use std::borrow::Cow;
use std::path::{Path, PathBuf};

use miette::{IntoDiagnostic, Result, WrapErr};
use tokio::io::AsyncWriteExt;

use crate::Context;

/// A sequential pipeline of [`Step`]s.
#[derive(Debug, Clone)]
pub struct Pipeline<'a> {
    name: &'a str,
    steps: Vec<Step<'a>>,
}

impl<'a> Pipeline<'a> {
    #[inline(always)]
    pub fn new(name: &'a str, steps: impl Into<Vec<Step<'a>>>) -> Self {
        Self {
            name,
            steps: steps.into(),
        }
    }

    pub async fn invoke(&self, ctx: &Context) -> Result<()> {
        println!("Invoking {}...", self.name);

        for step in self.steps.iter() {
            step.invoke(ctx).await?;
        }

        Ok(())
    }
}

#[derive(Debug, Clone)]
pub enum Step<'a> {
    DownloadFile {
        /// Remote resourcee to download from.
        res: RemoteResource<'a>,

        /// Path to save the downloaded file to.
        file: Cow<'a, Path>,
    },

    /// Extracts the file using the `tar` binary that ships with Windows.
    ExtractFile {
        file: Cow<'a, Path>,
        dest: Cow<'a, Path>,
    },

    ExecuteCommand {
        /// Path to the executable file.
        file: Cow<'a, Path>,

        args: &'a [&'a str],
    },

    CreateShortcut {
        /// Target of the shortcut (i.e. what is points to).
        target: ShortcutTarget<'a>,

