import type { CommandSpec } from 'lib/commands/spec.js'

import { renderBashCompletion } from './render-bash.js'
import { renderFishCompletion } from './render-fish.js'
import { renderZshCompletion } from './render-zsh.js'

export const completionShells = ['bash', 'fish', 'zsh'] as const

export type CompletionShell = (typeof completionShells)[number]

export const isCompletionShell = (shell: unknown): shell is CompletionShell =>
  completionShells.includes(shell as CompletionShell)

const renderers: Record<CompletionShell, (spec: CommandSpec) => string> = {
  bash: renderBashCompletion,
  fish: renderFishCompletion,
  zsh: renderZshCompletion,
}

export const renderCompletion = (
  shell: CompletionShell,
  spec: CommandSpec,
): string => renderers[shell](spec)

/**
 * Render the completion loader installed by system packages. The loader is
 * embedded in the CLI and printed by `seam completion --loader <shell>`.
 *
 * The loader runs 'seam completion' the first time the shell completes a seam
 * command, so installed completions always match the CLI's current Seam API
 * schema instead of the schema packaged at release time. Each shell
 * loads its completion file on demand, so the CLI runs once per shell session
 * at first completion, never at shell startup.
 *
 * The loader degrades to no completions when the seam command is missing or
 * does not produce a completion script: a script is only evaluated when it
 * starts with the exact first line 'seam completion' generates, so nothing
 * else the CLI may print, e.g., 'Not logged in' from a version without the
 * completion command, is ever evaluated as shell code.
 */
export const renderCompletionStub = (shell: CompletionShell): string =>
  stubs[shell]

export const renderCompletionEval = (shell: CompletionShell): string => {
  const loader = `seam completion --loader ${shell} 2> /dev/null`
  return shell === 'fish' ? `${loader} | source` : `eval "$(${loader})"`
}

/**
 * First line of each generated completion script, which the loaders require
 * before evaluating one. Must match the output of {@link renderCompletion}.
 */
export const completionScriptSentinels: Record<CompletionShell, string> = {
  bash: '# bash completion for the seam command.',
  fish: '# fish completion for the seam command.',
  zsh: '#compdef seam',
}

const stubHeader = (shell: CompletionShell): string =>
  `# ${shell} completion loader for the seam command.
#
# Generated by @seamapi/cli. Loads completions from the CLI on first use, so
# they always match the CLI's current Seam API schema. Requires the seam
# command on PATH. Print the underlying script with 'seam completion ${shell}'.`

const stubs: Record<CompletionShell, string> = {
  bash: `${stubHeader('bash')}
#
# Install to /usr/share/bash-completion/completions/seam

_seam_completion_loader() {
  local script
  script="$(seam completion bash 2> /dev/null)"
  # Evaluate only a completion script, never anything else the CLI printed.
  case "$script" in
    '${completionScriptSentinels.bash}'*) eval "$script" ;;
    *) return 1 ;;
  esac
  return 124
}

if ((BASH_VERSINFO[0] > 4 || (BASH_VERSINFO[0] == 4 && BASH_VERSINFO[1] >= 1))); then
  complete -F _seam_completion_loader seam
else
  _seam_completion_loader || :
fi
`,
  fish: `${stubHeader('fish')}
#
# Install to /usr/share/fish/vendor_completions.d/seam.fish

if command --query seam
    set -l __seam_completion_script (seam completion fish 2> /dev/null | string collect)
    # Source only a completion script, never anything else the CLI printed.
    if string match --quiet '${completionScriptSentinels.fish}*' -- $__seam_completion_script
        printf '%s\\n' $__seam_completion_script | source
    end
end
`,
  zsh: `#compdef seam
${stubHeader('zsh')}
#
# Install to a directory in fpath as _seam

_seam() {
  local script
  script="$(seam completion zsh 2> /dev/null)"
  # Evaluate only a completion script, never anything else the CLI printed.
  # The script ends by dispatching on funcstack, so evaluating it while this
  # _seam runs both redefines _seam and completes the in-flight request.
  if [[ "$script" == '${completionScriptSentinels.zsh}'* ]]; then
    eval "$script"
  fi
}

if (( $+functions[compdef] )); then
  compdef _seam seam
fi

if (( \${funcstack[(I)_seam]} )); then
  _seam "$@"
fi
`,
}