package cli

import (
	"bufio"
	"fmt"
	"io"
	"strings"

	"github.com/spf13/cobra"

	"github.com/kotoyuuko/cc-switch-cli/internal/config"
	"github.com/kotoyuuko/cc-switch-cli/internal/templates"
)

func newAddCmd(app *appState) *cobra.Command {
	var (
		envFlags       []string
		description    string
		fromTemplate   string
		nonInteractive bool
	)
	cmd := &cobra.Command{
		Use:   "add <name>",
		Short: "Add a new provider",
		Args:  cobra.ExactArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			return runAdd(app, args[0], envFlags, description, fromTemplate, nonInteractive)
		},
	}
	cmd.Flags().StringArrayVar(&envFlags, "env", nil,
		"KEY=VALUE env entry (repeatable)")
	cmd.Flags().StringVar(&description, "description", "",
		"optional human-readable description")
	cmd.Flags().StringVar(&fromTemplate, "from-template", "",
		"use a built-in template as the env skeleton")
	cmd.Flags().BoolVar(&nonInteractive, "non-interactive", false,
		"never prompt; require values via --env / template defaults")
	return cmd
}

func runAdd(app *appState, name string, envFlags []string, description, fromTemplate string, nonInteractive bool) error {
	if err := config.ValidateProviderName(name); err != nil {
		return err
	}
	if _, exists := app.cfg.Providers[name]; exists {
		return fmt.Errorf("provider %q already exists (use `edit` or pick a different name)", name)
	}

	// Parse --env flags into a map up front; flags override any template seed.
	explicitEnv, err := parseEnvFlags(envFlags)
	if err != nil {
		return err
	}

	var env map[string]string

	tty := isTTY(app.stdin)

	switch {
	case fromTemplate != "":
		tpl, ok := templates.Get(fromTemplate)
		if !ok {
			return fmt.Errorf("unknown template %q; run `cc-switch templates list` to see available",
				fromTemplate)
		}
		env = make(map[string]string, len(tpl.Env))
		if nonInteractive || !tty {
			// Fill with defaults for keys the user didn't override.
			for _, e := range tpl.Env {
				if v, set := explicitEnv[e.Name]; set {
					env[e.Name] = v
					continue
				}
				env[e.Name] = e.Default
			}
			// Flags might also introduce keys not in the template.
			for k, v := range explicitEnv {
				if _, already := env[k]; !already {
					env[k] = v
				}
			}
		} else {
			env, err = runTemplateWizard(app, tpl, explicitEnv)
			if err != nil {
				return err
			}
		}

	case len(explicitEnv) > 0:
		env = explicitEnv

	default:
		// No template, no --env.
		if !tty || nonInteractive {
			return fmt.Errorf(
				"non-interactive invocation requires --env KEY=VALUE or --from-template <tpl>")
		}
		env, err = runFreeWizard(app)
		if err != nil {
			return err
		}
	}

	// Reject empty values — the spec forbids landing with a placeholder.
	for k, v := range env {
		if v == "" {
			return fmt.Errorf("env key %q has no value (after template+flags)", k)
		}
	}
	if len(env) == 0 {
		return fmt.Errorf("provider %q: env must contain at least one key", name)
	}

	p := config.Provider{Description: description, Env: env}
	if err := app.cfg.AddProvider(name, p); err != nil {
		return err
	}
	if err := app.save(); err != nil {
		return err
	}
	fmt.Fprintf(app.stdout, "added provider %q (%d env keys)\n", name, len(env))
	return nil
}

// parseEnvFlags converts --env KEY=VALUE (repeatable) to a map. KEY must be
// non-empty; VALUE may contain '=' freely.
func parseEnvFlags(flags []string) (map[string]string, error) {
	out := make(map[string]string, len(flags))
	for _, kv := range flags {
		eq := strings.IndexByte(kv, '=')
		if eq <= 0 {
			return nil, fmt.Errorf("--env %q: expected KEY=VALUE", kv)
		}
		k := kv[:eq]
		v := kv[eq+1:]
		out[k] = v
	}
	return out, nil
}

// runTemplateWizard walks the user through each template key. Values from
// explicitEnv are treated as "already provided" and skipped. Empty input
// accepts the template default if present; otherwise the user must supply
// a non-empty value.
func runTemplateWizard(app *appState, tpl templates.Template, explicit map[string]string) (map[string]string, error) {
	env := make(map[string]string, len(tpl.Env))
	reader := bufio.NewReader(app.stdin)

	fmt.Fprintf(app.stdout, "using template %q: %s\n", tpl.Name, tpl.Description)

	for _, e := range tpl.Env {
		if v, set := explicit[e.Name]; set {
			env[e.Name] = v
			fmt.Fprintf(app.stdout, "  %s: (from --env)\n", e.Name)
			continue
		}
		prompt := fmt.Sprintf("  %s", e.Name)
		if e.Hint != "" {
			prompt += fmt.Sprintf(" (%s)", e.Hint)
		}
		if e.Default != "" {
			prompt += fmt.Sprintf(" [%s]", e.Default)
		}
		prompt += ": "
		fmt.Fprint(app.stdout, prompt)

		line, err := readLine(reader)
		if err != nil {
			return nil, err
		}
		line = strings.TrimSpace(line)
		if line == "" {
			if e.Default == "" {
				return nil, fmt.Errorf("key %q requires a value", e.Name)
			}
			env[e.Name] = e.Default
		} else {
			env[e.Name] = line
		}
	}

	// Allow --env to introduce extra keys the template didn't list.
	for k, v := range explicit {
		if _, already := env[k]; !already {
			env[k] = v
		}
	}
	return env, nil
}

// runFreeWizard keeps prompting for key/value pairs until the user gives an
// empty key.
func runFreeWizard(app *appState) (map[string]string, error) {
	env := map[string]string{}
	reader := bufio.NewReader(app.stdin)

	fmt.Fprintln(app.stdout, "Enter env keys one at a time. Blank key to finish.")
	for {
		fmt.Fprint(app.stdout, "  KEY: ")
		k, err := readLine(reader)
		if err != nil {
			return nil, err
		}
		k = strings.TrimSpace(k)
		if k == "" {
			break
		}
		fmt.Fprintf(app.stdout, "  %s value: ", k)
		v, err := readLine(reader)
		if err != nil {
			return nil, err
		}
		env[k] = strings.TrimRight(v, "\r\n")
	}
	if len(env) == 0 {
		return nil, fmt.Errorf("no env keys supplied")
	}
	return env, nil
}

// readLine reads one line (without trailing newline). On EOF with no data it
// returns io.EOF so callers can distinguish end-of-stream from empty input.
func readLine(r *bufio.Reader) (string, error) {
	line, err := r.ReadString('\n')
	if len(line) == 0 && err != nil {
		return "", err
	}
	return strings.TrimRight(line, "\n"), nil
}

// silence "unused import" on io if we drop readLine later.
var _ io.Reader