package main

import (
	"flag"
	"fmt"
	"io"

	"textmachine/backend/internal/pipeline"
)

// invocation.go: CLI argument parsing, extracted into a pure function (package №4 —
// tmctl had 0 tests for the contract invariants: bad-flag→exit 1, not 2;
// the redrive selector; validation order). The flag/error-text contract is FROZEN
// (D12/D15.3) — this function merely relocates it to a testable place.

// invocation is one parsed tmctl command line.
type invocation struct {
	cmd         string
	cfgPath     string
	seedPath    string // seed-lint: the glossary seed YAML to validate (no --config)
	resnapshot  bool
	asJSON      bool
	asPlaintext bool
	asPairs     bool // export: include the source column (--pairs) for the DC1/DC2 FP-measure
	sel         pipeline.RedriveSelector
}

// parseInvocation parses os.Args[1:] into an invocation. flagOut receives the
// stdlib's flag diagnostics ("flag provided but not defined" + usage) — main
// passes os.Stderr, tests a buffer; the bytes and their destination are part of
// the frozen contract.
//
// Deliberately preserved quirks (changing them = changing the contract):
//   - the command NAME is not validated here — `tmctl bogus --config x` reaches
//     the dispatch switch (after dotenv/ctx setup) and errors there, while
//     `tmctl bogus` without --config errors "--config book.yaml is required";
//   - ContinueOnError, NOT ExitOnError: the stdlib's ExitOnError would call
//     os.Exit(2) on a bad flag and would COLLAPSE onto exit code 2
//     (completed-with-flags); returning an error routes the bad flag into
//     main()'s default branch → exit 1, leaving 2 exclusive to flagged chunks.
func parseInvocation(args []string, flagOut io.Writer) (invocation, error) {
	if len(args) < 1 {
		return invocation{}, fmt.Errorf("usage: tmctl <translate|report|status|export|redrive> --config book.yaml")
	}
	cmd, rest := args[0], args[1:]

	fs := flag.NewFlagSet(cmd, flag.ContinueOnError)
	fs.SetOutput(flagOut)
	cfgPath := fs.String("config", "", "path to book.yaml")
	resnapshot := fs.Bool("resnapshot", false, "re-pin existing jobs to the current config snapshot (re-translates already-paid chunks — explicit consent)")
	asJSON := fs.Bool("json", false, "status: emit the projection as JSON (stable disposition/flag_reason enums) for CI/IDE")
	asPlaintext := fs.Bool("plaintext", false, "export: emit the concatenated human text instead of the default stable JSON")
	asPairs := fs.Bool("pairs", false, "export: include the source text per chunk (src↔target column for the DC1/DC2 FP-measure, WS5)")
	chapter := fs.Int("chapter", -1, "redrive: restrict to this chapter (default: any)")
	chunk := fs.Int("chunk", -1, "redrive: restrict to this chunk index within the chapter (default: any)")
	reason := fs.String("reason", "", "redrive: restrict to this flag_reason (default: any)")
	dryRun := fs.Bool("dry-run", false, "redrive: report what would be re-attacked without touching anything")
	seed := fs.String("seed", "", "seed-lint: path to the glossary seed YAML to validate ($0, no --config)")
	if err := fs.Parse(rest); err != nil {
		return invocation{}, err
	}
	// seed-lint validates a standalone seed YAML — it takes --seed, not --config (no book/store/keys).
	if cmd == "seed-lint" {
		if *seed == "" {
			return invocation{}, fmt.Errorf("--seed <glossary.yaml> is required for seed-lint")
		}
		return invocation{cmd: cmd, seedPath: *seed}, nil
	}
	if *cfgPath == "" {
		return invocation{}, fmt.Errorf("--config book.yaml is required")
	}
	return invocation{
		cmd: cmd, cfgPath: *cfgPath, resnapshot: *resnapshot, asJSON: *asJSON, asPlaintext: *asPlaintext, asPairs: *asPairs,
		sel: pipeline.RedriveSelector{
			Chapter: *chapter, ChunkIdx: *chunk, Reason: *reason, DryRun: *dryRun,
		},
	}, nil
}