        /// Path of the created shortcut file.
        file: Cow<'a, Path>,
    },
}

impl<'a> Step<'a> {
    pub async fn invoke(&self, ctx: &Context) -> Result<()> {
        match self {
            Self::DownloadFile { res, file } => {
                if file.exists() {
                    println!(
                        "File {file} already downloaded.",
                        file = file.to_str().unwrap_or("<NON UTF-8>")
                    );
                } else {
                    println!(
                        "Downloading file {file} from {res:?}...",
                        file = file.to_str().unwrap_or("<NON UTF-8>")
                    );
                    const FETCH_FILE_ERROR_MSG: &'static str =
                        "Fetching the remote resource failed.";
                    const WRITE_FILE_ERROR_MSG: &'static str =
                        "Writing the remote resource to disk failed.";
                    let url = match res {
                        RemoteResource::Url(url) => url::Url::parse(url)
                            .into_diagnostic()
                            .wrap_err("Invalid url for download step.")?,
                        RemoteResource::GitHubArtifact { repo, pattern } => {
                            let mut release = fetch_latest_release(&ctx.reqwest, repo).await?;
                            let pattern = ramhorns::Template::new(*pattern)
                                .into_diagnostic()
                                .wrap_err(
                                    "Invalid pattern for artifact matching in download step.",
                                )?;
                            release.meta.tag_name_strip_prefix = release
                                .meta
                                .tag_name
                                .strip_prefix('v')
                                .unwrap_or(&release.meta.tag_name);
                            let asset_name = pattern.render(&release.meta);
                            let artifact = release.assets.into_iter().filter(move |asset| asset.name == asset_name).next().ok_or_else(|| miette!("No artifact of the latest release matched the pattern in download step."))?;
                            url::Url::parse(&artifact.browser_download_url)
                                .into_diagnostic()
                                .wrap_err(
                                    "Invalid url returned by GitHub for latest release artifact.",
                                )?
                        }
                    };
                    let mut resp = ctx
                        .reqwest
                        .get(url)
                        .send()
                        .await
                        .into_diagnostic()
                        .wrap_err(FETCH_FILE_ERROR_MSG)?;
                    let _content_length = resp.content_length();
                    mkdir_all(file.parent().ok_or_else(|| {
                        miette!("Destination file for download step has no parent.")
                    })?)
                    .await?;
                    let mut writer = tokio::io::BufWriter::new(
                        tokio::fs::File::create(file.as_os_str())
                            .await
                            .into_diagnostic()
                            .wrap_err(WRITE_FILE_ERROR_MSG)?,
                    );
                    while let Some(mut chunk) = resp
                        .chunk()
                        .await
                        .into_diagnostic()
                        .wrap_err(FETCH_FILE_ERROR_MSG)?
                    {
                        writer
                            .write_all_buf(&mut chunk)
                            .await
                            .into_diagnostic()
                            .wrap_err(WRITE_FILE_ERROR_MSG)?;
                    }
                    writer
                        .flush()
                        .await
                        .into_diagnostic()
                        .wrap_err(WRITE_FILE_ERROR_MSG)?;
                }
            }
            Self::ExtractFile { file, dest } => {
                println!(
                    "Extracting {file} to {dest}...",
                    file = file.to_str().unwrap_or("<NON UTF-8>"),
                    dest = dest.to_str().unwrap_or("<NON UTF-8>")
                );
                const EXTRACT_FILE_ERROR_MSG: &'static str = "Extracting file failed.";
                mkdir_all(&dest).await.wrap_err(EXTRACT_FILE_ERROR_MSG)?;
                let dest = tokio::fs::canonicalize(&dest)
                    .await
                    .into_diagnostic()
                    .wrap_err(EXTRACT_FILE_ERROR_MSG)?;
                let status = tokio::process::Command::new("tar")
                    .arg("-xf")
                    .arg(file.as_os_str())
                    .current_dir(dest)
                    .stdout(std::process::Stdio::inherit())
                    .stderr(std::process::Stdio::inherit())
                    .status()
                    .await
                    .into_diagnostic()
                    .wrap_err(EXTRACT_FILE_ERROR_MSG)?;
                ensure!(status.success(), EXTRACT_FILE_ERROR_MSG);
            }
            Self::ExecuteCommand { file, args } => {
                println!(
                    "Executing command `{file} {args}`...",
                    file = file.to_str().unwrap_or("<NON UTF-8>"),
                    args = args.into_iter().map(|s| *s).collect::<String>(),
                );
                const EXECUTE_COMMAND_ERROR_MSG: &'static str = "Executing command failed.";
                let status = tokio::process::Command::new(file.as_os_str())
                    .args(*args)
                    .stdout(std::process::Stdio::inherit())
                    .stderr(std::process::Stdio::inherit())
                    .status()
                    .await
                    .into_diagnostic()
                    .wrap_err(EXECUTE_COMMAND_ERROR_MSG)?;
                ensure!(status.success(), EXECUTE_COMMAND_ERROR_MSG);
            }
            Self::CreateShortcut { target, file } => {
                println!(
                    "Creating shortcut to {target:?} at {file}...",
                    file = file.to_str().unwrap_or("<NON UTF-8>")
                );
                const CREATE_SHORTCUT_ERROR_MSG: &'static str = "Creating shortcut failed.";
                mkdir_all(
                    file.parent().ok_or_else(|| {
                        miette!("Destination file for shortcut step has no parent.")
                    })?,
                )
                .await?;
                let status = match target {
                    ShortcutTarget::Path { path } => {
                        tokio::process::Command::new("powershell")
                            .arg("-Command")
                            .arg(format!(r#"$shell = New-Object -ComObject WScript.Shell; $shortcut = $shell.CreateShortcut({file:?}); $shortcut.TargetPath = {path:?}; $shortcut.Save()"#))
                            .stdout(std::process::Stdio::inherit())
                            .stderr(std::process::Stdio::inherit())
                            .status()
                            .await
                            .into_diagnostic()
                            .wrap_err(CREATE_SHORTCUT_ERROR_MSG)?
                    }
                    ShortcutTarget::Executable { file: exec_file, args } => {
                        use std::fmt::Write;
                        tokio::process::Command::new("powershell")
                            .arg("-Command")
                            .arg(format!(r#"$shell = New-Object -ComObject WScript.Shell; $shortcut = $shell.CreateShortcut({file:?}); $shortcut.TargetPath = {exec_file:?}; $shortcut.Arguments = {args:?}; $shortcut.Save()"#))
                            .stdout(std::process::Stdio::inherit())
                            .stderr(std::process::Stdio::inherit())
                            .status()
                            .await
                            .into_diagnostic()
                            .wrap_err(CREATE_SHORTCUT_ERROR_MSG)?
                    }
                };
                ensure!(status.success(), CREATE_SHORTCUT_ERROR_MSG);
            }
        }
        println!("-> Done.");

