// Package config loads and validates teabot's daemon configuration and the
// per-personality tea config files it references.
package config

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"gopkg.in/yaml.v3"
)

const (
	// AppName is used for XDG config/state directory names.
	AppName = "teabot"

	// DefaultGiteaURL is the Gitea instance teabot watches by default.
	DefaultGiteaURL = "https://git.unkin.net"

	// DefaultJobImage already ships claude-code plus a Go/Node/Python/tea
	// developer toolchain, so teabot reuses it instead of building its own.
	DefaultJobImage = "git.unkin.net/unkin/agent-dev:latest"

	// DefaultPollInterval is how often each repo is polled when unset.
	DefaultPollInterval = 60 * time.Second

	// DefaultJobTimeout bounds a single Claude session.
	DefaultJobTimeout = 30 * time.Minute

	// DefaultMaxConcurrent caps simultaneously running job containers.
	DefaultMaxConcurrent = 2

	// DefaultContainerHome is the home directory inside the job image
	// (the agent-dev image runs as the unprivileged "agent" user).
	DefaultContainerHome = "/home/agent"
)

// Role describes what work a personality is allowed to perform.
type Role string

const (
	// RoleImplementer handles new issues and issue-comment follow-ups.
	RoleImplementer Role = "implementer"
	// RoleReviewer handles new pull requests and PR-comment follow-ups.
	RoleReviewer Role = "reviewer"
	// RoleBoth handles every event kind.
	RoleBoth Role = "both"
)

// Personality is a distinct Gitea bot identity backed by its own tea config
// file. Different personalities let, for example, an "implementer" account open
// PRs while a separate "reviewer" account critiques them.
type Personality struct {
	// Name is the human-readable label used in logs and prompts.
	Name string `yaml:"name"`
	// TeaConfig is the path to a tea config.yml holding this bot's Gitea
	// login (token + url + username). teabot parses it for the API token and
	// mounts it into the job container so tea acts as this identity.
	TeaConfig string `yaml:"tea_config"`
	// Role gates which event kinds this personality reacts to.
	Role Role `yaml:"role"`
	// GitName / GitEmail set the commit identity inside the container.
	GitName  string `yaml:"git_name"`
	GitEmail string `yaml:"git_email"`

	// Login is populated at load time from the parsed tea config: the Gitea
	// username. Events authored by any personality's login are ignored so the
	// bot never reacts to its own comments (loop prevention).
	Login string `yaml:"-"`
	// Token is populated at load time from the parsed tea config: the API
	// token used for polling as this identity. Never written back to disk.
	Token string `yaml:"-"`
	// URL is populated at load time from the parsed tea config: the instance
	// URL of this login.
	URL string `yaml:"-"`
}

// CanImplement reports whether the personality reacts to issue events.
func (p Personality) CanImplement() bool { return p.Role == RoleImplementer || p.Role == RoleBoth }

// CanReview reports whether the personality reacts to pull-request events.
func (p Personality) CanReview() bool { return p.Role == RoleReviewer || p.Role == RoleBoth }

// Config is teabot's top-level configuration (~/.config/teabot/config.yaml).
type Config struct {
	// GiteaURL is the base URL of the Gitea instance to poll.
	GiteaURL string `yaml:"gitea_url"`
	// Repos is the list of owner/name repositories to watch.
	Repos []string `yaml:"repos"`
	// PollInterval is the delay between poll cycles.
	PollInterval time.Duration `yaml:"poll_interval"`
	// StateDir overrides the XDG state directory used to persist processed
	// events. Empty means $XDG_STATE_HOME/teabot (default ~/.local/state/teabot).
	StateDir string `yaml:"state_dir"`
	// MaxConcurrent caps simultaneously running job containers.
	MaxConcurrent int `yaml:"max_concurrent"`
	// JobTimeout bounds a single dispatched Claude session.
	JobTimeout time.Duration `yaml:"job_timeout"`
	// JobImage is the container image each session runs in.
	JobImage string `yaml:"job_image"`
	// ContainerHome is the home directory inside JobImage that mounts target.
	ContainerHome string `yaml:"container_home"`

