package config

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

	"github.com/BurntSushi/toml"
)

const (
	DefaultChangesetDir = ".stamp"
	ConfigFileName      = "stamp.toml"
)

// ConfigPath returns the path to stamp.toml inside the changeset directory.
func ConfigPath(repoRoot string) string {
	return filepath.Join(repoRoot, DefaultChangesetDir, ConfigFileName)
}

// Config is the root configuration parsed from stamp.toml.
type Config struct {
	Config   GlobalConfig `toml:"config"`
	Projects []Project    `toml:"projects"`
}

// GlobalConfig holds repo-level settings.
type GlobalConfig struct {
	BaseBranch string `toml:"base_branch,omitempty"`
}

// Project represents a single project in the monorepo.
type Project struct {
	Name      string        `toml:"name"`
	Path      string        `toml:"path"`
	Version   string        `toml:"version"`
	Changelog string        `toml:"changelog,omitempty"`
	PreTag    string        `toml:"pre_tag,omitempty"`
	Publish   PublishConfig `toml:"publish,omitempty"`
}

// PublishConfig controls what happens during stamp publish.
type PublishConfig struct {
	Tags      *bool    `toml:"tags"`
	Releases  *bool    `toml:"releases"`
	Artifacts []string `toml:"artifacts"`
}

// ChangesetDir always returns the default changeset directory.
// The config file lives inside this directory, so it is always known.
func (c *Config) ChangesetDir() string {
	return DefaultChangesetDir
}

// BaseBranch returns the configured base branch, defaulting to "main".
func (c *Config) BaseBranch() string {
	if c.Config.BaseBranch != "" {
		return c.Config.BaseBranch
	}
	return "main"
}

// FindProject returns the project with the given name, or nil if not found.
func (c *Config) FindProject(name string) *Project {
	for i := range c.Projects {
		if c.Projects[i].Name == name {
			return &c.Projects[i]
		}
	}
	return nil
}

// ProjectNames returns all project names.
func (c *Config) ProjectNames() []string {
	names := make([]string, len(c.Projects))
	for i, p := range c.Projects {
		names[i] = p.Name
	}
	return names
}

// ChangelogPath returns the path to CHANGELOG.md for a project, relative to repoRoot.
func (p *Project) ChangelogPath(repoRoot string) string {
	changelog := p.Changelog
	if changelog == "" {
		changelog = "CHANGELOG.md"
	}
	return filepath.Join(repoRoot, p.Path, changelog)
}

// PublishTags returns true unless explicitly disabled.
func (p *PublishConfig) PublishTags() bool {
	return p.Tags == nil || *p.Tags
}

// PublishReleases returns true unless explicitly disabled.
func (p *PublishConfig) PublishReleases() bool {
	return p.Releases == nil || *p.Releases
}

// Load reads and validates stamp.toml from inside the changeset directory.
func Load(repoRoot string) (*Config, error) {
	path := ConfigPath(repoRoot)
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading %s: %w", path, err)
	}

	var cfg Config
	if err := toml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parsing %s: %w", path, err)
	}

	if err := validate(&cfg); err != nil {
		return nil, fmt.Errorf("invalid %s: %w", path, err)
	}

	return &cfg, nil
}

// Save writes the config back to stamp.toml inside the changeset directory.
func Save(repoRoot string, cfg *Config) error {
	dir := filepath.Join(repoRoot, DefaultChangesetDir)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return fmt.Errorf("creating %s: %w", dir, err)
	}
	path := ConfigPath(repoRoot)
	f, err := os.Create(path)
	if err != nil {
		return fmt.Errorf("creating %s: %w", path, err)
	}
	defer f.Close()

	enc := toml.NewEncoder(f)
	return enc.Encode(cfg)
}

func validate(cfg *Config) error {
	if len(cfg.Projects) == 0 {
		return fmt.Errorf("at least one [[projects]] entry is required")
	}

	seen := map[string]bool{}
	for i, p := range cfg.Projects {
		if p.Name == "" {
			return fmt.Errorf("projects[%d]: name is required", i)
		}
		if seen[p.Name] {
			return fmt.Errorf("projects[%d]: duplicate project name %q", i, p.Name)
		}
		seen[p.Name] = true
		if p.Version == "" {
			return fmt.Errorf("project %q: version is required", p.Name)
		}
	}
	return nil
}