package releasekit

import (
	"context"
	"fmt"
	"io"

	"gitea.maximumdirect.net/eric/ReleaseKit/internal/artifact"
	internalbuild "gitea.maximumdirect.net/eric/ReleaseKit/internal/build"
	"gitea.maximumdirect.net/eric/ReleaseKit/internal/git"
	"gitea.maximumdirect.net/eric/ReleaseKit/internal/releaseidentity"
	"gitea.maximumdirect.net/eric/ReleaseKit/internal/versioncontract"
)

// Target identifies one explicit Go operating-system and architecture pair.
type Target struct {
	OS   string // Go operating system name, such as "linux".
	Arch string // Go architecture name, such as "amd64".
}

// BuildSpec selects the application package, output name, and target pairs.
type BuildSpec struct {
	MainPackage string   // Go package path to build, such as "./cmd/app".
	BinaryName  string   // filename component used in output artifacts.
	Targets     []Target // selected target pairs; duplicates are removed in order.
}

// BuildRequest contains the source and output settings for Build.
type BuildRequest struct {
	RepositoryDir string // directory within the source Git checkout whose HEAD is recorded.
	// ModuleDir selects a repository-relative module directory; empty selects
	// the repository root.
	ModuleDir string
	Version   string    // stable vMAJOR.MINOR.PATCH value injected at link time.
	Spec      BuildSpec // application package, artifact name, and targets.
	OutputDir string    // output location; relative paths use ModuleDir and empty selects <module>/dist.
	Output    io.Writer // optional build progress destination.
}

// BuildArtifact identifies one generated binary and its SHA-256 digest.
type BuildArtifact struct {
	Path     string // absolute path to the generated binary.
	Filename string // generated filename.
	Target   Target // Go target used for this artifact.
	SHA256   string // lowercase hexadecimal digest of the complete file.
}

// BuildResult describes the source and artifacts reached by Build.
type BuildResult struct {
	RepositoryDir   string // absolute source repository path.
	ModuleDir       string // absolute selected module directory.
	ModulePath      string // selected module's declared Go path.
	Tag             string // complete tag derived for this version.
	CandidateCommit string // Git HEAD observed when the build started.
	// SourceVerified reports clean source and the same HEAD observed before and
	// after a completed build. It is required for binary delivery, not an attestation.
	SourceVerified bool
	Version        string          // requested injected version.
	MainPackage    string          // Go package path built.
	BinaryName     string          // artifact name prefix.
	OutputDir      string          // resolved output directory.
	Targets        []Target        // normalized target pairs.
	Artifacts      []BuildArtifact // completed output files, including partial success.
	Compiler       string          // output of the selected local Go toolchain's version command.
}

// Build resolves the selected module's working-tree identity, then compiles the
// selected targets with Version injected through buildinfo. It uses the
// available compatible local Go toolchain, applies ReleaseKit's readonly
// offline build settings, preserves effective cache and tool settings, and
// verifies the version command on the Go host before succeeding. Relative
// output paths use ModuleDir; an empty path selects its dist directory. An
// empty target set records source identity without running the Go toolchain.
// Errors return partial build facts in the result.
func Build(ctx context.Context, request BuildRequest) (BuildResult, error) {
	spec := *internalBuildSpec(&request.Spec)
	result := internalbuild.Result{Version: request.Version}
	failure := func(err error) (BuildResult, error) {
		result.Settings = artifact.NormalizeSettings(spec.MainPackage, spec.BinaryName, spec.Targets)
		return publicBuildResult(result), err
	}
	if !versioncontract.ValidStableVersion(request.Version) {
		return failure(fmt.Errorf("%w: %q", ErrInvalidVersion, request.Version))
	}
	repositoryDir, err := git.RepositoryRoot(ctx, request.RepositoryDir)
	if err != nil {
		return failure(err)
	}
	result.RepositoryDir = repositoryDir
	identity, err := releaseidentity.FromWorkingTree(ctx, repositoryDir, request.ModuleDir, request.Version)
	result.ModuleDir, result.ModulePath, result.Tag = identity.ModuleDir, identity.ModulePath, identity.Tag
	if err != nil {
		return failure(err)
	}
	result, err = internalbuild.BuildResolved(ctx, internalbuild.Request{
		Identity:  identity,
		Spec:      spec,
		OutputDir: request.OutputDir,
		Output:    request.Output,
	})
	return publicBuildResult(result), err
}

func publicBuildResult(result internalbuild.Result) BuildResult {
	public := BuildResult{
		RepositoryDir:   result.RepositoryDir,
		ModuleDir:       result.ModuleDir,
		ModulePath:      result.ModulePath,
		Tag:             result.Tag,
		CandidateCommit: result.CandidateCommit,
		SourceVerified:  result.SourceVerified,
		Version:         result.Version,
		MainPackage:     result.Settings.MainPackage,
		BinaryName:      result.Settings.BinaryName,
		OutputDir:       result.OutputDir,
		Compiler:        result.Compiler,
		Targets:         make([]Target, 0, len(result.Settings.Targets)),
		Artifacts:       make([]BuildArtifact, 0, len(result.Artifacts)),
	}
	for _, target := range result.Settings.Targets {
		public.Targets = append(public.Targets, Target{OS: target.OS, Arch: target.Arch})
	}
	for _, artifact := range result.Artifacts {
		public.Artifacts = append(public.Artifacts, BuildArtifact{
			Path:     artifact.Path,
			Filename: artifact.Filename,
			Target:   Target{OS: artifact.Target.OS, Arch: artifact.Target.Arch},
			SHA256:   artifact.SHA256,
		})
	}
	return public
}

func internalBuildSpec(spec *BuildSpec) *internalbuild.Spec {
	if spec == nil {
		return nil
	}
	result := &internalbuild.Spec{MainPackage: spec.MainPackage, BinaryName: spec.BinaryName}
	for _, target := range spec.Targets {
		result.Targets = append(result.Targets, internalbuild.Target{OS: target.OS, Arch: target.Arch})
	}
	return result
}

func internalBuildResult(result BuildResult) *internalbuild.Result {
	input := internalBuildSpec(&BuildSpec{MainPackage: result.MainPackage, BinaryName: result.BinaryName, Targets: result.Targets})
	settings := artifact.NormalizeSettings(input.MainPackage, input.BinaryName, input.Targets)
	converted := &internalbuild.Result{RepositoryDir: result.RepositoryDir, ModuleDir: result.ModuleDir, ModulePath: result.ModulePath, Tag: result.Tag, CandidateCommit: result.CandidateCommit, SourceVerified: result.SourceVerified, Settings: settings, Version: result.Version, MainPackage: settings.MainPackage, BinaryName: settings.BinaryName, OutputDir: result.OutputDir, Compiler: result.Compiler}
	for _, target := range settings.Targets {
		converted.Targets = append(converted.Targets, internalbuild.Target{OS: target.OS, Arch: target.Arch})
	}
	for _, artifact := range result.Artifacts {
		converted.Artifacts = append(converted.Artifacts, internalbuild.Artifact{Path: artifact.Path, Filename: artifact.Filename, Target: internalbuild.Target{OS: artifact.Target.OS, Arch: artifact.Target.Arch}, SHA256: artifact.SHA256})
	}
	return converted
}