use crate::entity::{classify_path, EntityKind};
use crate::frontmatter::split_frontmatter_with_path;
use crate::types::*;
use std::collections::HashSet;
use std::path::Path;

#[derive(Debug, Clone)]
pub struct ValidationIssue {
    pub level: IssueLevel,
    pub field: Option<String>,
    pub message: String,
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize)]
#[serde(rename_all = "lowercase")]
pub enum IssueLevel {
    Error,
    Warning,
}

impl serde::Serialize for ValidationIssue {
    fn serialize<S: serde::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
        use serde::ser::SerializeStruct;
        let mut st = s.serialize_struct("ValidationIssue", 3)?;
        st.serialize_field("level", &self.level)?;
        st.serialize_field("field", &self.field)?;
        st.serialize_field("message", &self.message)?;
        st.end()
    }
}

/// Validate a vault file given its relative path and raw content.
pub fn validate(relative_path: &Path, content: &str) -> Vec<ValidationIssue> {
    let mut issues = Vec::new();

    // Check frontmatter exists
    let (yaml, _body) = match split_frontmatter_with_path(content, relative_path) {
        Ok(pair) => pair,
        Err(_) => {
            issues.push(ValidationIssue {
                level: IssueLevel::Error,
                field: None,
                message: "Missing or malformed frontmatter".into(),
            });
            return issues;
        }
    };

    let kind = classify_path(relative_path);

    match kind {
        EntityKind::Agent => validate_agent(yaml, &mut issues),
        EntityKind::Skill => validate_skill(yaml, &mut issues),
        EntityKind::CronActive | EntityKind::CronPaused | EntityKind::CronTemplate => {
            validate_cron(yaml, &mut issues)
        }
        EntityKind::HumanTask(_) => validate_human_task(yaml, &mut issues),
        EntityKind::AgentTask(_) => validate_agent_task(yaml, &mut issues),
        _ => {}
    }

    issues
}

fn validate_agent(yaml: &str, issues: &mut Vec<ValidationIssue>) {
    match serde_yaml::from_str::<Agent>(yaml) {
        Ok(agent) => {
            if agent.name.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("name".into()),
                    message: "Agent name is required".into(),
                });
            }
            if agent.executable.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("executable".into()),
                    message: "Agent executable is required".into(),
                });
            }
            let valid_executables = ["claude-code", "ollama", "openai-compat"];
            if !valid_executables.contains(&agent.executable.as_str())
                && !agent.executable.starts_with('/')
                && !agent.executable.contains('/')
            {
                issues.push(ValidationIssue {
                    level: IssueLevel::Warning,
                    field: Some("executable".into()),
                    message: format!(
                        "Executable '{}' is not a known executor. Expected one of: {:?} or an absolute path",
                        agent.executable, valid_executables
                    ),
                });
            }
        }
        Err(e) => {
            issues.push(ValidationIssue {
                level: IssueLevel::Error,
                field: None,
                message: format!("Invalid agent frontmatter: {e}"),
            });
        }
    }
}

fn validate_skill(yaml: &str, issues: &mut Vec<ValidationIssue>) {
    match serde_yaml::from_str::<Skill>(yaml) {
        Ok(skill) => {
            if skill.name.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("name".into()),
                    message: "Skill name is required".into(),
                });
            }
            if skill.description.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Warning,
                    field: Some("description".into()),
                    message: "Skill should have a description".into(),
                });
            }
        }
        Err(e) => {
            issues.push(ValidationIssue {
                level: IssueLevel::Error,
                field: None,
                message: format!("Invalid skill frontmatter: {e}"),
            });
        }
    }
}

fn validate_cron(yaml: &str, issues: &mut Vec<ValidationIssue>) {
    match serde_yaml::from_str::<CronJob>(yaml) {
        Ok(cron) => {
            if cron.title.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("title".into()),
                    message: "Cron title is required".into(),
                });
            }
            if cron.agent.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("agent".into()),
                    message: "Cron agent is required".into(),
                });
            }
            // Validate cron expression
            let expr = if cron.schedule.split_whitespace().count() == 5 {
                format!("0 {}", cron.schedule)
            } else {
                cron.schedule.clone()
            };
            if cron::Schedule::from_str(&expr).is_err() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("schedule".into()),
                    message: format!("Invalid cron expression: '{}'", cron.schedule),
                });
            }
        }
        Err(e) => {
            issues.push(ValidationIssue {
                level: IssueLevel::Error,
                field: None,
                message: format!("Invalid cron frontmatter: {e}"),
            });
        }
    }
}

