// Package validation provides a framework for validating cloud provider
// configurations and API credentials. It defines structured check results,
// a Check interface that providers implement, and a Runner that orchestrates
// checks and produces reports.
//
// Usage:
//
//	runner := validation.NewRunner(provider)
//	report := runner.Run(ctx)
//	fmt.Println(report.Format())
package validation

import (
	"context"
	"fmt"
	"strings"
	"time"
)

// Status represents the outcome of a single validation check.
type Status string

const (
	// Pass means the check succeeded.
	Pass Status = "PASS"
	// Fail means the check failed — configuration is invalid or credentials are bad.
	Fail Status = "FAIL"
	// Warn means the check passed but with a non-blocking issue (e.g. quota near limit).
	Warn Status = "WARN"
	// Skip means the check was not applicable (e.g. no token provided for a secondary provider).
	Skip Status = "SKIP"
	// Error means the check could not complete due to an unexpected error (network, etc.).
	Error Status = "ERROR"
)

// CheckCategory groups related checks for organized output.
type CheckCategory string

const (
	CategoryCredentials CheckCategory = "Credentials"
	CategoryConnectivity CheckCategory = "Connectivity"
	CategorySSH         CheckCategory = "SSH Keys"
	CategoryServer      CheckCategory = "Server Config"
	CategoryQuota       CheckCategory = "Quotas"
	CategoryAccount     CheckCategory = "Account"
)

// CheckResult is the outcome of a single validation check.
type CheckResult struct {
	// Name is a short identifier for the check (e.g. "token-auth", "ssh-keys").
	Name string
	// Category groups this check with related checks.
	Category CheckCategory
	// Status is the outcome.
	Status Status
	// Message is a human-readable description of the result.
	Message string
	// Detail is optional extra info (e.g. SSH key fingerprints found, quota numbers).
	Detail string
	// Duration tracks how long the check took (useful for API call timing).
	Duration time.Duration
}

// Passed returns true if the status is Pass or Warn.
func (r CheckResult) Passed() bool {
	return r.Status == Pass || r.Status == Warn
}

// Icon returns a terminal-friendly icon for the status.
func (r CheckResult) Icon() string {
	switch r.Status {
	case Pass:
		return "✓"
	case Fail:
		return "✗"
	case Warn:
		return "!"
	case Skip:
		return "—"
	case Error:
		return "⚠"
	default:
		return "?"
	}
}

// Check is a single validation step. Provider implementations register checks
// via their Checks() method. Each check should be independent — checks run
// concurrently and the failure of one should not affect others.
type Check interface {
	// Name returns a short kebab-case identifier (e.g. "token-format").
	Name() string
	// Category returns the check's grouping category.
	Category() CheckCategory
	// Run executes the check and returns the result.
	Run(ctx context.Context) CheckResult
}

// CheckFunc is a convenience type for creating checks from functions.
type CheckFunc struct {
	CategoryField CheckCategory
	NameField     string
	RunFunc       func(ctx context.Context) CheckResult
}

func (c CheckFunc) Name() string                { return c.NameField }
func (c CheckFunc) Category() CheckCategory     { return c.CategoryField }
func (c CheckFunc) Run(ctx context.Context) CheckResult { return c.RunFunc(ctx) }

// Report is the aggregate result of all validation checks for a provider.
type Report struct {
	// Provider is the name of the cloud provider that was validated.
	Provider string
	// Results contains the outcome of each check, in the order they were run.
	Results []CheckResult
	// TotalDuration is the wall-clock time for all checks combined.
	TotalDuration time.Duration
}

// Summary returns pass/fail/warn/skip/error counts.
func (r *Report) Summary() map[Status]int {
	counts := map[Status]int{
		Pass: 0, Fail: 0, Warn: 0, Skip: 0, Error: 0,
	}
	for _, res := range r.Results {
		counts[res.Status]++
	}
	return counts
}

// HasFailures returns true if any check failed or errored.
func (r *Report) HasFailures() bool {
	for _, res := range r.Results {
		if res.Status == Fail || res.Status == Error {
			return true
		}
	}
	return false
}

// AllPassed returns true if every check passed or was skipped.
func (r *Report) AllPassed() bool {
	return !r.HasFailures()
}

// ByCategory returns results grouped by category, preserving order within each group.
func (r *Report) ByCategory() map[CheckCategory][]CheckResult {
	out := make(map[CheckCategory][]CheckResult)
	for _, res := range r.Results {
		out[res.Category] = append(out[res.Category], res)
	}
	return out
}

