-amd64.msi">go1.24.0.windows-amd64.msi</a>
 */

// URL: https://go.dev/dl/go1.24.1.linux-amd64.tar.gz

/// Get go version from download link.
///
/// Given https://go.dev/dl/go1.24.1.linux-amd64.tar.gz
/// return "1.24.1" version part.
#[must_use]
fn version_from_url(url: &str, arch: &str) -> Option<String> {
    if let Some(parts) = url.split_once(arch) {
        if let Some(part) = parts.0.rsplit_once("/go") {
            let part = part.1.trim_matches('.');
            return Some(part.to_string());
        }
    }
    None
}

/// Return just the href="<return just this part>".
#[must_use]
fn just_href(link: &str) -> Result<String> {
    let parts = link.split_once("href=\"").unwrap_or(("", "")).1;
    let href = parts.split_once("\"").unwrap_or(("", "")).0;
    if !href.is_empty() {
        return Ok(href.to_string());
    }
    bail!("Unable to locate href");
}

/// Find a href link for given os and arch (architecture) in a file.
///
/// Look for a line with <a class="download" href="
#[must_use]
fn find_arch_link(os_arch: &str, fp: &File) -> Result<String> {
    let reader = BufReader::new(fp);
    for line in reader.lines() {
        if let Ok(line) = line {
            if line.contains("a class=\"download\"") {
                if line.contains(os_arch) {
                    // Return just the href part.
                    return just_href(&line);
                }
            }
        }
    }
    bail!("Unable to locate OS architecture download link");
}

/*
// This is terrible, since it has all of the HTML in a string.

/// find_link for given arch (architecture)
///
/// Look for <a class="download" href=""
#[must_use]
#[deprecated = "Use find_arch_link don't store the HTML in memory."]
fn find_link(arch: &str) -> Result<String> {
    // , Box<dyn Error>> {
    let fp = File::open(GO_FILE)?;
    let reader = BufReader::new(fp);
    for line in reader.lines() {
        if let Ok(line) = line {
            if line.contains("a class=\"download\"") {
                if line.contains(arch) {
                    // Return just the href part.
                    return just_href(&line);
                }
            }
        }
    }
    bail!("Unable to locate architecture download link");
}
*/

/// Get value from given HashMap<String,String>
///
/// This gives us a String, not a &String, and not an Option.
/// Returns empty String if key not found.
fn hashget(hash: &HashMap<String, String>, key: &str) -> String {
    if let Some(value) = hash.get(key) {
        return value.clone();
    }
    String::new()
}

fn recursive_remove_readonly(path: &str) -> Result<bool> {
    let mut result: bool = false;
    for entry in read_dir(path)? {
        let fsentry = entry?;
        if let Ok(meta) = fsentry.metadata() {
            if meta.is_dir() {
                if let Ok(r) =
                    recursive_remove_readonly(&fsentry.path().to_string_lossy().to_string())
                {
                    if r {
                        result = true;
                    }
                }
            }
            if meta.permissions().readonly() {
                // println!("Fixing: {}", fsentry.path().display());
                let mut read = meta.permissions();
                read.set_readonly(false);
                // Ok, this is marked readonly, change it.
                set_permissions(fsentry.path(), read)?;
                result = true;
            }
        }
    }
    Ok(result)
}

fn main() -> Result<()> {
    let cli = Cli::parse();

    // Construct cache_dir from HOME/~
    let home = env::var("HOME")?;
    let cache_dir = format!("{home}/.cache/go-up");

    /*
    GOROOT, defaults to $HOME/go
    This seems to be managed by go now.  So running ```go env``` would
    have/show GOROOT being set by that instance of go.
    GOPATH is another story.  It's where go stores things it downloads from
    the web, and most certainly shouldn't be $HOME/go != GOROOT.

    I want to be a bit looser on requiring GOROOT later on.
    */

    /*
    // Get go environment
    // The old way of doing this.  Using `go env` now.
    let go_path = env::var("GOPATH").unwrap_or(String::new());
    let go_root = env::var("GOROOT").unwrap_or(String::new());
    */

    let go_env = get_go_env().context("Calling `go env` failed.")?;
    let mut go_version = hashget(&go_env, "GOVERSION");
    if go_version.starts_with("go") {
        go_version.remove(0);
        go_version.remove(0);
    }

    let go_arch = hashget(&go_env, "GOARCH");
    let go_os = hashget(&go_env, "GOOS");
    let go_path = hashget(&go_env, "GOPATH");
    let go_root = hashget(&go_env, "GOROOT");
    // Construct OS-ARCH value.
    let go_os_arch = format!("{go_os}-{go_arch}");