	// ClaudeConfigDir is the host directory holding Claude Code credentials
	// (subscription auth), mounted into each container. Empty means ~/.claude.
	ClaudeConfigDir string `yaml:"claude_config_dir"`
	// AnthropicAPIKey, when set, is injected as ANTHROPIC_API_KEY instead of
	// relying on the mounted subscription credentials.
	AnthropicAPIKey string `yaml:"anthropic_api_key"`
	// AnthropicBaseURL, when set, is injected as ANTHROPIC_BASE_URL.
	AnthropicBaseURL string `yaml:"anthropic_base_url"`

	// AllowedAuthors is the global allowlist of Gitea usernames whose issues,
	// PRs, and comments may trigger a Claude job. This is a SECURITY control:
	// jobs run with --dangerously-skip-permissions in a container whose prompt
	// is built from event text, so only trusted authors may supply that text.
	// An empty/absent allowlist is fail-closed — nothing is dispatched.
	AllowedAuthors []string `yaml:"allowed_authors"`
	// RepoAllowedAuthors optionally overrides AllowedAuthors per repository
	// (keyed by "owner/name"). A present entry fully replaces the global list
	// for that repo (even when empty, which disables dispatch for it); an
	// absent entry falls back to AllowedAuthors.
	RepoAllowedAuthors map[string][]string `yaml:"repo_allowed_authors"`

	// Personalities are the bot identities teabot dispatches as.
	Personalities []Personality `yaml:"personalities"`
}

// Load reads and validates the config at path, applying defaults and resolving
// each personality's tea config into a token/login/url.
func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading config %s: %w", path, err)
	}
	cfg := &Config{}
	if err := yaml.Unmarshal(data, cfg); err != nil {
		return nil, fmt.Errorf("parsing config %s: %w", path, err)
	}
	cfg.applyDefaults()
	if err := cfg.resolvePersonalities(); err != nil {
		return nil, err
	}
	if err := cfg.Validate(); err != nil {
		return nil, err
	}
	return cfg, nil
}

func (c *Config) applyDefaults() {
	if c.GiteaURL == "" {
		c.GiteaURL = DefaultGiteaURL
	}
	c.GiteaURL = strings.TrimRight(c.GiteaURL, "/")
	if c.PollInterval <= 0 {
		c.PollInterval = DefaultPollInterval
	}
	if c.MaxConcurrent <= 0 {
		c.MaxConcurrent = DefaultMaxConcurrent
	}
	if c.JobTimeout <= 0 {
		c.JobTimeout = DefaultJobTimeout
	}
	if c.JobImage == "" {
		c.JobImage = DefaultJobImage
	}
	if c.ContainerHome == "" {
		c.ContainerHome = DefaultContainerHome
	}
	if c.ClaudeConfigDir == "" {
		if home, err := os.UserHomeDir(); err == nil {
			c.ClaudeConfigDir = filepath.Join(home, ".claude")
		}
	} else {
		c.ClaudeConfigDir = expandHome(c.ClaudeConfigDir)
	}
	if c.StateDir != "" {
		c.StateDir = expandHome(c.StateDir)
	}
	for i := range c.Personalities {
		if c.Personalities[i].Role == "" {
			c.Personalities[i].Role = RoleBoth
		}
		c.Personalities[i].TeaConfig = expandHome(c.Personalities[i].TeaConfig)
	}
}

// resolvePersonalities parses each personality's tea config file and fills in
// its token, login, and instance URL.
func (c *Config) resolvePersonalities() error {
	for i := range c.Personalities {
		p := &c.Personalities[i]
		if p.TeaConfig == "" {
			return fmt.Errorf("personality %q: tea_config is required", p.Name)
		}
		login, err := ParseTeaConfig(p.TeaConfig, c.GiteaURL)
		if err != nil {
			return fmt.Errorf("personality %q: %w", p.Name, err)
		}
		p.Login = login.User
		p.Token = login.Token
		p.URL = login.URL
	}
	return nil
}