// Format produces a human-readable terminal output of the report.
func (r *Report) Format() string {
	var b strings.Builder

	summary := r.Summary()
	fmt.Fprintf(&b, "\n  Provider Validation: %s\n", r.Provider)
	fmt.Fprintf(&b, "  %s\n", strings.Repeat("─", 50))

	// Group by category
	categories := []CheckCategory{
		CategoryCredentials, CategoryConnectivity, CategorySSH,
		CategoryServer, CategoryQuota, CategoryAccount,
	}
	seen := make(map[CheckCategory]bool)
	for _, cat := range categories {
		results := r.ByCategory()[cat]
		if len(results) == 0 {
			continue
		}
		seen[cat] = true
		fmt.Fprintf(&b, "\n  [%s]\n", cat)
		for _, res := range results {
			fmt.Fprintf(&b, "  %s %-25s %s\n", res.Icon(), res.Name, res.Message)
			if res.Detail != "" {
				fmt.Fprintf(&b, "    %s\n", res.Detail)
			}
		}
	}

	// Print any results in uncategorized groups
	for _, res := range r.Results {
		if !seen[res.Category] && len(r.ByCategory()[res.Category]) > 0 {
			fmt.Fprintf(&b, "\n  [%s]\n", res.Category)
			for _, r2 := range r.ByCategory()[res.Category] {
				fmt.Fprintf(&b, "  %s %-25s %s\n", r2.Icon(), r2.Name, r2.Message)
				if r2.Detail != "" {
					fmt.Fprintf(&b, "    %s\n", r2.Detail)
				}
			}
			seen[res.Category] = true
		}
	}

	// Summary line
	fmt.Fprintf(&b, "\n  %s\n", strings.Repeat("─", 50))
	fmt.Fprintf(&b, "  Total: %d checks in %s", len(r.Results), r.TotalDuration.Round(time.Millisecond))
	fmt.Fprintf(&b, "  |  ✓%d  ✗%d  !%d  —%d  ⚠%d\n",
		summary[Pass], summary[Fail], summary[Warn], summary[Skip], summary[Error])

	if r.HasFailures() {
		fmt.Fprintf(&b, "\n  Result: FAIL — fix the issues above before deploying\n")
	} else {
		fmt.Fprintf(&b, "\n  Result: OK — ready to deploy\n")
	}

	return b.String()
}

// Validatable is the interface that cloud provider implementations must satisfy
// to participate in the validation framework. It extends the basic Provider
// interface with structured validation support.
type Validatable interface {
	// ProviderName returns the display name of the provider (e.g. "Hetzner Cloud").
	ProviderName() string
	// Checks returns all validation checks for this provider.
	// The provider should inspect its own config to determine which checks
	// are applicable (e.g. skip SSH key checks if no token is set).
	Checks(ctx context.Context) []Check
}

// Runner executes all validation checks for a provider and produces a Report.
type Runner struct {
	provider Validatable
	timeout  time.Duration
}

// NewRunner creates a validation runner for the given provider.
func NewRunner(provider Validatable) *Runner {
	return &Runner{
		provider: provider,
		timeout:  30 * time.Second,
	}
}

// SetTimeout configures the per-check timeout. Default is 30s.
func (r *Runner) SetTimeout(d time.Duration) {
	r.timeout = d
}

// Run executes all checks and returns the aggregate report.
// Checks run sequentially for predictable output ordering.
// Each check respects the configured timeout.
func (r *Runner) Run(ctx context.Context) *Report {
	start := time.Now()

	// Collect checks
	checks := r.provider.Checks(ctx)

	report := &Report{
		Provider: r.provider.ProviderName(),
		Results:  make([]CheckResult, 0, len(checks)),
	}

	for _, check := range checks {
		// Per-check timeout
		checkCtx, cancel := context.WithTimeout(ctx, r.timeout)

		checkStart := time.Now()
		result := check.Run(checkCtx)
		result.Duration = time.Since(checkStart)

		// Ensure the result has its name/category set from the check
		if result.Name == "" {
			result.Name = check.Name()
		}
		if result.Category == "" {
			result.Category = check.Category()
		}

		cancel()
		report.Results = append(report.Results, result)
	}

	report.TotalDuration = time.Since(start)
	return report
}