use crate::complete::CompleteOptions;
use heck::ToSnakeCase;

pub fn complete_bash(opts: &CompleteOptions) -> String {
    let usage_bin = &opts.usage_bin;
    let bin = &opts.bin;
    let bin_snake = bin.to_snake_case();
    let spec_variable = if let Some(cache_key) = &opts.cache_key {
        format!("_usage_spec_{bin_snake}_{}", cache_key.to_snake_case())
    } else {
        format!("_usage_spec_{bin_snake}")
    };
    let mut out = vec![];
    let generated_comment = if let Some(source_file) = &opts.source_file {
        format!("# @generated by usage-cli from {source_file}")
    } else {
        "# @generated by usage-cli from usage spec".to_string()
    };
    out.push(generated_comment);
    // The completion body below needs `_init_completion` and
    // `__ltrim_colon_completions` from bash-completion, so it has to be loaded
    // first. Say so, and fail legibly rather than as `command not found` if it
    // isn't. usage used to be able to embed bash-completion itself; it no longer
    // does, because that meant shipping GPL-2.0-or-later text from an MIT crate.
    //
    // These are the pre-2.12 spellings, on purpose. 2.12 renamed them
    // `_comp_initialize` / `_comp_ltrim_colon_completions` and kept the old names
    // working through its compat layer, so writing the old ones supports 2.11 as
    // well as everything after it. Writing the new ones would drop Ubuntu 24.04
    // LTS, which ships 2.11 and is supported until 2029 — and did drop it, until
    // the vendored copy that hid the problem was removed.
    //
    // `_init_completion` still gets `-- "$@"`, as upstream's own completions pass
    // it: 2.12+ forwards it to `_comp_initialize`, which stores it in `comp_args`
    // for the caller, and 2.11's `getopts` stops at the `--` and ignores the rest.
    // Nothing here reads `comp_args`, but it is declared local so that setting it
    // does not reach into the global scope.
    out.push(
        "# Requires bash-completion (https://github.com/scop/bash-completion), which must be\n\
         # sourced before this script."
            .to_string(),
    );
    out.push(format!(
        r#"_{bin_snake}() {{
    if ! type -P {usage_bin} &> /dev/null; then
        echo >&2
        echo "Error: {usage_bin} CLI not found. This is required for completions to work in {bin}." >&2
        echo "See https://usage.jdx.dev for more information." >&2
        return 1
    fi
    if ! declare -F _init_completion > /dev/null 2>&1; then
        echo >&2
        echo "Error: bash-completion is required for {bin} completions but was not loaded." >&2
        echo "Install it from your package manager and source it before this script." >&2
        return 1
    fi"#));

    // The cache filename is version-keyed and the cache dir is now persistent
    // (unlike the reboot-cleared temp dir), so old versions would accumulate
    // forever. On a cache miss, reap this bin's spec files not regenerated in
    // the last 30 days. Age-based (not "delete all other versions") so that
    // running two versions of the same tool concurrently doesn't thrash — each
    // live version's spec stays recent and survives.
    let prune_stale = format!(
        r#"find "$spec_dir" -maxdepth 1 -name 'usage__usage_spec_{bin_snake}_*.spec' -type f -mtime +30 -delete 2>/dev/null"#
    );

    // Build logic to write spec directly to file without storing in shell variables
    let file_write_logic = if let Some(usage_cmd) = &opts.usage_cmd {
        if opts.cache_key.is_some() {
            format!(
                r#"if [[ ! -f "$spec_file" ]]; then
        {prune_stale}
        {usage_cmd} >| "$spec_file"
    fi"#
            )
        } else {
            format!(r#"{usage_cmd} >| "$spec_file""#)
        }
    } else if let Some(spec) = &opts.spec {
        let heredoc = format!(
            r#"cat >| "$spec_file" <<'__USAGE_EOF__'
{spec}
__USAGE_EOF__"#,
            spec = spec.to_string().trim()
        );
        if opts.cache_key.is_some() {
            format!(
                r#"if [[ ! -f "$spec_file" ]]; then
    {prune_stale}
    {heredoc}
fi"#
            )
        } else {
            heredoc.to_string()
        }
    } else {
        String::new()
    };

    out.push(format!(
        r#"
	local cur prev words cword comp_args
    _init_completion -n : -- "$@" || return
    local spec_dir="${{XDG_CACHE_HOME:-$HOME/.cache}}/usage"
    [[ -d "$spec_dir" ]] || mkdir -p -m 700 "$spec_dir"
    local spec_file="$spec_dir/usage_{spec_variable}.spec"
    {file_write_logic}
    # shellcheck disable=SC2207
	COMPREPLY=($(compgen -W "$(command {usage_bin} complete-word --shell bash -f "$spec_file" --cword="$cword" -- "${{words[@]}}")" -- "$cur"))
	__ltrim_colon_completions "$cur"
    # shellcheck disable=SC2181
    if [[ $? -ne 0 ]]; then
        unset COMPREPLY
    fi
    return 0
}}

