//! completion: generate shell completion scripts (bash, zsh, fish,
//! powershell, elvish) via clap_complete. With --installed, a dynamic
//! layer is appended: Tab then queries 'am _agents --installed' at runtime,
//! so only installed agents, aliases and groups are proposed (issue #41).

use crate::cli::Cli;
use anyhow::Result;
use clap::CommandFactory;
use clap_complete::{generate, Shell};
use std::io::Write;

pub fn run(shell: Shell, installed: bool) -> Result<i32> {
    let mut cmd = Cli::command();
    let mut buf: Vec<u8> = Vec::new();
    generate(shell, &mut cmd, "am", &mut buf);
    if installed {
        let mut text = String::from_utf8_lossy(&buf).to_string();
        match shell {
            Shell::PowerShell => {
                // Re-bind the base completer to a variable so the wrapper
                // can delegate to it.
                let marker = "Register-ArgumentCompleter -Native -CommandName 'am' -ScriptBlock {";
                if let Some(pos) = text.find(marker) {
                    text.replace_range(pos..pos + marker.len(), "$amBase = {");
                    text.push('\n');
                    text.push_str(powershell_snippet());
                }
            }
            _ => {
                text.push('\n');
                text.push_str(snippet(shell));
            }
        }
        std::io::stdout().write_all(text.as_bytes())?;
    } else {
        std::io::stdout().write_all(&buf)?;
    }
    Ok(0)
}

pub fn snippet(shell: Shell) -> &'static str {
    match shell {
        Shell::Bash => bash_snippet(),
        Shell::Zsh => zsh_snippet(),
        Shell::Fish => fish_snippet(),
        Shell::Elvish => elvish_snippet(),
        Shell::PowerShell => powershell_snippet(),
        _ => "",
    }
}

pub fn bash_snippet() -> &'static str {
    r#"# --- dynamic completion of installed agents, aliases and groups (--installed) ---
_am_installed() {
    local cur cmd
    cur="${COMP_WORDS[COMP_CWORD]}"
    cmd="${COMP_WORDS[1]}"
    case "${cmd}" in
        start|stop|restart|run|info|logs|open|install|uninstall|update|watch|favorite|unfavorite|note|tag|untag|status|sessions|stats|log)
            if [[ ${COMP_CWORD} -eq 2 ]]; then
                COMPREPLY=( $(compgen -W "$(am _agents --installed 2>/dev/null)" -- "${cur}") )
                return 0
            fi
            ;;
    esac
    _am "$@"
}
complete -F _am_installed -o nosort -o bashdefault -o default am
"#
}

pub fn zsh_snippet() -> &'static str {
    r#"# --- dynamic completion of installed agents, aliases and groups (--installed) ---
_am_installed() {
    local -a agents
    if [[ ${CURRENT} -eq 3 ]] && [[ ${words[2]} =~ ^(start|stop|restart|run|info|logs|open|install|uninstall|update|watch|favorite|unfavorite|note|tag|untag|status|sessions|stats|log)$ ]]; then
        agents=("${(@f)$(am _agents --installed 2>/dev/null)}")
        _describe -t agents 'agent' agents
        return
    fi
    _am "$@"
}
compdef _am_installed am
"#
}

pub fn fish_snippet() -> &'static str {
    r#"# --- dynamic completion of installed agents, aliases and groups (--installed) ---
complete -c am -n "__fish_seen_subcommand_from start stop restart run info logs open install uninstall update watch favorite unfavorite note tag untag status sessions stats log" -f -a "(am _agents --installed 2>/dev/null)"
"#
}

pub fn elvish_snippet() -> &'static str {
    r#"# --- dynamic completion of installed agents, aliases and groups (--installed) ---
var am-base = $edit:completion:arg-completer[am]
set edit:completion:arg-completer[am] = {|@words|
    if (and (>= (count $words) 2) (<= (count $words) 3) (has-value [start stop restart run info logs open install uninstall update watch favorite unfavorite note tag untag status sessions stats log] $words[1])) {
        put $@(am _agents --installed)
    } else {
        $am-base $@words
    }
}
"#
}

pub fn powershell_snippet() -> &'static str {
    r#"
# --- dynamic completion of installed agents, aliases and groups (--installed) ---
Register-ArgumentCompleter -Native -CommandName 'am' -ScriptBlock {
    param($wordToComplete, $commandAst, $cursorPosition)
    $tokens = $commandAst.CommandElements | ForEach-Object { $_.Extent.Text }
    $agentCommands = @('start','stop','restart','run','info','logs','open','install','uninstall','update','watch','favorite','unfavorite','note','tag','untag','status','sessions','stats','log')
    if ($tokens.Count -ge 2 -and $agentCommands -contains $tokens[1]) {
        (am _agents --installed 2>$null) | Where-Object { $_ -like "$wordToComplete*" } | ForEach-Object {
            [System.Management.Automation.CompletionResult]::new($_, $_, 'ParameterValue', $_)
        }
        return
    }
    & $amBase $wordToComplete $commandAst $cursorPosition
}
"#
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn dynamic_snippets_are_produced_for_every_shell() {
        for shell in [
            Shell::Bash,
            Shell::Zsh,
            Shell::Fish,
            Shell::Elvish,
            Shell::PowerShell,
        ] {
            let text = snippet(shell);
            assert!(text.contains("_agents --installed"), "{shell:?}");
            assert!(text.contains("favorite"), "{shell:?}");
        }
    }

    #[test]
    fn base_script_has_no_dynamic_layer() {
        let mut cmd = Cli::command();
        let mut buf: Vec<u8> = Vec::new();
        generate(Shell::Bash, &mut cmd, "am", &mut buf);
        let base = String::from_utf8(buf).unwrap();
        assert!(!base.contains("_am_installed"));
        assert!(base.contains("complete -F _am "));
    }
}