package config_test

import (
	"bytes"
	"errors"
	"flag"
	"io"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"kode.naiv.no/olemd/forgejo-mcp-broker/internal/config"
)

// envVars enumerates every environment variable read by the config package.
// Tests clear all of these to isolate from the ambient shell environment.
var envVars = []string{
	"FJMCP_BROKER_PUBLIC_URL",
	"FJMCP_BROKER_LISTEN",
	"FORGEJO_URL",
	"FORGEJO_OAUTH_CLIENT_ID",
	"FORGEJO_OAUTH_CLIENT_SECRET",
	"FORGEJO_OAUTH_SCOPES",
	"FJMCP_BROKER_MCP_BINARY",
	"FJMCP_BROKER_STORE",
	"FJMCP_BROKER_MAX_SESSIONS",
	"FJMCP_BROKER_IDLE_TIMEOUT",
	"FJMCP_BROKER_DEBUG",
}

// clearEnv wipes every known env var for the test's lifetime. Setting to ""
// is sufficient because the config treats empty values as unset.
func clearEnv(t *testing.T) {
	t.Helper()
	for _, k := range envVars {
		t.Setenv(k, "")
	}
}

// validBaseArgs returns the minimum required flag set, plus a writable
// store path pointing inside a per-test TempDir.
func validBaseArgs(t *testing.T) []string {
	t.Helper()
	storePath := filepath.Join(t.TempDir(), "broker.db")
	return []string{
		"--public-url", "https://mcp.example.com",
		"--forgejo-url", "https://forgejo.example.com",
		"--forgejo-oauth-client-id", "client-id",
		"--forgejo-oauth-client-secret", "client-secret",
		"--store-path", storePath,
	}
}

func TestLoad_HappyPath_Defaults(t *testing.T) {
	clearEnv(t)
	cfg, err := config.Load(validBaseArgs(t), io.Discard)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if cfg.Listen != config.DefaultListen {
		t.Errorf("Listen = %q, want %q", cfg.Listen, config.DefaultListen)
	}
	if cfg.ForgejoOAuthScopes != config.DefaultForgejoOAuthScopes {
		t.Errorf("ForgejoOAuthScopes = %q, want %q", cfg.ForgejoOAuthScopes, config.DefaultForgejoOAuthScopes)
	}
	if cfg.ForgejoMCPBinary != config.DefaultForgejoMCPBinary {
		t.Errorf("ForgejoMCPBinary = %q, want %q", cfg.ForgejoMCPBinary, config.DefaultForgejoMCPBinary)
	}
	if cfg.MaxSessions != config.DefaultMaxSessions {
		t.Errorf("MaxSessions = %d, want %d", cfg.MaxSessions, config.DefaultMaxSessions)
	}
	if cfg.SessionIdleTimeout != config.DefaultSessionIdleTimeout {
		t.Errorf("SessionIdleTimeout = %s, want %s", cfg.SessionIdleTimeout, config.DefaultSessionIdleTimeout)
	}
	if cfg.Debug {
		t.Error("Debug = true, want false by default")
	}
}

func TestLoad_Env_PopulatesAllFields(t *testing.T) {
	clearEnv(t)
	storePath := filepath.Join(t.TempDir(), "broker.db")

	t.Setenv("FJMCP_BROKER_PUBLIC_URL", "https://mcp.example.com")
	t.Setenv("FJMCP_BROKER_LISTEN", ":9090")
	t.Setenv("FORGEJO_URL", "https://forgejo.example.com")
	t.Setenv("FORGEJO_OAUTH_CLIENT_ID", "envcid")
	t.Setenv("FORGEJO_OAUTH_CLIENT_SECRET", "envcs")
	t.Setenv("FORGEJO_OAUTH_SCOPES", "read:user")
	t.Setenv("FJMCP_BROKER_MCP_BINARY", "/opt/forgejo-mcp")
	t.Setenv("FJMCP_BROKER_STORE", storePath)
	t.Setenv("FJMCP_BROKER_MAX_SESSIONS", "42")
	t.Setenv("FJMCP_BROKER_IDLE_TIMEOUT", "5m")
	t.Setenv("FJMCP_BROKER_DEBUG", "true")

