using MeetingAssistant.MeetingNotes;

namespace MeetingAssistant.Workflow;

internal static class MeetingWorkflowRulesValidator
{
    private static readonly string[] SupportedTriggerKeys = ["created", "state_transition", "speaker_identified", "transcript_line"];
    private static readonly string[] SupportedConditionKeys = ["condition", "and", "or", "not"];
    private static readonly string[] SupportedStepUses =
        ["add_attendee", "remove_attendee", "add_project", "set_property", "add_context"];
    private static readonly string[] SupportedSetPropertyNames = ["title", "meeting.title", "transcript.line"];

    public static async Task<IReadOnlyList<string>> ValidateAsync(MeetingWorkflowRulesFile rulesFile)
    {
        var errors = new List<string>();
        var templateRenderer = new MeetingWorkflowTemplateRenderer();
        var templateModel = CreateValidationTemplateModel();
        for (var ruleIndex = 0; ruleIndex < rulesFile.Rules.Count; ruleIndex++)
        {
            var rule = rulesFile.Rules[ruleIndex];
            var ruleName = GetRuleName(rule, ruleIndex);
            if (rule.On.Count == 0)
            {
                errors.Add($"{ruleName} must define at least one trigger in 'on'. Supported triggers: {JoinAllowed(SupportedTriggerKeys)}.");
            }

            for (var triggerIndex = 0; triggerIndex < rule.On.Count; triggerIndex++)
            {
                ValidateTrigger(rule.On[triggerIndex], ruleName, triggerIndex, errors);
            }

            for (var conditionIndex = 0; conditionIndex < rule.If.Count; conditionIndex++)
            {
                ValidateCondition(rule.If[conditionIndex], ruleName, $"if[{conditionIndex + 1}]", errors);
            }

            if (rule.Steps.Count == 0)
            {
                errors.Add($"{ruleName} must define at least one step. Supported steps: {JoinAllowed(SupportedStepUses)}.");
            }

            for (var stepIndex = 0; stepIndex < rule.Steps.Count; stepIndex++)
            {
                await ValidateStepAsync(
                    rule.Steps[stepIndex],
                    rule,
                    ruleName,
                    stepIndex,
                    errors,
                    templateRenderer,
                    templateModel);
            }
        }

        return errors;
    }

    private static void ValidateTrigger(
        MeetingWorkflowTrigger trigger,
        string ruleName,
        int triggerIndex,
        List<string> errors)
    {
        var configuredCount = CountConfigured(
            trigger.Created is not null,
            trigger.StateTransition is not null,
            trigger.SpeakerIdentified is not null,
            trigger.TranscriptLine is not null);
        if (configuredCount == 0)
        {
            errors.Add($"{ruleName} on[{triggerIndex + 1}] must contain one supported trigger: {JoinAllowed(SupportedTriggerKeys)}.");
        }
        else if (configuredCount > 1)
        {
            errors.Add($"{ruleName} on[{triggerIndex + 1}] must contain only one trigger.");
        }
    }

    private static void ValidateCondition(
        MeetingWorkflowCondition condition,
        string ruleName,
        string path,
        List<string> errors)
    {
        var configuredCount = CountConfigured(
            !string.IsNullOrWhiteSpace(condition.Condition),
            condition.And is { Count: > 0 },
            condition.Or is { Count: > 0 },
            condition.Not is not null);
        if (configuredCount == 0)
        {
            errors.Add($"{ruleName} {path} must contain one supported condition key: {JoinAllowed(SupportedConditionKeys)}.");
            return;
        }

        if (configuredCount > 1)
        {
            errors.Add($"{ruleName} {path} must contain only one condition key.");
        }

        if (condition.And is { Count: > 0 } andConditions)
        {
            for (var index = 0; index < andConditions.Count; index++)
            {
                ValidateCondition(andConditions[index], ruleName, $"{path}.and[{index + 1}]", errors);
            }
        }

        if (condition.Or is { Count: > 0 } orConditions)
        {
            for (var index = 0; index < orConditions.Count; index++)
            {
                ValidateCondition(orConditions[index], ruleName, $"{path}.or[{index + 1}]", errors);
            }
        }