fn validate_human_task(yaml: &str, issues: &mut Vec<ValidationIssue>) {
    match serde_yaml::from_str::<HumanTask>(yaml) {
        Ok(task) => {
            if task.title.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("title".into()),
                    message: "Task title is required".into(),
                });
            }
        }
        Err(e) => {
            issues.push(ValidationIssue {
                level: IssueLevel::Error,
                field: None,
                message: format!("Invalid task frontmatter: {e}"),
            });
        }
    }
}

fn validate_agent_task(yaml: &str, issues: &mut Vec<ValidationIssue>) {
    match serde_yaml::from_str::<AgentTask>(yaml) {
        Ok(task) => {
            if task.title.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("title".into()),
                    message: "Task title is required".into(),
                });
            }
            if task.agent.is_empty() {
                issues.push(ValidationIssue {
                    level: IssueLevel::Error,
                    field: Some("agent".into()),
                    message: "Agent name is required for agent tasks".into(),
                });
            }
        }
        Err(e) => {
            issues.push(ValidationIssue {
                level: IssueLevel::Error,
                field: None,
                message: format!("Invalid agent task frontmatter: {e}"),
            });
        }
    }
}

/// Validate that references between entities are valid.
/// Checks that agent skills and cron agents exist.
pub fn validate_references(
    vault_root: &Path,
    agent_names: &HashSet<String>,
    skill_names: &HashSet<String>,
) -> Vec<(String, ValidationIssue)> {
    let mut issues = Vec::new();

    // Check agent skill references
    let agents_dir = vault_root.join("agents");
    if let Ok(files) = crate::filesystem::list_md_files(&agents_dir) {
        for path in files {
            if let Ok(entity) = crate::filesystem::read_entity::<Agent>(&path) {
                for skill in &entity.frontmatter.skills {
                    if !skill_names.contains(skill) {
                        issues.push((
                            entity.frontmatter.name.clone(),
                            ValidationIssue {
                                level: IssueLevel::Warning,
                                field: Some("skills".into()),
                                message: format!("Referenced skill '{}' not found", skill),
                            },
                        ));
                    }
                }
            }
        }
    }

    // Check cron agent references
    let crons_dir = vault_root.join("crons/active");
    if let Ok(files) = crate::filesystem::list_md_files(&crons_dir) {
        for path in files {
            if let Ok(entity) = crate::filesystem::read_entity::<CronJob>(&path) {
                if !agent_names.contains(&entity.frontmatter.agent) {
                    issues.push((
                        entity.frontmatter.title.clone(),
                        ValidationIssue {
                            level: IssueLevel::Warning,
                            field: Some("agent".into()),
                            message: format!(
                                "Referenced agent '{}' not found",
                                entity.frontmatter.agent
                            ),
                        },
                    ));
                }
            }
        }
    }

    issues
}

use std::str::FromStr;

#[cfg(test)]
mod tests {
    use super::*;
    use std::path::Path;

    #[test]
    fn test_validate_valid_agent() {
        let content = "---\nname: test-agent\nexecutable: claude-code\n---\nBody";
        let issues = validate(Path::new("agents/test-agent.md"), content);
        assert!(issues.is_empty(), "Expected no issues: {:?}", issues);
    }

    #[test]
    fn test_validate_agent_missing_name() {
        let content = "---\nname: \"\"\nexecutable: claude-code\n---\n";
        let issues = validate(Path::new("agents/bad.md"), content);
        assert!(issues.iter().any(|i| i.field.as_deref() == Some("name")));
    }

    #[test]
    fn test_validate_missing_frontmatter() {
        let content = "No frontmatter here";
        let issues = validate(Path::new("agents/bad.md"), content);
        assert_eq!(issues.len(), 1);
        assert_eq!(issues[0].level, IssueLevel::Error);
    }

    #[test]
    fn test_validate_cron_bad_expression() {
        let content = "---\ntitle: bad\nagent: test\nschedule: \"not a cron\"\n---\n";
        let issues = validate(Path::new("crons/active/bad.md"), content);
        assert!(issues
            .iter()
            .any(|i| i.field.as_deref() == Some("schedule")));
    }
}