	cfg, err := config.Load(nil, io.Discard)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	want := &config.Config{
		PublicURL:                "https://mcp.example.com",
		Listen:                   ":9090",
		ForgejoURL:               "https://forgejo.example.com",
		ForgejoOAuthClientID:     "envcid",
		ForgejoOAuthClientSecret: "envcs",
		ForgejoOAuthScopes:       "read:user",
		ForgejoMCPBinary:         "/opt/forgejo-mcp",
		StorePath:                storePath,
		MaxSessions:              42,
		SessionIdleTimeout:       5 * time.Minute,
		Debug:                    true,
	}
	if *cfg != *want {
		t.Errorf("cfg mismatch\n got: %+v\nwant: %+v", *cfg, *want)
	}
}

func TestLoad_FlagBeatsEnv(t *testing.T) {
	clearEnv(t)
	storePath := filepath.Join(t.TempDir(), "broker.db")

	t.Setenv("FJMCP_BROKER_PUBLIC_URL", "https://env.example.com")
	t.Setenv("FORGEJO_URL", "https://env-forgejo.example.com")
	t.Setenv("FORGEJO_OAUTH_CLIENT_ID", "env-cid")
	t.Setenv("FORGEJO_OAUTH_CLIENT_SECRET", "env-cs")
	t.Setenv("FJMCP_BROKER_STORE", storePath)
	t.Setenv("FJMCP_BROKER_MAX_SESSIONS", "10")

	cfg, err := config.Load([]string{
		"--public-url", "https://flag.example.com",
		"--max-sessions", "77",
	}, io.Discard)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if cfg.PublicURL != "https://flag.example.com" {
		t.Errorf("PublicURL = %q, want flag value", cfg.PublicURL)
	}
	if cfg.MaxSessions != 77 {
		t.Errorf("MaxSessions = %d, want 77", cfg.MaxSessions)
	}
	// Unoverridden fields should still come from env:
	if cfg.ForgejoOAuthClientID != "env-cid" {
		t.Errorf("ForgejoOAuthClientID = %q, want env-cid", cfg.ForgejoOAuthClientID)
	}
}

func TestLoad_EmptyEnvTreatedAsUnset(t *testing.T) {
	// An exported-but-empty variable must not clobber the default. This matches
	// the shell idiom where `export FOO=` is effectively a reset.
	clearEnv(t)
	t.Setenv("FJMCP_BROKER_LISTEN", "") // empty => use default
	cfg, err := config.Load(validBaseArgs(t), io.Discard)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if cfg.Listen != config.DefaultListen {
		t.Errorf("Listen = %q, want default %q", cfg.Listen, config.DefaultListen)
	}
}

func TestLoad_MissingRequired_ListsAllFields(t *testing.T) {
	clearEnv(t)
	_, err := config.Load(nil, io.Discard)
	if err == nil {
		t.Fatal("expected error, got nil")
	}
	msg := err.Error()
	for _, want := range []string{
		"public-url",
		"forgejo-url",
		"forgejo-oauth-client-id",
		"forgejo-oauth-client-secret",
	} {
		if !strings.Contains(msg, want) {
			t.Errorf("error message missing %q: %s", want, msg)
		}
	}
}

func TestLoad_InvalidIssuerURL(t *testing.T) {
	cases := []struct {
		name string
		url  string
		want string
	}{
		{"bad_scheme", "ftp://example.com", "scheme must be http or https"},
		{"http_non_loopback", "http://example.com", "http scheme only allowed for loopback"},
		{"no_host", "http:///path", "missing host"},
		{"no_scheme", "example.com", "scheme must be http or https"},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			clearEnv(t)
			args := validBaseArgs(t)
			// Replace the public-url value in args:
			for i, a := range args {
				if a == "--public-url" && i+1 < len(args) {
					args[i+1] = tc.url
				}
			}
			_, err := config.Load(args, io.Discard)
			if err == nil || !strings.Contains(err.Error(), tc.want) {
				t.Errorf("want error containing %q, got %v", tc.want, err)
			}
		})
	}
}

func TestLoad_IssuerURL_LoopbackHTTPAllowed(t *testing.T) {
	// Local development should not require a TLS cert. Validate that the
	// loopback escape hatch works for the three canonical forms.
	for _, host := range []string{"http://localhost:8080", "http://127.0.0.1", "http://[::1]:9000"} {
		t.Run(host, func(t *testing.T) {
			clearEnv(t)
			args := validBaseArgs(t)
			for i, a := range args {
				if a == "--public-url" && i+1 < len(args) {
					args[i+1] = host
				}
			}
			if _, err := config.Load(args, io.Discard); err != nil {
				t.Errorf("loopback http should be allowed, got: %v", err)
			}
		})
	}
}