        if (condition.Not is not null)
        {
            ValidateCondition(condition.Not, ruleName, $"{path}.not", errors);
        }
    }

    private static async Task ValidateStepAsync(
        MeetingWorkflowStep step,
        MeetingWorkflowRule rule,
        string ruleName,
        int stepIndex,
        List<string> errors,
        MeetingWorkflowTemplateRenderer templateRenderer,
        MeetingWorkflowTemplateModel templateModel)
    {
        var stepPath = $"{ruleName} steps[{stepIndex + 1}]";
        var uses = step.Uses.Trim();
        if (string.IsNullOrWhiteSpace(uses))
        {
            errors.Add($"{stepPath} must define 'uses'. Supported steps: {JoinAllowed(SupportedStepUses)}.");
            return;
        }

        if (!SupportedStepUses.Contains(uses, StringComparer.OrdinalIgnoreCase))
        {
            errors.Add($"{stepPath} uses unsupported step '{uses}'. Supported steps: {JoinAllowed(SupportedStepUses)}.");
            return;
        }

        if (string.Equals(uses, "set_property", StringComparison.OrdinalIgnoreCase))
        {
            var property = step.Property ?? step.Name;
            if (string.IsNullOrWhiteSpace(property))
            {
                errors.Add($"{stepPath} must define 'property' or 'name' for set_property. Supported properties: {JoinAllowed(SupportedSetPropertyNames)}.");
            }
            else if (!SupportedSetPropertyNames.Contains(property.Trim(), StringComparer.OrdinalIgnoreCase))
            {
                errors.Add($"{stepPath} uses unsupported property '{property}'. Supported properties: {JoinAllowed(SupportedSetPropertyNames)}.");
            }
            else if (string.Equals(property.Trim(), "transcript.line", StringComparison.OrdinalIgnoreCase) &&
                !HasTranscriptLineTrigger(rule))
            {
                errors.Add($"{stepPath} can set 'transcript.line' only on rules with a transcript_line trigger.");
            }
        }

        if (step.Value is { } value &&
            MeetingWorkflowTemplateRenderer.ContainsRazorTemplateSyntax(value))
        {
            try
            {
                _ = await templateRenderer.RenderAsync(value, templateModel);
            }
            catch (Exception exception)
            {
                errors.Add($"{stepPath} has invalid Razor template in 'value' ({value}). {FormatRazorValidationMessage(exception)}");
            }
        }
    }

    private static string GetRuleName(MeetingWorkflowRule rule, int ruleIndex)
    {
        return string.IsNullOrWhiteSpace(rule.Name)
            ? $"rule[{ruleIndex + 1}]"
            : $"rule '{rule.Name}'";
    }

    private static bool HasTranscriptLineTrigger(MeetingWorkflowRule rule)
    {
        return rule.On.Any(static trigger => trigger.TranscriptLine is not null);
    }

    private static int CountConfigured(params bool[] values)
    {
        return values.Count(static value => value);
    }

    private static string JoinAllowed(IEnumerable<string> values)
    {
        return string.Join(", ", values);
    }

    private static MeetingWorkflowTemplateModel CreateValidationTemplateModel()
    {
        return new MeetingWorkflowTemplateModel(
            new MeetingWorkflowMeetingModel(
                "Validation Meeting",
                ["Ada Lovelace"],
                ["Validation Project"],
                MeetingWorkflowStateNames.ToRuleName(AssistantContextState.Transcribing)),
            new MeetingWorkflowEventModel(
                MeetingWorkflowEventType.StateTransition.ToString(),
                MeetingWorkflowStateNames.ToRuleName(AssistantContextState.CollectingMetadata),
                MeetingWorkflowStateNames.ToRuleName(AssistantContextState.Transcribing)),
            new MeetingWorkflowSpeakerModel("Ada Lovelace"),
            new MeetingWorkflowTranscriptModel(
                "[00:00:01] Ada Lovelace: Validation line.",
                "Ada Lovelace"));
    }

    private static string FormatRazorValidationMessage(Exception exception)
    {
        var message = exception.Message.Split(Environment.NewLine)[0].Trim();
        return string.IsNullOrWhiteSpace(message)
            ? "The template could not be compiled or rendered with the workflow model."
            : message;
    }
}