//! README help-section verification and update logic.

//!

//! The README embeds the `--help` output between two HTML comment delimiters:

//!

//! ````text

//! <!-- HELP_OUTPUT_START -->

//! ```cmd

//! cssh-rs.exe --help

//! <help content>

//! ```

//! <!-- HELP_OUTPUT_END -->

//! ````

//!

//! [`check_readme_help`] fails when the embedded text differs from the live

//! output. [`update_readme_help`] rewrites the README when they differ and

//! signals the change to the caller so a pre-commit hook can abort.

use std::sync::LazyLock;

use anyhow::{bail, Context, Result};

use cssh_rs_meta::PACKAGE_NAME;

const START_MARKER: &str = "<!-- HELP_OUTPUT_START -->";

const END_MARKER: &str = "<!-- HELP_OUTPUT_END -->";

static PREAMBLE: LazyLock<String> =

    LazyLock::new(|| format!("\r\n```cmd\r\n{PACKAGE_NAME}.exe --help\r\n"));

const POSTAMBLE: &str = "\r\n```\r\n";

/// All side-effecting operations required by this module.

///

/// Implement with mocks in tests to achieve zero filesystem and process

/// side-effects.

pub trait ReadmeSystem {

    /// Run `cargo run --package cssh-rs -- --help` and return the captured output.

    ///

    /// # Errors

    ///

    /// Returns an error if the process cannot be started or exits non-zero.

    fn get_help_output(&self) -> Result<String>;

    /// Read the full contents of `README.md`.

    ///

    /// # Errors

    ///

    /// Returns an error if the file cannot be read.

    fn read_readme(&self) -> Result<String>;

    /// Write `content` to `README.md`.

    ///

    /// # Errors

    ///

    /// Returns an error if the write fails.

    fn write_readme(&self, content: &str) -> Result<()>;

}

/// Production implementation of [`ReadmeSystem`].

pub struct RealSystem;

#[cfg_attr(coverage_nightly, coverage(off))]

impl ReadmeSystem for RealSystem {

    fn get_help_output(&self) -> Result<String> {

        let output = std::process::Command::new("cargo")

            .args(["run", "--package", PACKAGE_NAME, "--", "--help"])

            .output()

            .with_context(|| {

                format!("failed to run `cargo run --package {PACKAGE_NAME} -- --help`")

            })?;

        let raw = String::from_utf8_lossy(&output.stdout).into_owned();

        Ok(raw)

    }

    fn read_readme(&self) -> Result<String> {

        std::fs::read_to_string("README.md").context("failed to read README.md")

    }

    fn write_readme(&self, content: &str) -> Result<()> {

        std::fs::write("README.md", content).context("failed to write README.md")

    }

}

/// Normalize raw `--help` output for comparison with the README section.

///

/// Replaces lines that contain only whitespace with empty lines, normalizes

/// all line endings to `\r\n`, and trims leading and trailing whitespace.

///

/// # Arguments

///

/// * `raw` - Raw output from `--help`, possibly with mixed line endings.

///

/// # Returns

///

/// Normalized string ready for comparison with the README section.

///

pub fn normalize_help_output(raw: &str) -> String {

    let normalized: Vec<&str> = raw

        .lines()

        .
map6
(|line| if line.trim().is_empty() { 
""1
 } else { 
line8
 })

        .collect();

    let joined = normalized.join("\r\n");

    joined.trim().to_owned()

}

/// Extract the help text embedded in the README between the delimiters.

///

/// # Arguments

///

/// * `readme` - Full README contents.

///

/// # Returns

///

/// The help content string (trimmed), or an error if either delimiter is missing.