func TestLoad_InvalidStorePath(t *testing.T) {
	t.Run("empty", func(t *testing.T) {
		clearEnv(t)
		args := validBaseArgs(t)
		for i, a := range args {
			if a == "--store-path" && i+1 < len(args) {
				args[i+1] = ""
			}
		}
		_, err := config.Load(args, io.Discard)
		if err == nil || !strings.Contains(err.Error(), "store-path") {
			t.Errorf("want store-path error, got %v", err)
		}
	})
	t.Run("nonexistent_parent", func(t *testing.T) {
		clearEnv(t)
		args := validBaseArgs(t)
		bogus := filepath.Join(t.TempDir(), "definitely", "not", "here", "broker.db")
		for i, a := range args {
			if a == "--store-path" && i+1 < len(args) {
				args[i+1] = bogus
			}
		}
		_, err := config.Load(args, io.Discard)
		if err == nil || !strings.Contains(err.Error(), "store-path") {
			t.Errorf("want store-path error, got %v", err)
		}
	})
}

func TestLoad_NumericBounds(t *testing.T) {
	cases := []struct {
		name string
		args []string
		want string
	}{
		{"max_sessions_zero", []string{"--max-sessions", "0"}, "max-sessions must be > 0"},
		{"max_sessions_negative", []string{"--max-sessions", "-5"}, "max-sessions must be > 0"},
		{"idle_timeout_zero", []string{"--session-idle-timeout", "0"}, "session-idle-timeout must be > 0"},
		{"idle_timeout_negative", []string{"--session-idle-timeout", "-10s"}, "session-idle-timeout must be > 0"},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			clearEnv(t)
			args := append(validBaseArgs(t), tc.args...)
			_, err := config.Load(args, io.Discard)
			if err == nil || !strings.Contains(err.Error(), tc.want) {
				t.Errorf("want %q, got %v", tc.want, err)
			}
		})
	}
}

func TestLoad_BadEnvParse(t *testing.T) {
	cases := []struct {
		envKey string
		value  string
		want   string
	}{
		{"FJMCP_BROKER_MAX_SESSIONS", "not-a-number", "FJMCP_BROKER_MAX_SESSIONS"},
		{"FJMCP_BROKER_IDLE_TIMEOUT", "forever", "FJMCP_BROKER_IDLE_TIMEOUT"},
		{"FJMCP_BROKER_DEBUG", "maybe", "FJMCP_BROKER_DEBUG"},
	}
	for _, tc := range cases {
		t.Run(tc.envKey, func(t *testing.T) {
			clearEnv(t)
			t.Setenv(tc.envKey, tc.value)
			_, err := config.Load(validBaseArgs(t), io.Discard)
			if err == nil || !strings.Contains(err.Error(), tc.want) {
				t.Errorf("want error containing %q, got %v", tc.want, err)
			}
		})
	}
}

func TestLoad_Help_ListsAllFlagsAndEnvVars(t *testing.T) {
	clearEnv(t)
	var buf bytes.Buffer
	_, err := config.Load([]string{"-help"}, &buf)
	if !errors.Is(err, flag.ErrHelp) {
		t.Fatalf("want flag.ErrHelp, got %v", err)
	}
	out := buf.String()

	wantFlags := []string{
		"-public-url", "-listen", "-forgejo-url",
		"-forgejo-oauth-client-id", "-forgejo-oauth-client-secret", "-forgejo-oauth-scopes",
		"-forgejo-mcp-binary", "-store-path",
		"-max-sessions", "-session-idle-timeout", "-debug",
	}
	for _, f := range wantFlags {
		if !strings.Contains(out, f) {
			t.Errorf("help missing flag %q", f)
		}
	}
	wantEnv := []string{
		"FJMCP_BROKER_PUBLIC_URL", "FORGEJO_URL",
		"FORGEJO_OAUTH_CLIENT_ID", "FORGEJO_OAUTH_CLIENT_SECRET",
		"FJMCP_BROKER_STORE", "FJMCP_BROKER_IDLE_TIMEOUT",
	}
	for _, e := range wantEnv {
		if !strings.Contains(out, e) {
			t.Errorf("help missing env var %q", e)
		}
	}
}