// Validate checks the config is internally consistent and usable.
func (c *Config) Validate() error {
	if len(c.Repos) == 0 {
		return fmt.Errorf("no repos configured")
	}
	for _, r := range c.Repos {
		if !strings.Contains(strings.Trim(r, "/"), "/") {
			return fmt.Errorf("repo %q must be in owner/name form", r)
		}
	}
	if len(c.Personalities) == 0 {
		return fmt.Errorf("at least one personality is required")
	}
	seen := map[string]bool{}
	var haveImpl, haveReview bool
	for _, p := range c.Personalities {
		if p.Name == "" {
			return fmt.Errorf("personality with empty name")
		}
		if seen[p.Name] {
			return fmt.Errorf("duplicate personality name %q", p.Name)
		}
		seen[p.Name] = true
		switch p.Role {
		case RoleImplementer, RoleReviewer, RoleBoth:
		default:
			return fmt.Errorf("personality %q: invalid role %q", p.Name, p.Role)
		}
		if p.Token == "" {
			return fmt.Errorf("personality %q: no token found in tea config", p.Name)
		}
		if p.Login == "" {
			return fmt.Errorf("personality %q: no username found in tea config", p.Name)
		}
		haveImpl = haveImpl || p.CanImplement()
		haveReview = haveReview || p.CanReview()
	}
	if !haveImpl {
		return fmt.Errorf("no personality can implement (role implementer or both)")
	}
	if !haveReview {
		return fmt.Errorf("no personality can review (role reviewer or both)")
	}
	return nil
}

// BotLogins returns the set of Gitea usernames belonging to configured
// personalities, used to skip events the bot authored itself.
func (c *Config) BotLogins() map[string]bool {
	m := make(map[string]bool, len(c.Personalities))
	for _, p := range c.Personalities {
		if p.Login != "" {
			m[p.Login] = true
		}
	}
	return m
}

// AllowedAuthorsFor returns the effective author allowlist for a repo: the
// per-repo override when one is configured (even if empty), otherwise the
// global list.
func (c *Config) AllowedAuthorsFor(repo string) []string {
	if c.RepoAllowedAuthors != nil {
		if v, ok := c.RepoAllowedAuthors[repo]; ok {
			return v
		}
	}
	return c.AllowedAuthors
}

// IsAuthorAllowed reports whether login may trigger a job in repo. Matching is
// case-insensitive (Gitea usernames are unique case-insensitively). An empty
// effective allowlist denies everyone (fail-closed).
func (c *Config) IsAuthorAllowed(repo, login string) bool {
	if login == "" {
		return false
	}
	for _, a := range c.AllowedAuthorsFor(repo) {
		if strings.EqualFold(strings.TrimSpace(a), login) {
			return true
		}
	}
	return false
}

// HasAnyAllowlist reports whether any allowlist entry is configured anywhere.
// When false, teabot dispatches nothing (fail-closed) and warns at startup.
func (c *Config) HasAnyAllowlist() bool {
	if len(c.AllowedAuthors) > 0 {
		return true
	}
	for _, v := range c.RepoAllowedAuthors {
		if len(v) > 0 {
			return true
		}
	}
	return false
}

// ImplementerFor returns the personality that should handle issue work, or nil.
func (c *Config) ImplementerFor() *Personality {
	for i := range c.Personalities {
		if c.Personalities[i].CanImplement() {
			return &c.Personalities[i]
		}
	}
	return nil
}

// ReviewerFor returns the personality that should handle PR work, or nil.
func (c *Config) ReviewerFor() *Personality {
	for i := range c.Personalities {
		if c.Personalities[i].CanReview() {
			return &c.Personalities[i]
		}
	}
	return nil
}

// expandHome expands a leading ~/ to the user's home directory.
func expandHome(p string) string {
	if p == "~" || strings.HasPrefix(p, "~/") {
		if home, err := os.UserHomeDir(); err == nil {
			if p == "~" {
				return home
			}
			return filepath.Join(home, p[2:])
		}
	}
	return p
}