package cli

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"

	"github.com/spf13/cobra"

	"github.com/kotoyuuko/cc-switch-cli/internal/provider"
	"github.com/kotoyuuko/cc-switch-cli/internal/runner"
)

const pickerMaxRetries = 3

func newUseCmd(app *appState) *cobra.Command {
	return &cobra.Command{
		Use:   "use [name]",
		Short: "Launch claude with a provider's env",
		Args:  cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			return runUse(cmd, app, args)
		},
	}
}

func runUse(cmd *cobra.Command, app *appState, args []string) error {
	if len(app.cfg.Providers) == 0 {
		return fmt.Errorf("no providers configured; run `cc-switch add <name> ...` first")
	}

	name, err := selectProvider(app, args)
	if err != nil {
		return err
	}
	p, ok := app.cfg.Providers[name]
	if !ok {
		return fmt.Errorf("provider %q does not exist", name)
	}
	app.tracef("selected provider: %s", name)

	// Resolve claude path BEFORE we start doing any env work, so a missing
	// binary fails loud and early.
	claudePath, err := runner.ResolveClaudePath(app.cfg)
	if err != nil {
		return err
	}
	app.tracef("claude path: %s", claudePath)

	// 1. Snapshot parent env (before any cleanup or mutation).
	snapshot := provider.SnapshotEnv(os.Environ())
	// 2. Resolve env:VAR references against that snapshot.
	resolved, err := provider.ResolveEnvRefs(p, snapshot)
	if err != nil {
		return err
	}
	// 3. Compute union of all providers' env keys (cleanup set).
	union := provider.UnionEnvKeys(app.cfg.Providers)
	app.tracef("union env keys: %s", strings.Join(union, ","))
	// 4. Build the child env.
	childEnv := provider.BuildChildEnv(os.Environ(), union, resolved)
	// For trace, print the final injected keys (never values).
	if app.verbose {
		keys := make([]string, 0, len(resolved))
		for k := range resolved {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		app.tracef("injecting keys: %s", strings.Join(keys, ","))
	}

	// Pass through any extra argv after `use <name>` if support were ever
	// added; for now Args caps us at 1 arg, so no extra args flow through.
	// (cobra stores them in positional args; we already consumed args[0].)
	extraArgs := []string{}
	if len(args) > 1 {
		extraArgs = args[1:]
	}

	code, runErr := runner.Run(claudePath, childEnv, extraArgs)
	// Record whatever claude's exit code was so the CLI propagates it.
	exit := code
	app.requestedExit = &exit
	app.tracef("cleanup complete; claude exit code=%d", code)
	if runErr != nil {
		// A launch/wait failure. Surface it as the returned error while
		// still honoring the requested exit code.
		return runErr
	}
	return nil
}

// selectProvider decides which provider to run. Rules (from cli spec):
//   - if args has one name, validate and return it.
//   - if tty: interactive menu, up to pickerMaxRetries attempts.
//   - if non-tty: fall back to default_provider, else error.
func selectProvider(app *appState, args []string) (string, error) {
	if len(args) >= 1 {
		name := args[0]
		if _, ok := app.cfg.Providers[name]; !ok {
			return "", fmt.Errorf("provider %q does not exist (see `cc-switch list`)", name)
		}
		return name, nil
	}

	if !isTTY(app.stdin) {
		if app.cfg.DefaultProvider != "" {
			return app.cfg.DefaultProvider, nil
		}
		return "", fmt.Errorf(
			"non-interactive invocation requires a provider name or a configured default " +
				"(set one with `cc-switch config set default <name>`)")
	}

	return promptProvider(app)
}

// promptProvider renders the numbered list and reads user input. Empty input
// selects the default (if set). The user may type a number or a name.
func promptProvider(app *appState) (string, error) {
	names := app.cfg.SortedProviderNames()
	reader := bufio.NewReader(app.stdin)

	for attempt := 0; attempt < pickerMaxRetries; attempt++ {
		fmt.Fprintln(app.stdout, "Select provider:")
		for i, n := range names {
			marker := "  "
			if n == app.cfg.DefaultProvider {
				marker = "* "
			}
			fmt.Fprintf(app.stdout, "%s%d) %s\n", marker, i+1, n)
		}
		if app.cfg.DefaultProvider != "" {
			fmt.Fprintf(app.stdout, "> [%s] ", app.cfg.DefaultProvider)
		} else {
			fmt.Fprint(app.stdout, "> ")
		}

		line, err := reader.ReadString('\n')
		if err != nil && line == "" {
			return "", err
		}
		input := strings.TrimSpace(line)

		if input == "" {
			if app.cfg.DefaultProvider == "" {
				fmt.Fprintln(app.stderr, "no default provider configured; enter a number or name")
				continue
			}
			return app.cfg.DefaultProvider, nil
		}

		if idx, err := strconv.Atoi(input); err == nil {
			if idx >= 1 && idx <= len(names) {
				return names[idx-1], nil
			}
			fmt.Fprintf(app.stderr, "invalid selection %d\n", idx)
			continue
		}
		if _, ok := app.cfg.Providers[input]; ok {
			return input, nil
		}
		fmt.Fprintf(app.stderr, "unknown provider %q\n", input)
	}
	return "", fmt.Errorf("gave up after %d invalid selections", pickerMaxRetries)
}