    // Initialize the cache.
    let cache = cache::Cache::new(PathBuf::from(cache_dir), None)?;
    let ex = cache.expire(Duration::from_secs(7 * 60 * 60 * 24))?;
    if ex {
        println!("Expired files from cache.");
    }

    match &cli.command {
        Some(Commands::Update {}) => {
            let status = cache.fetch(GO_URL)?;

            // Check to see if file already exists AND check version against go's version.
            // Since the go.dev site doesn't allow caching or knowing when it changes,
            // we always end up in Status::Fetched arm.

            let filename = status.download_path();

            // Make this function the same whether or not we have a cache hit.

            let fp = File::open(filename)?;
            let link = find_arch_link(&go_os_arch, &fp);

            if let Ok(relative) = link {
                // Download link for arch located.  Make absolute URL.
                let latest_version = version_from_url(&relative, &go_os_arch);
                if let Some(latest) = latest_version {
                    println!("Version: {} [have {}]", latest, go_version);
                    if go_version != latest {
                        println!("Downloading newer version...");
                        let abs = relative_to_absolute(GO_URL, &relative).unwrap();

                        let latest_status = cache.fetch(&abs)?;
                        let update = latest_status.download_path();

                        println!("Clearing GOROOT {}", go_root);

                        // GOROOT might contain GOPATH files
                        // Fix permissions before attempting to remove.
                        recursive_remove_readonly(&go_path)?;
                        remove_dir_all(&go_root)?;
                        create_dir_all(&go_root)?;

                        if !go_path.is_empty() {
                            if go_path != go_root {
                                println!("Clearing GOPATH {}", go_path);
                                // This fails with permissions error
                                recursive_remove_readonly(&go_path)?;
                                remove_dir_all(&go_path)?;
                                create_dir_all(&go_path)?;
                            }
                        }

                        println!("Extracting...");
                        extract_tarball(&update.to_string_lossy().to_string(), &go_root)?;
                        // Extract go.tar.gz into go_root

                        // Ok, we have the update!  Now what?
                        // Verify new GO version!
                        let new_go_env = get_go_env().context("Calling `go env` with new go.")?;
                        let mut new_go_version = hashget(&new_go_env, "GOVERSION");
                        if new_go_version.starts_with("go") {
                            new_go_version.remove(0);
                            new_go_version.remove(0);
                        }

                        println!("Updated {} to {}", go_version, new_go_version);

                        /*
                        Clear GOROOT.
                        mkdir_all(GOROOT).
                        If GOPATH exists
                            IF GOPATH != GOROOT, clear it.
                            mkdir_all(GOPATH)
                        Untarball go into GOROOT.
                        Check/Verify go version?
                         */
                        // println!("Latest: {:?}", latest_status);
                    } else {
                        println!("You're already good to GO.");
                    }
                } else {
                    println!("Finding version failed: [{}]", relative);
                }
            } else {
                bail!("Unable to locate download link");
            }

            /*
            match status {
                cache::Status::Fetched(filename) |
                cache::Status::Cached(filename) => {
                    // Make this function the same whether or not we have a cache hit.

                    let fp = File::open(filename)?;
                    let link = find_arch_link(&go_os_arch, &fp);

                    if let Ok(relative) = link {
                        // Download link for arch located.  Make absolute URL.
                        let abs = relative_to_absolute(GO_URL, &relative).unwrap();
                        println!("URL: {}", abs);

                        let latest_version = version_from_url(&abs, &go_os_arch);
                        if let Some(latest) = latest_version {
                            println!("Version: {} [have {}]", latest, go_version);
                            if go_version != latest {
                                println!("Downloading newer version...");
                                let latest_status = cache.fetch(&abs);
                                println!("Latest: {:?}", latest_status);
                            } else {
                                println!("You're already good to GO.");
                            }
                        } else {
                            println!("Finding version failed: [{}]", abs);
                        }
                    } else {
                        bail!("Unable to locate download link");
                    }
                }
                _ => {
                    println!("Status = {:?}", status);
                }
            }
            */
        }
        Some(Commands::Info {}) => {
            println!("GOPATH      {}", go_path);
            println!("GOROOT      {}", go_root);
            println!("go ver      {}", go_version);
            println!("go_arch     {}", go_arch);
            println!("go os       {}", go_os);
            println!("go os arch: {}", go_os_arch);
        }
        None => {
            // Display help.
            let _show_help: Cli = Cli::parse_from(["", "--help"]);
        }
    }
    Ok(())
}