        Ok(())
    }
}

#[derive(Debug, Clone, Copy)]
pub enum RemoteResource<'a> {
    // I'm not using url::Url here because it makes it impossible to make this const.
    Url(&'a str),

    GitHubArtifact {
        /// In the form `org/repo`
        repo: &'a str,

        /// Artifact name pattern.
        ///
        /// Any of the fields in [`GitHubReleaseMeta`] may be injected via handlebar syntax:
        /// `{{field_name}}`.
        /// with `v` prefix stripped if present.
        pattern: &'a str,
    },
}

#[derive(Debug, Clone)]
pub enum ShortcutTarget<'a> {
    /// An executable shortcut.
    Executable {
        /// The executable the shortcut should open.
        file: Cow<'a, Path>,

        /// Arguments to the executable.
        args: &'a str,
    },

    /// A file or folder shortcut. Please use [`Self::Executable`] for shortcuts to binaries.
    Path { path: Cow<'a, Path> },
}

#[derive(Debug, Clone, Serialize, Deserialize)]
struct GitHubRelease<'a> {
    #[serde(flatten)]
    meta: GitHubReleaseMeta<'a>,
    //reactions: todo!(),
    assets: Vec<GitHubReleaseAsset>,
}

#[derive(Debug, Clone, Serialize, Deserialize, ramhorns::Content)]
struct GitHubReleaseMeta<'a> {
    url: String,
    assets_url: String,
    upload_url: String,
    html_url: String,
    id: u64,
    //author: todo!(),
    node_id: String,
    tag_name: String,
    #[serde(skip_deserializing, default = "empty_str")]
    tag_name_strip_prefix: &'a str,
    target_commitish: String,
    name: String,
    draft: bool,
    prerelease: bool,
    created_at: String,
    published_at: String,
    tarball_url: String,
    zipball_url: String,
    body: String,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
struct GitHubReleaseAsset {
    url: String,
    id: u64,
    node_id: String,
    name: String,
    label: Option<String>,
    //uploader: todo!(),
    content_type: String,
    state: String,
    size: u64,
    download_count: u64,
    created_at: String,
    updated_at: String,
    browser_download_url: String,
}

#[inline(always)]
const fn empty_str<'a>() -> &'a str {
    ""
}

async fn mkdir_all(path: impl AsRef<Path>) -> Result<()> {
    tokio::fs::DirBuilder::new()
        .recursive(true)
        .create(path)
        .await
        .into_diagnostic()
        .wrap_err("Creating directory and any missing parents failed.")
}

async fn fetch_latest_release<'a, 'b>(
    reqwest: &'b reqwest::Client,
    repo: &'b str,
) -> Result<GitHubRelease<'a>> {
    const FETCH_META_ERROR_MSG: &'static str =
        "Fetching the latest release metadata from GitHub failed.";
    let url = url::Url::parse(&format!(
        "https://api.github.com/repos/{repo}/releases/latest"
    ))
    .into_diagnostic()
    .wrap_err("Invalid GitHub repo for download step.")?;
    let mut resp = reqwest
        .get(url)
        .send()
        .await
        .into_diagnostic()
        .wrap_err(FETCH_META_ERROR_MSG)?;
    let body = resp
        .text()
        .await
        .into_diagnostic()
        .wrap_err(FETCH_META_ERROR_MSG)?;
    let release: GitHubRelease = serde_json::from_str(&body)
        .into_diagnostic()
        .wrap_err_with(|| format!("{}: {}", FETCH_META_ERROR_MSG, body))?;
    Ok(release)
}

#[cfg(test)]
mod tests {
    #[test]
    fn decode_latest_release() {
        tokio::runtime::Builder::new_current_thread()
            .enable_io()
            .build()
            .unwrap()
            .block_on(async move {
                let body = super::fetch_latest_release(
                    &reqwest::Client::new(),
                    "notepad-plus-plus/notepad-plus-plus",
                )
                .await
                .unwrap();
                assert_eq!(body.meta.draft, false);
            });
    }
}