use std::{path::PathBuf, str::FromStr};

use anyhow::Context;
use clap::{Arg, ArgMatches, Command};

use crate::{cli::CuddleCli, model::CuddleVariable};

const DESTINATION: &str = "destination is the output path of the template once done, but default .tmpl is stripped and the normal file extension is used. this can be overwritten if a file path is entered instead. I.e. (/some/file/name.txt)";
const TEMPLATE_FILE: &str = "template-file is the input file path of the .tmpl file (or inferred) that you would like to render";

pub fn build_command(root_cmd: Command) -> Command {
    root_cmd.subcommand(
        Command::new("render_template")
            .about("renders a jinja compatible template")
            .args(&[
                Arg::new("template-file")
                    .alias("template")
                    .short('t')
                    .long("template-file")
                    .required(true)
                    .action(clap::ArgAction::Set)
                    .long_help(TEMPLATE_FILE),
                Arg::new("destination")
                    .alias("dest")
                    .short('d')
                    .long("destination")
                    .required(true)
                    .action(clap::ArgAction::Set)
                    .long_help(DESTINATION),
                Arg::new("extra-var")
                    .long("extra-var")
                    .required(false)
                    .action(clap::ArgAction::Append),
            ]),
    )
}

pub struct RenderTemplateCommand {
    variables: Vec<CuddleVariable>,
    template_file: PathBuf,
    destination: PathBuf,
}

impl RenderTemplateCommand {
    pub fn from_matches(matches: &ArgMatches, cli: CuddleCli) -> anyhow::Result<Self> {
        let template_file = matches
            .get_one::<String>("template-file")
            .ok_or(anyhow::anyhow!("template-file was not found"))
            .and_then(get_path_buf_and_check_exists)?;

        let destination = matches
            .get_one::<String>("destination")
            .ok_or(anyhow::anyhow!("destination was not found"))
            .and_then(get_path_buf_and_check_dir_exists)
            .and_then(RenderTemplateCommand::transform_extension)
            .context("failed to access dest directory")?;

        let mut extra_vars: Vec<CuddleVariable> =
            if let Some(extra_vars) = matches.get_many::<String>("extra-var") {
                let mut vars = Vec::with_capacity(extra_vars.len());
                for var in extra_vars.into_iter() {
                    let parts: Vec<&str> = var.split('=').collect();
                    if parts.len() != 2 {
                        return Err(anyhow::anyhow!("extra-var: is not set correctly: {}", var));
                    }

                    vars.push(CuddleVariable::new(parts[0], parts[1]));
                }
                vars
            } else {
                vec![]
            };

        extra_vars.append(&mut cli.variables.clone());

        Ok(Self {
            variables: extra_vars,
            template_file,
            destination,
        })
    }

    pub fn execute(self) -> anyhow::Result<()> {
        // Prepare context
        let mut context = tera::Context::new();
        for var in self.variables {
            context.insert(var.name.to_lowercase().replace([' ', '-'], "_"), &var.value)
        }

        // Load source template
        let source = std::fs::read_to_string(self.template_file)?;

        let output = tera::Tera::one_off(source.as_str(), &context, false)?;

        if let Some(parent) = self.destination.parent() {
            std::fs::create_dir_all(parent)?;
        }

        // Put template in final destination
        std::fs::write(&self.destination, output).context(format!(
            "failed to write to destination: {}",
            &self.destination.display(),
        ))?;

        log::info!(
            "finished writing template to: {}",
            &self.destination.to_string_lossy()
        );

        Ok(())
    }

    fn transform_extension(template_path: PathBuf) -> anyhow::Result<PathBuf> {
        if template_path.is_file() {
            let ext = template_path.extension().ok_or(anyhow::anyhow!(
                "destination path does not have an extension"
            ))?;
            if ext.to_string_lossy().ends_with("tmpl") {
                let template_dest = template_path
                    .to_str()
                    .and_then(|s| s.strip_suffix(".tmpl"))
                    .ok_or(anyhow::anyhow!("string does not end in .tmpl"))?;

                return PathBuf::from_str(template_dest).map_err(|e| anyhow::anyhow!(e));
            }
        }

        Ok(template_path)
    }
}

fn get_path_buf_and_check_exists(raw_path: impl Into<String>) -> anyhow::Result<PathBuf> {
    match PathBuf::from_str(&raw_path.into()) {
        Ok(pb) => {
            if pb.exists() {
                Ok(pb)
            } else {
                Err(anyhow::anyhow!(
                    "path: {}, could not be found",
                    pb.to_string_lossy()
                ))
            }
        }
        Err(e) => Err(anyhow::anyhow!(e)),
    }
}

fn get_path_buf_and_check_dir_exists(raw_path: impl Into<String>) -> anyhow::Result<PathBuf> {
    match PathBuf::from_str(&raw_path.into()) {
        Ok(pb) => Ok(pb),
        Err(e) => Err(anyhow::anyhow!(e)),
    }
}