if [[ "${{BASH_VERSINFO[0]}}" -eq 4 && "${{BASH_VERSINFO[1]}}" -ge 4 || "${{BASH_VERSINFO[0]}}" -gt 4 ]]; then
    shopt -u hostcomplete && complete -o nospace -o bashdefault -o nosort -F _{bin_snake} {bin}
else
    shopt -u hostcomplete && complete -o nospace -o bashdefault -F _{bin_snake} {bin}
fi
# vim: noet ci pi sts=0 sw=4 ts=4 ft=sh
"#
    ));

    out.join("\n")
}

/// Generates a bash "init" script that wires up tab-completion for any command
/// on `$PATH` whose first line is a `usage` shebang. The user sources this once
/// from their shell rc; per-script `usage g completion bash <bin> -f <script>`
/// generation is no longer required.
///
/// Mechanism: registers a `complete -D` default handler. On `<Tab>`, the handler
/// resolves the command path, peeks the first line, and if it looks like a
/// `usage` shebang, dispatches to `usage complete-word`. Otherwise it chains to
/// `_completion_loader` (bash-completion's dynamic loader) when present.
pub fn complete_bash_init(usage_bin: &str) -> String {
    format!(
        r##"# @generated by usage-cli — auto-completion for usage shebang scripts
# Source this file from your bashrc to enable <Tab> completion for any command
# on $PATH whose first line is a `usage` shebang.
#
# Sourcing order: this script registers a `complete -D` default handler. Bash
# only allows one such handler — whichever script registers last wins. Source
# this AFTER bash-completion (e.g. `/etc/bash_completion` or
# `/usr/share/bash-completion/bash_completion`) so that bash-completion's own
# default handler is captured below and chained to for non-usage commands.

# Capture any pre-existing `complete -D` handler so we can chain to it for
# commands that aren't usage shebang scripts (e.g. bash-completion's loader).
# `complete -p -D` exits non-zero if no -D handler is set; tolerate that under
# `set -e`.
_usage_chained_default_complete=""
{{
    _usage_existing_d="$(complete -p -D 2>/dev/null || true)"
    if [[ "$_usage_existing_d" =~ -F[[:space:]]+([^[:space:]]+) ]]; then
        _usage_chained_default_complete="${{BASH_REMATCH[1]}}"
    fi
    unset _usage_existing_d
}}

_usage_default_complete() {{
    local cmd="${{COMP_WORDS[0]}}"
    local cmdpath
    if [[ "$cmd" == */* ]]; then
        cmdpath="$cmd"
    else
        cmdpath="$(type -P "$cmd" 2>/dev/null)"
    fi

    if [[ -n "$cmdpath" && -f "$cmdpath" ]]; then
        local first
        if IFS= read -r first < "$cmdpath" 2>/dev/null && [[ "$first" == "#!"*"usage"* ]]; then
            if type -P {usage_bin} &> /dev/null; then
                local IFS=$'\n'
                # shellcheck disable=SC2207
                COMPREPLY=( $(command {usage_bin} complete-word --shell bash -f "$cmdpath" --cword="$COMP_CWORD" -- "${{COMP_WORDS[@]}}") )
                return 0
            fi
        fi
    fi

    # Chain to whatever default handler was registered before us, if any.
    if [[ -n "$_usage_chained_default_complete" ]] \
        && [[ "$_usage_chained_default_complete" != "_usage_default_complete" ]] \
        && declare -F "$_usage_chained_default_complete" >/dev/null 2>&1; then
        "$_usage_chained_default_complete" "$@"
        return $?
    fi
    if declare -F _completion_loader >/dev/null 2>&1; then
        _completion_loader "$@"
        return $?
    fi
    return 1
}}

complete -D -F _usage_default_complete -o bashdefault -o default
# vim: noet ci pi sts=0 sw=4 ts=4 ft=sh
"##
    )
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::test::SPEC_KITCHEN_SINK;
    use insta::assert_snapshot;

    #[test]
    fn test_complete_bash_init() {
        assert_snapshot!(complete_bash_init("usage"));
    }

    #[test]
    fn test_complete_bash() {
        assert_snapshot!(complete_bash(&CompleteOptions {
            usage_bin: "usage".to_string(),
            shell: "bash".to_string(),
            bin: "mycli".to_string(),
            cache_key: None,
            spec: None,
            usage_cmd: Some("mycli complete --usage".to_string()),
            source_file: None,
        }));
        assert_snapshot!(complete_bash(&CompleteOptions {
            usage_bin: "usage".to_string(),
            shell: "bash".to_string(),
            bin: "mycli".to_string(),
            cache_key: Some("1.2.3".to_string()),
            spec: None,
            usage_cmd: Some("mycli complete --usage".to_string()),
            source_file: None,
        }));
        assert_snapshot!(complete_bash(&CompleteOptions {
            usage_bin: "usage".to_string(),
            shell: "bash".to_string(),
            bin: "mycli".to_string(),
            cache_key: None,
            spec: Some(SPEC_KITCHEN_SINK.clone()),
            usage_cmd: None,
            source_file: None,
        }));
    }
}
