use std::fmt::{Display, Formatter};
use std::path::Path;
use std::process::Command;

use color_eyre::eyre::eyre;
use color_eyre::eyre::Context;
use color_eyre::eyre::Result;
use tracing::{debug, error, warn};

use crate::command::CommandExt;
use crate::error::{self, TopgradeError};
use crate::terminal::print_separator;
use crate::{execution_context::ExecutionContext, utils::require};

// A string found in the output of docker for containers that weren't found in
// the docker registry. We use this to gracefully handle and skip containers
// that cannot be pulled, likely because they don't exist in the registry in
// the first place. This happens e.g. when the user tags an image locally
// themselves or when using docker-compose.
const NONEXISTENT_REPO: &str = "repository does not exist";

/// Uniquely identifies a `Container`.
#[derive(Debug)]
struct Container {
    /// `Repository` and `Tag`
    ///
    /// format: `Repository:Tag`, e.g., `nixos/nix:latest`.
    repo_tag: String,
    /// Platform
    ///
    /// format: `OS/Architecture`, e.g., `linux/amd64`.
    platform: String,
}

impl Container {
    /// Construct a new `Container`.
    fn new(repo_tag: String, platform: String) -> Self {
        Self { repo_tag, platform }
    }
}

impl Display for Container {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        // e.g., "`fedora:latest` for `linux/amd64`"
        write!(f, "`{}` for `{}`", self.repo_tag, self.platform)
    }
}

/// Returns a Vector of all containers, with Strings in the format
/// "REGISTRY/[PATH/]CONTAINER_NAME:TAG"
fn list_containers(crt: &Path) -> Result<Vec<Container>> {
    debug!(
        "Querying '{} image ls --format \"{{{{.Repository}}}}:{{{{.Tag}}}}/{{{{.ID}}}}\"' for containers",
        crt.display()
    );
    let output = Command::new(crt)
        .args(["image", "ls", "--format", "{{.Repository}}:{{.Tag}} {{.ID}}"])
        .output_checked_with_utf8(|_| Ok(()))?;

    let mut retval = vec![];
    for line in output.stdout.lines() {
        if line.starts_with("localhost") {
            // Don't know how to update self-built containers
            debug!("Skipping self-built container '{}'", line);
            continue;
        }

        if line.contains("<none>") {
            // Bogus/dangling container or intermediate layer
            debug!("Skipping bogus container '{}'", line);
            continue;
        }

        if line.starts_with("vsc-") {
            debug!("Skipping visual studio code dev container '{}'", line);
            continue;
        }

        debug!("Using container '{}'", line);

        // line is of format: `Repository:Tag ImageID`, e.g., `nixos/nix:latest d80fea9c32b4`
        let split_res = line.split(' ').collect::<Vec<&str>>();
        assert_eq!(split_res.len(), 2);
        let (repo_tag, image_id) = (split_res[0], split_res[1]);

        debug!(
            "Querying '{} image inspect --format \"{{{{.Os}}}}/{{{{.Architecture}}}}\"' for container {}",
            crt.display(),
            image_id
        );
        let inspect_output = Command::new(crt)
            .args(["image", "inspect", image_id, "--format", "{{.Os}}/{{.Architecture}}"])
            .output_checked_with_utf8(|_| Ok(()))?;
        let mut platform = inspect_output.stdout;
        // truncate the tailing new line character
        platform.truncate(platform.len() - 1);
        assert!(platform.contains('/'));

        retval.push(Container::new(repo_tag.to_string(), platform));
    }

    Ok(retval)
}

pub fn run_containers(ctx: &ExecutionContext) -> Result<()> {
    // Prefer podman, fall back to docker if not present
    let crt = require("podman").or_else(|_| require("docker"))?;
    debug!("Using container runtime '{}'", crt.display());

    print_separator("Containers");
    let mut success = true;
    let containers = list_containers(&crt).context("Failed to list Docker containers")?;
    debug!("Containers to inspect: {:?}", containers);

    for container in containers.iter() {
        debug!("Pulling container '{}'", container);
        let args = vec![
            "pull",
            container.repo_tag.as_str(),
            "--platform",
            container.platform.as_str(),
        ];
        let mut exec = ctx.run_type().execute(&crt);

        if let Err(e) = exec.args(&args).status_checked() {
            error!("Pulling container '{}' failed: {}", container, e);

            // Find out if this is 'skippable'
            // This is necessary e.g. for docker, because unlike podman docker doesn't tell from
            // which repository a container originates (such as `docker.io`). This has the
            // practical consequence that all containers, whether self-built, created by
            // docker-compose or pulled from the docker hub, look exactly the same to us. We can
            // only find out what went wrong by manually parsing the output of the command...
            if match exec.output_checked_utf8() {
                Ok(s) => s.stdout.contains(NONEXISTENT_REPO) || s.stderr.contains(NONEXISTENT_REPO),
                Err(e) => match e.downcast_ref::<TopgradeError>() {
                    Some(TopgradeError::ProcessFailedWithOutput(_, _, stderr)) => stderr.contains(NONEXISTENT_REPO),
                    _ => false,
                },
            } {
                warn!("Skipping unknown container '{}'", container);
                continue;
            }

            success = false;
        }
    }

    if ctx.config().cleanup() {
        // Remove dangling images
        debug!("Removing dangling images");
        if let Err(e) = ctx
            .run_type()
            .execute(&crt)
            .args(["image", "prune", "-f"])
            .status_checked()
        {
            error!("Removing dangling images failed: {}", e);
            success = false;
        }
    }

    if success {
        Ok(())
    } else {
        Err(eyre!(error::StepFailed))
    }
}