///

/// # Errors

///

/// Returns an error if `<!-- HELP_OUTPUT_START -->` or `<!-- HELP_OUTPUT_END -->`

/// is absent, or if the expected preamble/postamble structure is not found.

pub fn extract_readme_help_section(readme: &str) -> Result<&str> {

    let 
start_marker_pos6
 = readme

        .find(START_MARKER)

        .context("could not find <!-- HELP_OUTPUT_START --> in README.md")
?1
;

    let 
end_marker_pos5
 = readme

        .find(END_MARKER)

        .context("could not find <!-- HELP_OUTPUT_END --> in README.md")
?1
;

    let content_start = start_marker_pos + START_MARKER.len() + PREAMBLE.len();

    let content_end = end_marker_pos - POSTAMBLE.len();

    if content_start > content_end {

        bail!("README help section delimiters are malformed or out of order");

    }

    Ok(readme[content_start..content_end].trim())

}

/// Rebuild the README with the help section replaced by `new_help`.

///

/// All content outside the delimiters and the fixed preamble/postamble is

/// preserved byte-for-byte.

///

/// # Arguments

///

/// * `readme` - Full README contents.

/// * `new_help` - Normalized help text to embed.

///

/// # Returns

///

/// New full README string.

///

/// # Errors

///

/// Returns an error if the delimiters are not found.

pub fn replace_readme_help_section(readme: &str, new_help: &str) -> Result<String> {

    let start_marker_pos = readme

        .find(START_MARKER)

        .context("could not find <!-- HELP_OUTPUT_START --> in README.md")
?0
;

    let end_marker_pos = readme

        .find(END_MARKER)

        .context("could not find <!-- HELP_OUTPUT_END --> in README.md")
?0
;

    let content_start = start_marker_pos + START_MARKER.len() + PREAMBLE.len();

    let content_end = end_marker_pos - POSTAMBLE.len();

    let before = &readme[..content_start];

    let after = &readme[content_end..];

    Ok(format!("{before}{new_help}{after}"))

}

/// Compare the live `--help` output against the README's embedded help section.

///

/// Prints a colored diff to stdout when they differ.

///

/// # Arguments

///

/// * `system` - Injected I/O provider.

///

/// # Returns

///

/// `Ok(())` if they match; an error describing the mismatch otherwise.

///

/// # Errors

///

/// Returns an error when the sections differ or when any I/O operation fails.

pub fn check_readme_help<S: ReadmeSystem>(system: &S) -> Result<()> {

    let raw_help = system.get_help_output()
?0
;

    let actual_help = normalize_help_output(&raw_help);

    let readme = system.read_readme()
?0
;

    let readme_help = extract_readme_help_section(&readme)
?0
;

    if actual_help == readme_help {

        log::info!("README.md help output is up to date.");

        return Ok(());

    }

    log::error!(

        "README.md help output is outdated!\n\

         \n\

         Differences found:\n\

         ==================\n\

         README has:\n\

         {readme_help}\n\

         \n\

         Current --help output:\n\

         {actual_help}\n\

         \n\

         ==> Run `cargo xtask update-readme-help` to fix this."

    );

    bail!("README.md help output is outdated")

}

/// Ensure the README's embedded help section matches the live `--help` output,

/// writing an updated README when they differ.

///

/// # Arguments

///

/// * `system` - Injected I/O provider.

///

/// # Returns

///

/// `Ok(true)` when the README was modified (the caller should exit with code 1

/// to abort a pre-commit hook); `Ok(false)` when already up to date.

///

/// # Errors

///

/// Returns an error when any I/O operation fails.

pub fn update_readme_help<S: ReadmeSystem>(system: &S) -> Result<bool> {

    let raw_help = system.get_help_output()
?0
;

    let actual_help = normalize_help_output(&raw_help);

    let readme = system.read_readme()
?0
;

    let readme_help = extract_readme_help_section(&readme)
?0
;

    if actual_help == readme_help {

        log::info!("README.md help section is up to date, nothing to be done.");

        return Ok(false);

    }

    log::warn!("README.md help section is outdated - fixing it.");

    let new_readme = replace_readme_help_section(&readme, &actual_help)
?0
;

    system.write_readme(&new_readme)
?0
;

    log::info!("README.md help section has been updated with current --help output.");

    Ok(true)

}

#[cfg(test)]

#[path = "tests/test_readme.rs"]

mod tests;